Re: Passing data from subvi's several levles down to top level vi
Pass REFERENCES to the front panel controls thru sub1 --> sub2 --> sub3 In sub3, use an unattached property node - pass it the reference to a specific control, and set its VALUE property to the new value. Unattached property nodes are on the VI SERVER palette.
Re: Congratulations, Dennis Knutson!
Congratulations and a big THANK YOU from all of us out here in user-land.
Re: Reading a File and by using TCP/IP transfer protocol?
If you have ONE client and ONE server machine then you don't want to have FIVE TCP connections. 1... Design a data structure. It should hold your five values, plus a timestamp, or whatever else you want. Make it a TypeDef, for ease of changes, if you want. On the server (where the data comes from): 2... I would have a single loop to collect your data and put it into this data structure, at whatever rate you need. This loop runs regardless of whether there is a TCP connection or not. It also sets a flag called NEW DATA. 3... Conn ID = invalid CONN ID (Initialize a shift reg) on 2nd WHILE loop 3... Repeat 4...If shift reg is not VALID conn ID: Wait for connection - assign conn ID else if NEW DATA flag NOT set wait 20 mSec (or something) else Flatten latest data cluster into string. Clear the NEW DATA flag. Write string to connection. 5... until done. On the client, you: 1... Open a connection. 2... S = flatten your Data Cluster into a string. 3... N = size of (S). Do not hardwire this constant, let it be figured for you. 4... Repeat 5... Read N bytes from connection. 6... Unflatten string into your data type. 7... Display, store, whatever. 8... until done. 9... Close connection. You'll have to add error checking, what to do if the connection breaks, etc. But that's the idea.
Re: Reading a File and by using TCP/IP transfer protocol?
Then I don't understand why you asked about files. The TCP/IP examples show how to transmit data blocks.
Re: write data to file periodically
The easiest way is to open (create) the file once at the beginning of the acquisition, and leave it open. You should use DENY WRITE permissions, at least, to prevent other apps from writing the file. Start with an empty array of data in a shift reg. Repeat Get new value Use BUILD ARRAY to prepend the new value to the existing array (IN FRONT OF the old data). Use ARRAY SUBSET to limit the array to 9000 samples. Use SUM ARRAY ELEMENTS to figure the sum. Use ARRAY LENGTH to find out how many you have. Divide the sum by the number N, and that's your current average. Write this directly to the file, or convert it to ASCII and write that. until done. Close file. This maintains the average, even when you have less than 9000 samples in your buffer. The DISADVANTAGE of this, is that the file is open during the whole event. You'll have to take special care if you want some other program to open the file while data is coming in. That also means that the contents of the file ON DISK are not necessarily up to date - there could be a block of data in memory that's not been written to disk yet. (Because of the OS, not because of your code).
Re: write data to file periodically
If I understand you correctly, the act of writing the file is disturbing your timing on the data-collection part. You need to have an average of the latest 9000 samples (15 * 60 * 10), and write the new average every 100 mSec. Are you opening/writing/closing the file each time? While that's the safest way (file is intact even if LabVIEW or your program crashes), it's not the fastest.
Re: I had a problem with Labview 7.0 and AI Config.
AI GROUP CONFIG is called by the higher-level AI CONFIG. You'll have to tell us what the error message is. Probably something to do with bad channel numbers.
Re: Reading a File and by using TCP/IP transfer protocol?
What specifically is your question? It's commonly done, but there's no built-in function for it. Here's one way: On the server side, you 1... Wait for connection 2... Open the file 3... Remainder = determine file size (in bytes) 4... Repeat 5...N = remainder 6...If N > 1024, N = 1024 (limit chunk size ) 7...Read N bytes from file. 8...Flatten N to a string of four bytes. 9...Write string to connection. 10... Write N bytes to connection. 11... Remainder = Remainder - N 12... until N = 0. 13... Flatten 0 to a string of four bytes. 14... Send 4-byte string (end-of-file marker). 15... Close File. 16... Close connection. On the client side, you: 1... Open connection to server. 2... Create (or overwrite) local file. 3... repeat 4...Read 4 bytes from connection. 5...Unflatten 4 bytes to I32 (N = size of chunk). 6...If N > 0 7...Read N Bytes from connection. 8...Write N bytes to file. 9... until N=0, or error. 10... Close connection. 11... Close file. You will need to add error-checking to that, but that's the basic idea. The chunk size can be no more than approx 1500 bytes (I forget the exact number), per IP rules. If you run both client and server on the same machine, you can use 127.0.0.1 as the IP address, and it will copy a file from one place to another. Use that to test it before bothering with two machines.
Re: Max Number of Labview objects
What sort of "objects" are you counting?
Re: Max Number of Labview objects
There is no specific limit. It depends on what kind of objects, and how much RAM your computer has. In 15 years of LabVIEW programming, I have never encountered a problem concerning too many objects. I have run out of memory when slinging 50 MByte arrays around, but not in the code itself.
Re: Prevent deletion from file dialog
If it's that critical, then test for the INI file yourself, and create it if it's not there.
Re: smtp send message.vi has a wrong send time
I would suggest looking at your computer's DST settings - perhaps you have set the clock ahead but not turned on DST. If so, the conversion to GMT and back will not be correct.
Re: Constructing an image in real time
You don't say what the data represents. Is it 3-channel RGB? Is it intensity? You can use the intensity graph to show an X vs. Y vs. Intensity image. If you have a monochrome camera, that makes a fine image - just set your min and max colors to be black and white. If you mean RGB, one way is to scale all three components into U8s (0..255) Combine them into an array of I32s, then use FLATTEN PIXMAP to convert them into an image to feed to a PICTURE indicator. You can then get the complete image data from the picture and save as PNG / JPG / BMP.
Re: Constructing an image in real time
Use the AI CONFIG to set up your acquisition. Use AI CLOCK config to set up your timing. Use AI TRIGGER CONFIG to set up your trigger. Use AI CONTROL to start the DAQ (use TOTAL SCANS TO ACQUIRE = 0 for unlimited scanning. repeat (While loop) Use AI READ with a NUMBER of SCANS TO READ = 0. This tells you the backlog (how many scans in the buffer) Use AI READ with NUMBER OF SCANS TO READ = to the backlog number from above. (this empties the buffer) Process the scans received into your image - append to previous data and re-display. If you are doing a fixed number of scans, add this backlog number to the total done so far, and see if you're done. If you're doing continuous, skip this step. Wait 100 mSec if you can, 10 mSec if you can't. Loop (until # scans done >= # scans wanted OR Quit button, whatever). Use AI CONTROL to stop the DAQ. The idea is that the DAQ operation happens in the background. You just ask how many are available, and then read that many and use them. You wait 100 mSec to allow the display update to happen.
Re: how to use notifiers?
So what happens when you put WAIT functions in the loops?
Re: how to use notifiers?
I would suggest using a WAIT function for 100 mSec or so in the main loop. If you don't have that, the main loop will poll your button at a million times per second or more. There's no need to poll the thing that fast - it will starve any other loops. It means that you will respond to the QUIT button at most 100 mSec later - not a big deal, usually.
Re: write jpeg.vi path issue
I browsed for the unix folder using safari.=A0 If you tried what I suggested, you might have better luck.
Re: Reading a file in a CIN
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I'm not sure if it will help or not, but I have attached the detailed
instructions I wrote up when wrestling with this last year.
I needed C++ in a DLL (not CIN), and detailed the steps to get there.
If CINRun is unresolved, you're not including the library in the
library list.
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HOW THE DLL "XX.dll" WAS BUILT:
1... In Visual C++ 6.0, select File | New | Projects | Win32 DLL. Give it a name,
choose a location, select CREATE NEW WORKSPACE, and then OK. On the next page, select
CREATE EMPTY DLL.
--- this creates a folder with a skeleton project in it.
2... In LabVIEW, create a VI with the inputs and outputs corresponding to the DLL's
inputs and outputs. Put a CALL LIBRARY function on the diagram.
3... Pop up on the CALL LIBRARY node and select CONFIGURE to get a dialog box. Leave
the LIBRARY NAME field blank for now. Enter a function name and select C as the
calling convention.
4... Change the words "return type" to "error", or some descriptive name. Set the
TYPE selector to NUMERIC, and the DATA TYPE selector to SIGNED 32-BIT INTEGER. This
establishes the return type of your C function (in the DLL).
5... Add parameters, set their TYPES and DATA TYPES and pass BY VALUE or BY REFERENCE
as needed. For XX, I chose:
errorCode Numeric Signed 32-bit integer
MachineName String String Handle
ProgramName String String Handle
ErrorMessageString String Handle
ChannelTags Adapt To Type Handles By Value
6... Check the FUNCTION PROTOTYPE field to verify it looks correct.
7... Click OK, and the CALL LIBRARY node changes to match your settings.
8... Wire the inputs and outputs to the CALL LIBRARY node.
9... Save the VI in the project directory.
10.. Pop up on the CALL LIBRARY node, and choose CREATE C FILE. Change the extension
to .CPP if needed, and save the file in the project directory. Quit LabVIEW if you
want.
11.. Open the DSW file in Visual C++.
12.. Select PROJECT - ADD FILES - and add the C (or CPP file) you just created.
13.. Select PROJECT - ADD FILES - and add LABVIEW.LIB (from the LabVIEW CINTOOLS
folder), if you need manager functions.
14.. Choose PROJECT - SETTINGS - ALL CONFIGURATIONS - C++ - PREPROCESSOR and enter the
full path to the CINTOOLS directory in the ADDITIONAL INCLUDE DIRECTORIES field.
15.. Choose PROJECT - SETTINGS - ALL CONFIGURATIONS - CODE GEN and select STRUCT
ALIGNMENT = 1 BYTE
16.. Choose PROJECT - SETTINGS - DEBUG CONFIGURATION - choose DEBUG MULTITHREADED DLL
in the USE RUNTIME LIBRARY selector. If you use DCOM (OLE between machines), enter the
following after the last /D entry in PROJECT OPTIONS: |/D "_WIN32_DCOM" | (not
including the | marks)
17.. Choose PROJECT - SETTINGS - RELEASE CONFIGURATION - choose MULTITHREADED DLL in
the USE RUNTIME LIBRARY selector. If you use DCOM (OLE between machines), enter the
following after the last /D entry in PROJECT OPTIONS: |/D "_WIN32_DCOM" | (not
including the | marks)
18.. Open the C (or CPP) file in Visual C++. If you're using C++, put the text |extern
"C" {| just before the declaration of your function, and the text |}| immediately
after it. (not including the | marks)
19.. Put the text |_declspec(dllexport)| immediately before both the declaration and
the definition of the function. (not including the | marks)
20.. Erase the line YOUR CODE GOES HERE, and enter your code.
21.. Build the DLL. Set the BUILD - ACTIVE CONFIGURATION to RELEASE and use the DLL
in the RELEASE folder once all bugs are fixed.
22.. Open the VI again in LabVIEW and pop up on the CALL LIBRARY node to select
CONFIGURE. Enter the file name of the DLL in the LIBRARY NAME field, or BROWSE to the
version in the DEBUG (release) folder.
23.. Run the VI.
24.. The DLL is loaded when the VI is loaded, and unloaded when the VI is unloaded.
If you go back to C to make revisions, close the VI before rebuilding, or you'll get a
CAN'T WRITE TO XX.DLL FILE error.
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Re: How to turn off new LV7 Ring Control behavior?
you will need to change both the Strings and Value property node. Drat - that's the part that breaks my code. Well, it doesn't "break" , but it's now uglier than it used to be. Thanks for the info.
Re: Inherited reentrancy?
OK - that occurred to me that there could be 4 values of V, but I wasn't sure. (It's good in my case). I had always thought about it in terms of callers - there is one V for each caller instance. But if the caller is reentrant itself, then S has FOUR callers, EVEN THOUGH there are only two instances on the diagram. Thanks for your clarification.
Re: Inherited reentrancy?
OK, thanks. The confusing thing for me is that S would have FOUR callers (and thus FOUR values of V), even though there are only TWO instances of it in the code.
Inherited reentrancy?
I understand some things about reentrancy: Say my SubVI "S" has an uninitialized shift register that is supposed to remember some value "V" from one call to the next. If S is normal (not re-entrant), and S is called from two or more places, then there is only one V - each caller would interact with this same value of V. If S is reentrant, then there are TWO separate Vs - each caller would interact with its own value of V. Suppose he caller VI "C" calls S in two places - there would be two separate values of V. Suppose C is itself reentrant. Suppose there is a master VI "M" which has two calls to C. Each instance of C calls two instances of S. Are there then FOUR different values of V? In other words, does the reentrancy get passed up the chain?
How to turn off new LV7 Ring Control behavior?
I have a ring control.
While the program is running:
1... I set its strings array to { "A", "B", "C" } via property node.
2... I set its value to 1 or 2 (by selecting "B" or "C") via mouse.
3... I set its strings array to empty.
4... The control now shows a "<1>" or "<2>" in LV7, where it showed
blank previously in LV6.1 and earlier.
This messes with my program, because I don't explicitly set its value
to zero (it doesn't show "<0> - it shows blank).
Is there an INI setting or other setting that will turn off this
unwanted behavior? Or do I have to explicitly set the value to zero
each time I empty its strings?
Re: draw an angle
Not enough information - you don't say how long the angled line is to
be.
Suppose your baseline goes from {X0,Y0} to {X1,Y1}.
Your Angle point is {X2,Y2}
Your angle is A (in radians)
The cosine C = cos(A), the sine S = sin(A).
You have to pick a length L.
Then your end point {X3,Y3} would be {X2 + L * C, Y2 + L * S}.
So the 2nd line would be from {X2,Y2} to {X3,Y3}
Re: RS-232 Framing Error with HP 34401A Mulitmeter
"Framing Error" in an RS-232 context means a very specific thing - when the receiver was expecting a stop bit, the line was not in SPACE condition. This can be the result of: 1... Baud rate mismatch (although other problems would likely crop up first). 2... Data Length problem, If I send 8 data bits and you expect 7, the stop bit is in the wrong place. 3... Parity setting mismatch - If I send 7 data bits + parity and you expect 7 data bits and no parity, the stop bit is in the wrong place. 4... Mismatch in # Stop bits - If I send you 7 Data bits + parity + one stop bit, and you expect 7 data bits + parity + TWO stop bits, the second one might not be correct, although most devices do not complain about this. --- I would double-check ALL the com settings, including the # STOP BITS - that's not shown on your screenshot.
Re: measure phase difference between two pulse trains or an encoder A-B phases
Three ideas: 1... Use CTR GROUP CONFIG to set up two counters. Use CTR MODE CONFIG to set up MODE 3 (Count Continuously), using an internal clock timebase. Use CTR Control to start the counters. Periodically: Call CTR BUFFER READ to check the backlog of readings waiting. If backlog > 0, call CTR BUFFER READ to read that many readings The readings are basically timestamps of the transitions of A and B signals. Figure the phase difference by where the B transition is, in relation to two consecutive A transitions. You need a really clean signal to get past NI's persnickety front end circuit. 0 to 5 V CMOS is OK, TTL won't do it reliably. 2... Run the A and B signals into two channels of a DAQ card (or reduce the voltage and wire into the audio input port if you have stereo input). Record enough samples to get at least one cycle of each encoder line (A and B). Perform an FFT on each channel. Pick out the highest magnitude peak from the spectrum (will be fundamental frequency). Pick out the phase corresponding to that peak (for each channel) Subtract the two phase numbers. Remember that each phase is relative to the start of the recorded block, and so doesn't mean anything by itself (unless you synchronize the trigger start). 3... Run the A and B signals into two channels of a DAQ card (or reduce the voltage and wire into the audio input port if you have stereo input). Record enough samples to get at least one cycle of each encoder line (A and B). Search thru the data for two 0-->1 transitions on the A channel. Remember the sample number where they occurred. Search thru the data for a single 0-->1 transition on the B channel. Use the sample number of the B transition as a proportion of the interval between the two A transitions. My experience with optical quadrature encoders is that they vary quite a bit. One manufacturer made a cheap model that varied +/- 60 degrees from the 90 degree ideal, as it went thru one revolution. Another mfgr made one that varied less than 5 degrees.
Re: How to keep alignment in Windows LARGE and SMALL fonts
It seems your solution would be to either move the controls to allow enough space for the enlarged fonts? My solution, such as it is, is to space things so that labels with either large or small fonts work without overlapping, and while maintaining alignment with the numeric (or other) field they are labeling. Auch, talk about self modifying programs! The solution I use does not self-modify anything, but it only works if the font is "standard" size. I mentioned a possible solution involving changing label positions on the fly, but, yes, that's ugly, like I said. Or would you want NI to use the small font anyhow and ignore the font scaling factor imposed by the Control Panel settings? No, I don't - as I said before, the point of someone switching to large fonts is so they can see a larger font ! The point is, if I set label X to be 17 point, and then switch to SMALL fonts, Label X becomes 13 point without any action from me. BUT If I set label X to be 16 point, and then switch to SMALL fonts, it stays 16 point ! I was hoping for a trick (INI setting maybe ??) that would scale 16 down to 13 or 12 without explicitly doing so (via property nodes and code). I have yet to find one. Or what else would be your solution? If I had a good solution, I wouldn't be asking the question. Default font is not a fixed font. You can change that too and I do not see how it is supposed to be different than any other font in what LabVIEW should do about it. Well the question is why -IS- it treated differently?
Re: How to keep alignment in Windows LARGE and SMALL fonts
All right, well, your statement that "to change the monitor's settings for dpi from something above 100 to something below." is what strikes me as wrong. I don't think you can tell the MONITOR to change DPI for text, but not for graphics. IN ANY CASE: IT IS A FACT that on my system, if I set a label to 17 point (default size), turn off the SIZE TO TEXT attribute, RIGHT JUSTIFY it, align the bottom of it with the bottom of the 17-point numeric's text, it looks the way I want it. IT IS A FACT that if I save that VI, switch to SMALL fonts, and open it again, it still looks the way I want it. IT IS A FACT that if I ask LabVIEW what the text size is, it now says that it is 13 point. This number has automagically changed. IT IS A FACT that if I do the same experiment with 16 or 18 (or any other, I suppose) size font, the font point size does not change, and thus becomes misaligned (and ugly, IMO). Apparently there is a rule somewhere (where, exactly?) that says: if the text was stored with the default font size, and stored with a DPI that is different from the current one, then change it's font size, by the ratio of the two DPI numbers. But if the size was ANYTHING OTHER than default size, leave it alone. #1: Is that true? #2: Can I change it? I understand that the user can select 837 DPI if he wants to, and I don't expect LV to accomodate that. But the small (96 DPI) and large (120 DPI) choices are more common, I was hoping that -I- could accomodate them for -MY- customers.
Re: calibration of the voltage
Well, we know that the VOLTAGE resolution is 20 V divided by 2^11 steps = 0.009766 Volts per step. Suppose your LVDT produces 0-5 V for a displacement of 0-10 inches. That's a factor of 10 inches divided by 5 Volts = 2 inches per volt. Multiply 2 inches per Volt times 0.009766 Volts per step, and you get 0.019532 inches per Step - that's your displacement resolution. If you can possibly configure the DAQ card to use a 0-5 V range instead of +/- 10V, you're better off doing that. That will get you 5-mil (.004883 inches) resolution instead of 20-mils (.019532). In any case just remember: Inches VoltsInches --- x -- = --- Volt Step Step
Re: How to keep alignment in Windows LARGE and SMALL fonts
ignoring the font choice and sticking to the small fonts would e.g. be better." Well, what I don't like about that is that it doesn't respond to the user's settings. Presumably, he switched from SMALL to LARGE fonts so he could maybe see larger fonts. If the text on MY program doesn't get bigger when he does that, guess whose fault it is? Mine.
Re: How to keep alignment in Windows LARGE and SMALL fonts
the way small and large fonts work is primarily to change the monitor's settings for dpi from something above 100 to something below.=A0 This affects all graphics using text measuring system, mostly text, and decides how many pixels they use to get one mm or one inch of screen. Sorry, but that's way off the mark. Try it yourself: place a STOP button, and use the new SET WIDTH and HEIGHT to 200 pixels. The result is a button 4.5 x 4.5 mm on my screen. Save it. Change from LARGE to SMALL fonts or vice versa. Open the thing and measure it again. It's still 4.5mm by 4.5 mm - of course.
Re: calibration of the voltage
how am i wasting 2 bits. By using only one fourth of the input range, you are in effect throwing away two bits (2^2 = 4) since the full scale voltage reading is 0 to 5 volts then should it not be 5/2048 resolution. But you said the resolution of the CARD was +/- 10 Volts. The card doesn't know that you're only connecting a 0-5V signal to it. If it's configured to measure +/- 10V, then that's what it will do. Half of your measurement range is wasted because your signal can't be negative. Half of the remainder is wasted because your signal can't be above 5 Volts. although i may be wasting 1/4 of the scale You are wasting THREE fourths. but is it having an effect on the calculation as the calculations look the same even when the signal goes from 0 to 5. No - that's my point. The calculations will be the same, regardless of whether your signal goes from 0 to 5V or 0 to 10 V or -10 to 10 V. It's the range of the CARD divided by the number of different values that the CARD produces. In your case this is 20 V divided by 2^11 = 0.009766 V. If that's not clear, keep asking.
How to keep alignment in Windows LARGE and SMALL fonts
For years, I fought with LabVIEW, trying to keep things looking decent in both Windows LARGE and SMALL font sizes. By this, I mean Settings - Control Panels - Display - Settings - Advanced - General - Font Size I love to use large fonts - I run my display at 1600x1200 and it just looks better. But if you plop an indicator on a panel in LARGE fonts, save it, then open it with SMALL fonts in effect, it looks horrible. N.I. Doesn't care about this - just look at how ugly their own examples get when viewed in LARGE fonts. So I developed a method to make the bottom of the label text line up with the bottom of the numerical text, whether in LARGE fonts or SMALL. http://www.culverson.com/LVStyleGuide/ObjectLabels.html";>Click here for examples. Basically, I turn OFF the SIZE to TEXT attribute and right-justify the label (if on the left of the numeric). This works OK, except I have just discovered that it depends on the text being the default size. If I have a 17-pt numeric with a 17-point label, then they both appear as 13-pt when I switch to SMALL fonts - great -- they're still aligned. But if I have a 17-point numeric with a 16-pt label, when I switch to SMALL, the numeric shrinks to 13, but the label stays at 16, and is thus vertically misaligned with the numeric. So how can I have a 17-pt numeric with a 13-pt label, and have them BOTH shrink when I switch to SMALL fonts? I suppose I could use property nodes, and detect the switch myself, but I have 50+ of these on a single VI to do - that would be ugly to watch the labels jumping around. I suppose I could have two VIs - one for LARGE fonts and one for SMALL, but I don't want to duplicate the code. Any other ideas?
Re: calibration of the voltage
11 bits resolution (an unusual number, by the way) is equal to 2^11 = 2048 discrete values that a single reading can take. If your card has a range of +/- 10 V, then that's a 20-volt spread, divided into 2048 steps (I'll assume -1024 to +1023). That means you have a resolution of 0.009766 Volts. (20 V / 2048 steps) If you could set your card to be UNIPOLAR, it would be better, since your signal is unipolar (not negative voltage). By using a 0 to +5V signal into a -10 to +10 Volt range, you are using only one fourth of the range (wasting 2 bits). If the range is -1024 to +1023 counts, your signal is only going to range from 0 to +511. So if you had a reading of 256, for example, the voltage would be 256 * 0.009766 = 2.5000 Volts. Hope that helps.
Re: Best way to pass an array of waveforms inbetween VIs
You're probably tired of hearing me say this, but the global function idea is the best. A global variable makes a COPY of the data each time you read it. That takes time, and memory. If each of 3 window reads the global, and picks out a channel, then you've made 3 copies of the original data. Depending on your data size, that may or may not be a problem. A queue means that once you read the data, it's lost from the queue. If window A reads from the queue, that data chunk is not in the queue any longer, so Window B can't read that same data. If the main window generates the data and deposits it in a global function, then each window can ask the global function for a specific channel to display. DATA STORAGE.vi: Inputs: WRITE/read (boolean) DATA IN (2-D array of DBL, for example) Channel Index (I32) Outputs: DATA OUT: 1-D array of DBL (or waveform, maybe). Code: WHILE If WRITE/read Store DATA IN in a shift reg. else Pass Shift reg IN to Shift reg Out. Pick out channel via CHANNEL INDEX Pass selected data to DATA OUT. Loop NEVER. The purpose of the loop is just to have a shift reg. It doesn't really loop - it executes once per call.
Re: Best way to pass an array of waveforms inbetween VIs
The "problem" I mentioned won't be from the code itself. It will work just fine, insofar as it won't crash or puke or anything. But I don't know your requirements. The (potential) problem comes from this: Suppose the DAQ posts new data every 1000 mSec. Suppose each window replots every 1000 mSec. Unless you synchronize things, you have the potential for one window to show data from the latest DAQ operation, and another to show data from the time before. In other words, the execution order might go: 1... Window A replots from Data Source. 2... Main updates Data Source with new data. 3... Window B replots from Data Source. So the data shown in window A was not taken at the same time as the data shown in window B. Whether that's a problem in your situation or not - I can't say. I have a solution, if you need it. Guess what? It involves occurrences !
Re: Best way to pass an array of waveforms inbetween VIs
No. Do NOT make it re-entrant. Your read and write operations should be quick. Assuming you don't have any issues about exact synchronicity between the windows, you're good to go.
Re: Best way to pass an array of waveforms inbetween VIs
this global function it will simply be a VI Correct. that is not reentrant Correct. that I will stick on every plot Correct. and the main form. Correct. So I would have the main form contiously aquiring this data and writing to the global function?=A0 Correct.
E-mail VIs - how to authenticate?
I am writing a proposal to add an e-mail notification feature to a DAQ app. In looking at the examples, sending the message seems simple enough EXCEPT I know my own e-mail provider requires authentication to send any e-mail ([EMAIL PROTECTED] spammers!). There is a separate password that is sent before the message itself is sent. If the password is wrong, the message is not sent. I see no place for this in the "SMTP Email Send Message (Small)" or the "SMTP Email Send Message" VIs. So what happens if my client uses this and his server requires a password? Does he get a dialog asking for it? Does it reject all messages? The help docs don't.
Re: Best way to pass an array of waveforms inbetween VIs
OK, the WAIT ON OCCURRENCE will solve that for you. They have a TIMEOUT input. Set it to 500 mSec or something, and that thread will not occupy the CPU until A) triggered, or B) timed out. You can tell the difference from the output and respond accordingly.
Re: Best way to pass an array of waveforms inbetween VIs
My guess is you have missed something. If the graph windows are waiting on occurrences, they should be waiting most of the time, I would think. If you have no signal generation, then I presume you have no updates, which means the graph windows never do anything except whatever your timeout function does. I have noticed that when I run some of my VIs my task manager says 100% of my processor is being used. This is where you need to focus: A user-interface VI, where you're mostly waiting to see if he pushed this button or that button, should use very little of the CPU. If you're polling the buttons, do so no faster than every 100 mSec. If you're using EVENT structure, it's done for you. If you have two or more parallel WHILE loops, remember that if one of them is blocked (waiting for button push), the other will still run. If it doesn't have a WAIT function in it, it will eat the CPU. The basic rule is: A while loop in a CALCULATION of some sort doesn't need a delay - LabVIEW will interrupt it when necessary. A while loop in a USER INTERFACE function (waiting on user interface actions) needs to wait about 100 mSec or so to share the CPU. The EVENT structure will help you do this - it waits until one of the events happens. You don't need to poll that button 10,000,000 times in a second. If you want to post your latest code, I'll take a look at it.
Re: Thanks a lot
It was nothing.
Re: Best way to pass an array of waveforms inbetween VIs
FYI: I just measured the SIMULATE SIGNAL express VI at 628 uSec to generate the default signal (100 samples, 1000 Hz) I just measured the SINE PATTERN vi (old standby for me) at 18 uSec (100 samples) That's 35x speed improvement. Maybe express IS your problem...
Re: Best way to pass an array of waveforms inbetween VIs
I have never used Waveform type. It does nothing for me. You are not forced to use that type - the EXPRESS VIs are for speed of CODING, not speed of execution. In the manuals for the RT (real-time) module (a project I am currently working on), it says something to the effect that you should never use any EXPRESS vis on the real-time card - they have too much overhead. Still - I find it hard to believe that 16 signal generators would bog your computer down, unless you're running on an old Apple II. By what are you judging that your computer has slowed down? What do you mean? You should be (and as a newcomer perhaps you are not) aware that it is necessary to add timing delays to loops in some situations. I have seen newbie code where someone will have a while loop waiting on a button push. That's fine, except it might eat your CPU time. Putting an indicator on the [i] variable showed that it was polling the button over 10 million times per second!! The problem with that is that the CPU is busy polling the one button, and doing nothing else. Putting a wait of 100 mSec in the loop lets somebody else use the CPU (the task that does the wait goes to sleep for 100 mSec - the CPU is available for something else), while still being reasonably responsive (100 mSec is not noticable) to the user. Perhaps you have such a situation? In short, while I know that the waveform data type adds overhead, I would look somewhere else FIRST , for ways to solve your "slow down" problem. Tell me how you measure the speed.
Re: Best way to pass an array of waveforms inbetween VIs
Occurrences have been around since LabVIEW 3, I think. Notifiers have not. I don't know who recommended Notifiers over occurrences IN GENERAL. All you're interested in is the fact that an update OCCURRED. When that happens, you will call the Data Source VI and ask for some channel's new data. A notifier has a data type and carries data when it's triggered. In this case, what would you carry via the Notifier? I suppose you could carry the whole new data array, but that's making copies of the big array again. Yuck. I suppose you could tell the Data Source that Notifier X is now assigned to channel Y, so when updated, it could poke channel Y's data into the Notifier. That's not too bad. You have to call the Data Source with a Notifier ID, and a channel ID, and a function of "Set Channel". Whenever the channel selector changed, you would do that again. Whenever the notifier fired, the data would be right there. I suppose that's workable. My idea was that each window generated an occurrence upon opening. It called the Data Source with a function of NOTIFY ME, passing its occurrence. The Data Source appends that occurrence to an internal array. When Updated, the Data Source went thru the array and triggered every occurrence (there might be 1 window or 9 windows open). When a window closed, it called the Data Source with a function of "STOP NOTIFYING ME", and the occurrence. The Data Source would find that occurrence and remove it from its list. In the Window code, there would be a WAIT ON OCCURRENCE - this would wait for 500 mSec or something. If Timed out, it just checks for the DONE button or something. If NOT timed out, it was triggered. So call the Data Source with the current channel number and replot the data you get back.
Re: E-mail VIs - how to authenticate?
Great, thanks. I'm not an expert on the low-level stuff. So I'll have to parse the RFCs and emulate what a regular mail client can do. As long as that's possible, I'm OK...
Re: E-mail VIs - how to authenticate?
Thanks for the pointer. It didn't work out of the box, but I'm still trying.
Re: Combobox pausing operation of other VIs
If LOOP A has the graphing VIs and Loop B has the UI stuff, then Loop A ought to run and run and run, whatever happens in loop B. You can prove (or disprove) this by putting an indicator on the [i] variable of your graphing loop. If it stops when you adjust the combobox, then you have some sort of (unwanted) dependency between the loops.
Re: Multiple Plots In Seperate Windows
I fixed the focus problem by changed the window property to floating.=A0 That's not a good fix - although the focus quits flashing, the windows don't - you can't control the Z-order (who's in front). Overlap the windows and see. The occurrences simply controlled the launching of the windows, not the distribution of data. Once a window was opened, the occurrence played no part until that window was closed and opened again. The key factor was that the code in each window was running at the same time as all other windows. Your scheme still has the window display new data and stop. Therefore you're tied to the fact that the parent has execution most of the time.
Re: Multiple Plots In Seperate Windows
If you have a re-entrant VI in each plot window, then they are NOT showing the same data. The re-entrant attribute means that each copy of the VI has its own data space. In your sine-wave example, the results might be the same, but it's really two (or 3, or 4...) copies of the same data - not multiple views of a single pile of data. If all your windows are identical in function (mine weren't, but in your example yours were), then you want to put as much code into a common VI as possible. I'm not sure what your end result is trying to accomplish, but if I were trying to allow each window to look at a different channel, then I would have the main store data for all channels) into the global function, and have each window call that function with a request for channel 2's data or channel 3's data or channel 2 vs. channel 3 in X-Y format. Make the global function do the work of extracting the requested data and assembling it into a plot. The plot window then just calls the global function with a request to get channel X, and puts the result into a graph. Long story short: Put as much code and data as you can into a common place, leave as little as possible in the multiple copies that are showing. really wish I could mail you a thank you card or something you have been a life saver.=A0 Thank you so much!=A0 I will keep learning so maybe one day I could help you." Your payment will be to stay on the forum and answer somebody else's questions now and then.
Re: creating enum from list
I don't think you can do that. A LabVIEW enum includes the string names as part of the data type. You cannot change the data type of a control or indicator programatically. If you use a TEXT RING or a MENU RING, then you can get approximately the same behavior - you can set the STRINGS property of either to an array of string values. The difference is that the VALUE of the control is a numeric, not an enum. If you wire the control to a CASE statement for example, the cases would be 0,1,2, where a true enum would have "A", "B", "C" cases.
Re: Multiple Plots In Seperate Windows
I don't have time to figure out xeactly what you're doing, but here's some ideas from a previous project I did - maybe they'll fit: The project had one main window, and six sub-windows. The main window had a button for each sub-window, to call it up. Each sub window ran on its own, offering a different view on live data being taken by the main. Each window operated as expected - it stays in front if you click it - you move them around like any other windows. You couldn't click the CLOSE box, but each window had its own DONE button which closed it. Here's how it worked: 1... A "Window Manager" vi was initialized (from the main) to generate six OCCURRENCEs and store them in a shift reg. 2... A "Window Launcher" vi is started. It first calls the WINDOW MANAGER to obtain the OCCURRENCE refnums, then launches six parallel WHILE loops. 3... Each WHILE loop has a WAIT ON OCCURRENCE function. It waits a specific time (500 mSec in my case). 4... If the WAIT ON OCCURRENCE timed out, we simply check the state of a global PROGRAM RUNNING variable, and loop if it's true. 5... If the WAIT ON OCCURRENCE did NOT time out, then it was triggered, and we call our particular sub-window (there's one WHILE loop for each window). The sub-windows are set to show front panel when opened, and close when done. 6... Each sub-window monitors the PROGRAM RUNNING global and stops if that is false. 7... Periodically, the six main buttons are fed to the "window manager"'s CHECK function. This checks each button, and if TRUE, calls "OPEN or MOVE to FRONT" VI with the path to the associated sub-window, and the occurrence for the associated window. 8... The OPEN or MOVE to FRONT vi opens a reference to the associated VI, and checks the FP Open property to see if it's already open. If it's already open, the FP.IsFrontmost property is set TRUE to bring it to the front (one might click on the main button while this window is hidden - this will bring it forward). 9... If the window is NOT already open, the associated occurrence is fired. The Window Launcher vi will then start it up. The windows do whatever work they need within themselves - it's not like the main is doing the plotting and sending data to the windows. It's more like the main is putting data into a common pot and whichever sub-windows are open (running) go and get it. Hope that helps.
Re: Multiple Plots In Seperate Windows
A global function is a VI whose principal job is to store some data (typically in the shift registers of a WHILE loop with LOOP set to false). At one time (LabView 2 and earlier) there were no global variables. The way you stored something for use by two or more independent VIs was to have a VI with a READ/WRITE switch input, a DATA input and a DATA output. If you called it with WRITE = TRUE, it stored the data you gave it. If you called it with WRITE = FALSE, you read out the data it had stored. Advantages: 1... You don't make copies of the data when you read it. That's important for memory usage when the data is a 200x64*512 array of CDB (I've used it like that). 2... It's atomic. If you want to store 6 separate items into six globals, you have the problem of knowing when ALL items have changed. Whatever reads them might read them during your change, and read 3 old values and 3 new ones. The global function is guaranteed to deliver the data as a set. 3... You can add functionality. I like to encapsulate things - for example: a config file handler. I like to have a handler (global function) for each type of config file. It has a FUNCTION input, which typically has functions like INIT, SET DEFAULT, READ FILE, WRITE FILE, COMPARE, and so on. The actual config is stored by this VI (in a shift reg, natch). Anybody who wants to deal with a config file calls this VI. That way, anytime I need to change something involving a config file, I have ONE and ONLY ONE place to go. In my multi-window project, I used a global function to create, store, and manage the occurrences.
Re: Multiple Plots In Seperate Windows
Occurrence refnum controls are on the REFNUM palette - you can pass them thru connectors, or make globals out of them. Or you can pop up on the GENERATE OCCURRENCE terminal and choose CREATE INDICATOR or CREATE CONTROL. The Shift Reg. is just a place to store them. You could probably use global variables in this case and be OK. (A global function can store things in a shift reg and have advantages: it's inherently atomic - and if the data is large, a shift reg uses less memory than global variables (no unnecessary copies made). In this case those advantages are probably not relevant. I have a tendency to encapsulate everything.
Re: Multiple Plots In Seperate Windows
why do you put them in a shift register?" Also, at the time, I didn't realize that Occurrences were special, in that a given instance of the GENERATE OCCURRENCE function will always refer to the same occurrence, even if it's been called before. In otherwords, the function that generated them didn't NEED to store them. For this reason, you can't make an array of refnums by using GENERATE OCCURRENCE inside a loop - the array of refnums will all refer to the same occurrence.
Re: Multiple Plots In Seperate Windows
The way I have wrote it causes the windows to lose and gain focus as expected.=A0 Does anyone know how to stop the focus from constantly changing?=A0 The focus is changing because the execution is changing (in the same thread). You have the VI with the graph execute, and then quit. This will lose focus. My occurrence-based scheme had all child windows executing at the same time (different threads). This meant that the window on top had focus - no other window would have it until you clicked on that window (and brought it forward). Hope that helps.
Re: Multiple Plots In Seperate Windows
You have a rather hairy state machine going on (I looked at your code again). The difference I see is that you have ONE button which spawns window #1 or window #2 or window #3, depending on who's up already. But the logic to support that is part of the polling process of every loop. My app had one button for each window (each window was different). My reason for using occurrences was to eliminate all execution paths between the main and child windows. In other words the main didn't CALL the child directly, so therefore, they became parallel independent processes. This led to the correct behavior as far as windows on top, who has focus, etc. There are probably other ways to do it - VI server, for one. I did this project in 6.0 and didn't know about VI Server then.
Re: Multiple Plots In Seperate Windows
thats really similar to what I am doing its just that my main form sends data which is causing the flashing.=A0 --- I would suggest putting the data into a separate global function (better than global variable for non-trivial amounts of data), and letting the "slaves" pull it out. At least that's what I did. This design is a great idea.=A0 I can't send the code, as it was contract labor. Thanks a MILLION for your help and time!" Please send check for one MILLION to: ;->
Re: How can I define where my program opens a dialogue (for example in the middle of the monitor)?
Are you using the standard SAVE dialog? Or are you using a custom VI
as a dialog?
If you're using the standard box, you can't change its location. You
could move the window that calls it (the one with the info you want to
see). Make it bigger, move the buttons to the outside edge, whatever.
You could actually move it (record it's window position, set new
position to 0,0, run dialog, restore original position), although
that's a bit jarring. You could suggest a file name using the info
("Run13 High Speed.txt" or something). You could put the info into
the prompt ("Please save the data for the high-speed run13").
If you are using a custom VI as a dialog, then you're free to move it
(set its position) wherever. You could copy the info from the calling
VI and display it on the SAVE dialog.
Hope there's an idea you can use in there.
Re: write jpeg.vi path issue
made sure that I used=A0 backslashes in the path for the write jpeg vi for the unix server. Backslashes are a Windows separator - it's not universal. Mac uses ":" as the separator (for historical reasons - even though it's "/" in the Mac command line. You need to compose your path using colons, not backslashes. Suggestion: 1... Manually move a file to the unix server, where you want to put your JPEG. 2... Put a PATH control on a new VI. 3... Use the BROWSE button to browse to the unix folder and choose the file you manually put there. (you have to mount the volume first). 4... Compose your path to look like what you see in that PATH control.
Re: musica
Ruido.
Re: Conditionally capturing certain data while continuously acquiring data
Your XY Chart only shows the most recent capture. If you want to have an array of them, you have to build an array. Put a shift register on the WHILE loop. Initialize it with an EMPTY array of X-Y pairs. Inside the CASE TRUE, append the new X-Y pair (you just captured) to the shift register left side and put the new array out to the right side Inside the CASE FALSE, pass the shift reg thru unchanged. You can plot the new array inside the TRUE case, if you're not concerned about speed (it will plot every time you click the button), or outside the while loop (it will plot only after you stop). Outside the while loop, save your data to a file.
Re: Binary newbie in need of assistance
It's not clear to me - are you reading the data from the A/D, or are you reading the data from files? If you're reading from files, then you have to know the file format. I would GUESS that the files would be an array of I16s - signed 16-bit integers, with four bits wasted on each sample. It's POSSIBLE they're packed - two 12-bit samples into 3 8-bit bytes. You can judge this from the file size, if you know this file is 1000 samples and the file size is 2000 bytes, you're ready to go - just read the file as a bytestream file of I16s, and swap bytes to get them into big-endian (standard) order. If the 1000-sample file is 1500 bytes, then they're packed - you will have to do some serious bit twiddling to unravel that - but it can be done. If the 1000-sample file is some other size, there's some sort of header included - you'll have to figure that out from documentation, or just trial and error.
Re: Query Results into drop down menu
I don't know about the database end of it, but you have to get the dates into an array of strings (one date per string). Once you have that, use a TEXT RING or MENU RING (your choice). Create a property node for it, and put your array of date strings into the STRINGS [ ] property of the control. The control's VALUE will be a number (0..N-1) meaning which data the user wants.
Re: Conditionally capturing certain data while continuously acquiring data
Your use of the terms "Waveforms" and "amplitude" implies a measurement of many samples into one number (for each channel). For example, if your signal was pure 100 Hz, 1.000 Volts peak, and you captured a 0.1 second block of that signal, then you would have 10 cycles in the capture buffer, varying from +1V to -1V. You can use the RMS function to turn that block of samples into a number of 0.707, meaning the RMS value is 0.707V (= 1.0 V peak). The basic philosophy would be: 1... Start a continuous acquisition. By specifying NUMBER oF SAMPLES = 0 in the AI-START vi, you will acquire data forever (until the buffer overflows, or until stopped). 2... Periodically (based on a timer), you ask the AI READ function to read zero samples. This does not remove data, but it does tell you how many samples are in the buffer. 3... You immediately read that many samples out of the buffer, and convert from volts to engineering units (if appropriate). 4... If you are measuring their frequency, you need to perform an FFT now. The highest peak in the magnitude of the FFT output is the dominant frequency in the signal. (Freq. of peak = Index of peak * Sample Rate / NPoints in block. 5... If you are doing FFTs, you get a big speed advantage if your block size is a power of two (128, 256, 512, 1024, etc.). If so, then replace step 3 with *-IF-* backlog >= N (power of 2) then read N points from buffer. 6... Apply your criteria - *-IF-* the button has been pressed, *-OR-* if the frequency of channel 2 is different, then compute the RMS or peak values and append to your final results array. Otherwise do nothing. If you want to detect 2-Hz changes, you need to know the rules of how FFTs work - the frequency resolution is the BIN WIDTH, which equals the sample rate divided by the number of points in the block. If you have a 1000 Hz sample rate and a 1024 point block, your resolution is 1000 / 1024 or just less than 1 Hz. But if you have a 1000 Hz sample rate and a 32 point block, your resolution is 1000 / 32 or about 30 Hz.
Re: Inverse FFT's
making my real set of data complex by adding an imaginary part equal to zero. Not sure why you're doing that instead of usinig REAL FFT and INVERSE REAL FFT. Are you sure you're generating the imaginary array the same length as the real array?
Re: Inverse FFT's
I just ran your problem waveform through REAL FFT and INVERSE REAL FFT, subtracted the difference and got an error of 7 e-11 on the DC term, and all other errors are on the order of e-14. LabVIEW 7 Mac OS X
Re: LabView Object Speed Specs
BE AWARE OF WHAT YOU'RE MEASURING. I just took my own advice. I re-measured the ADD operation by putting 10 ADDS into the frame 4 loop instead of 1 I get a loop time of 39.4 nanoseconds,meaning an add time of 3.94 nSec. I guess the original estimate (discarding the output) was better. My guess is that for the primitive functions like Add, Multiply, etc., it's faster to just do it than to decide if you need to or not. But I have seen certain functions perform WAY faster if the output is not connected.
Re: How can I communicate betwen parallel asynchronous VIs?
Not sure if this will help, but here's a trick I just used. The main loop handles UI stuff - changing which channel gets plotted, such things as that. It's a WHILE loop with an EVENT structure in it. A separate WHILE loop needs to run every 1000 mSec. It reads DAQ data, calculates averages, and stores data away. I set the DAQ loop to wait on an occurrence, with a 1000 mSec timeout. Inside the DAQ loop I put a CASE structure, selected by the TIMED OUT output from WAIT ON OCCURRENCE. If the occurrence timed out, I perform the DAQ operations, and loop. If it did NOT time out, it must have been triggered, so I terminate the DAQ loop immediately. Inside the UI loop, I trigger the occurrence based on a DONE button. Outside BOTH loops, I generate an occurrence that feeds to both TRIGGER and WAIT functions in both loops. You can make THAT connection thru global variables, or pass thru connectors, with no penalty.
Re: Why timer anomalies in event structure?
< slaps head > Well, duhhh.. I should have seen that. If it's 999 mSec into the timeout when the "wait" event occurs, then it will add 200 mSec to the 999, and start another timeout counter at 1199. If that one times out, then I'm sitting at 2199 mSec between events. Sometimes I can't see the forest for the trees. Thanks,
Re: What Mac OSes will LAbview 3.1.1 work on?
< dials into the WAYBACK machine > If I remember correctly, that's a 68k-only version. I belive it required 7.0 as a minimum. So my answer would be system 7.0 - 9.1 ( I think 9.1 is 68k also).
Re: Speed Contest...Linux Vs Windows
Before you make ANY decisions about alternate platforms, the first question you should ask (and answer) is "Where is the time being spent?" The PROFILE tool can help with that. Are you initializing a new DAQ operation every time? You shouldn't. 20 RPM = 0.333 Hz = 3 Sec per rev. At 4000 clicks per rev, that's 1 click every 750 uSec. That's not unreasonable. Are you trying to react to every event? It's possible you may not need to - just read however many readings there are, process however many readings there are, and repeat. Without seeing your code, it's hard to guess whether you truly are taxing the CPU, but maybe you could elaborate. I'm in the business of making things run faster. The short answer is that you can't make the program run faster, you have to make it do less. Linux or other OS will only help if your problem is in the OS portion of your code. (disk i/o ? graphics?)
Best way to programatically re-size graphs?
I have a window that pops up, containing X-Y graphs, that are say, 600 pixels wide. Under some circumstances, I want to reduce this to say, 400 pixels, and uncover a cluster of numeric displays occupying the other space. I would like to set the BOUNDS.WIDTH of the graph so that it extends right up to the POSITION.LEFT of the cluster. But I can't adjust the BOUNDS.WIDTH of the graph itself (that property is read-only). I can adjust the PLOT AREA.SIZE.WIDTH of the graph, which will affect the BOUNDS.WIDTH. But I can't use that for calculations, because I don't know the margin between the plot area and the graph bounds. I want it to work when the user re-sizes the window (All objects are scaled when window re-sizes). He may resize the window, close it, open it again and the size remains as he left it. That means I can't use absolute pixel values to move things around. I have thought of using decorations: a hidden rectangle that's the size of the small plot area, and another one that's the size of the large plot area. Then set the plot area's SIZE.WIDTH to the width of the small or large decoration. They decorations would scale along with everything else, and all would be OK. 1... Does anyone have a better / different idea? 2... If not, how should I get the reference to the decorations? They can't be named. Using the VI reference, I would have to pick out decorations #3 and #4 or something (there are other decorations already present). That just seems a bit fragile. How can I move these new ones to be #0, and #1 ??
Re: Best way to programatically re-size graphs?
The logic behind this is that the difference between the total bounds, and the plot area is constant. I don't think that's true, given the fact that the window may be resized, and the graphs will scale with it. I *-THINK-* I have it working using a dummy button, rather than a decoration. If the button is hidden, it still re-sizes with the window. So I made a button that was the width of the small plot area, and another which is the width of the large plot area, and hid them both. When the window pops up, I decide which I need, and set the graph's PLOT AREA to one width, or the other. When the window resizes, the button scales too, and the next time the decision is made, the buttons are the right size as well. I guess the decoration idea was a tangent.
Re: Why does priority of NON RUNNING vi affects execution time of
OK, that's farther up the CompSci tree than -I- can follow, but as long as it's a known behavior, I can deal with it. =A0 By the way, this doesn't happen at compile time as the VI doesn't need to be recompiled for this to happen, but it does happen on load. That makes sense, because in my real object the dummy caller is BROKEN and won't compile (required connections are missing), but the behavior happens anyway. I wonder what happens if the high-priority caller is loaded WHILE the low-priority system is running. Do priorities change DURING execution? No answer necessary- If I really want to know, I'll test it and find out.
Re: Why does priority of NON RUNNING vi affects execution time of
When you have a shared nonreentrant subVI, and one caller is high priority and one is lower, then the subVI's priority is boosted to match the higher of the callers. --- Notice that my later tests prove that you don't need TWO callers. The same effect is apparent with only ONE caller. To recap: here are the mysteries solved: 1... If A calls B, and B's priority is higher, a context switch overhead is incurred. 2... If A calls B, and C calls B, then B's priority is boosted, if necessary, to match the higher of A's or C's priority. 3... # 2 applies EVEN if one of the callers is not even running. It's the combination of these three that confused me. Thanks, Greg and Ben!
Re: Why does priority of NON RUNNING vi affects execution time of
When you have a shared nonreentrant subVI, and one caller is high priority and one is lower, then the subVI's priority is boosted to match the higher of the callers. --- You suggested this before and all tests seem to bear this out. but the lower priority VI will need to go through thread context switches to and from the high priority subVI calls. --- This was our inferred explanation - good to have confirmation. I'm still not sure why a priority-switch is equated to a thread switch, though. Priorities do not pipe higher octane electrons through your computer.=A0 Priorities can only speed one thing up by slowing another down. --- I understand that. What was a mystery (and is now explained) is that the subVI is treated=A0as a shared resource EVEN THOUGH there is no competition for it (only one caller). On the face of it, it doesn't make sense for priorities to be involved at all when a single call to a single VI is used. But, you have to go through the same motions, because you don't really know if another VI might call it or not. Also, what was a mystery was the fact that if A calls B, then B's priority is boosted, if necessary, to match A's. And this occurs AT COMPILE TIME, whether the A--> B call is actually executed or not. And threads add overhead, especially when not used appropriately. --- Threads only entered into this as experiments to explain what is happening. I started with everything on the default (SAME AS CALLER) thread.
Re: Why does priority of NON RUNNING vi affects execution time of
Thanks for the link, though I'm not sure it applies. 1... I'm not using RT things - there's not an RT board present. 2... These shared resources include global variables, non-reentrant subVIs,... -- So a non-reentrant subVI is a "shared resource". 3... Priority inheritance allows the lower priority thread to temporarily =93inherit=94 the time-critical priority setting, long enough to finish using the shared resource and to remove the protection. Once the protection is removed, the lower priority thread resumes its original lower priority setting and is taken off of the processor. --- I suppose the subVI could be a "shared resource", even though one of the sharers is not running. But if that's what is happening, then you are suggesting that the process of changing priorities up and back down adds 10 mSec to the execution time. --- However, the tester calls the thing 1000 times, so I suppose the extra 10 mSec is divided by 1000, so it's 10 uSec per call - that seems believeable. --- And since subroutine-priority avoids the scheduler altogether, it's not subject to this priority inversion. --- And when I made the subVI re-entrant, it's no longer a "shared resource" and is not subject to this priority inversion. --- OK, I'm convinced you're on the right track, assuming this note about RT applies to the plain LabVIEW as well.
Re: Why does priority of NON RUNNING vi affects execution time of
The problem with this idea is that in the case where I don't load the dummy caller, the resource is not "shared" - there's only one call to it! Apparently the fact that the subVI is higher priority is enough to get it to be declared "shared", even though there's no competition for it. Do you agree with that reasoning?
Re: Why does priority of NON RUNNING vi affects execution time of
I am leaning toward this being the OS related. For what it's worth, I DID verify that setting the priority of the tester to match the dummy caller restores the normal execution time. Also for what it's worth, I ran the same tests on Mac OS X. The same behavior results, except that the difference is more extreme (10 mSec --> 55 mSec). But matching priorities works there as well. More information: The dummy caller is not even necessary to prove the point - like Greg said, it is boosting the priority of the VI it calls, even though it doesn't execute. Without the dummy even loaded, if you set the priority of the time-waster VI to HIGHER than the tester, the penalty is imposed. The rule as I understand it: A time penalty is imposed when a VI calls a higher-priority VI. (Subroutine priority excepted).
Re: Why does priority of NON RUNNING vi affects execution time of
Regular VIs are greatly affected by whether the panel is in memory and whether the panel is open.=A0 I suspect that you have eliminated these effects, but it is always worth restating.=A0 After any of these changes to priorities, perform a Save All before taking any timings. --- I understand that, and yes, I did save things and close the front panels. The subVI can only be run by one of them at a time, assuming it isn't reentrant, and if its preferred priority is set lower than one of the callers, it will be boosted to match the higher of the callers. --- The subVI was set to "normal" priority, excluding the experiments. So, you're saying that the "object" subVI in question was boosted to above-normal priority because one of it's callers was above-normal. Fine. That doesn't explain why it then took LONGER to execute. Is there a penalty for calling a higher-priority VI from a lower one? Apparently so. Maybe some extra trips thru the scheduler? I didn't test it, but I'd guess from what you're saying that if I boosted the priority of the tester, the penalty would have disappeared. Regardless, I am working fine with subroutine priority, but I want to understand things better. I've read the app note (#114, I think), but I can't see a connection between the words there and my situation here.
Re: Why does priority of NON RUNNING vi affects execution time of subVI?
If I set the "wasteTime.VI" as sub-routine, the undesirable effect goes away! Hmmm - that works for me too. In the real case, the "Object" has a subVI which has a subVI. I have to set those to subroutine as well, because a subroutine cannot call a non-subroutine priority VI. But I think that's OK, in my case. If I do that, I get times of 8-9 mSec on the real object! I didn't try subroutine because I thought it would be the same as the other above-normal priorities - guess I was wrong. Still don't understand why, though. Thanks for your eyes!
Re: Why does priority of NON RUNNING vi affects execution time of subVI?
If the OBJECT is set to: the time is : RE-ENTRANT - NORMAL - SAME AS CALLER 11.2 mSec NORMAL - SAME AS CALLER 28.9 mSec RE-ENTRANT - NORMAL - OTHER1 33.8 mSec NORMAL - OTHER1 29.2 mSec All of that with the phony caller (that's not running) set to TIME CRITICAL (or anything above NORMAL). Any clues there? Looks like thread makes no difference...
Re: Why does priority of NON RUNNING vi affects execution time of subVI?
How about if everything is set for the same thread? This would rule out the thread swapping theory. --- That's where we came in. I just double checked, and everything is set to NORMAL - SAME ExeSys AS CALLER (Non re-entrant). The times are about 11.4 mSec. If I set the DUMMY priority anywhere above NORMAL, I get 28 - 29 mSec times.
Re: Why does priority of NON RUNNING vi affects execution time of subVI?
Is the "object" configured to run in the "Same thread as caller"? Yes. But that doesn't explain (to me) the connection - given that one execution path is not even running, why is the other penalized? MORE INFORMATION: If I make the object RE-ENTRANT, the execution time is back to "normal", regardless of priorities. That's not a real solution for me, as I have shift registers within the object I need to keep, but maybe it's a hint as to what's going on.
Re: Why does priority of NON RUNNING vi affects execution time of subVI?
MORE INFORMATION: If I put the "Object" VI (normal priority) in a brand-new VI, the tester shows the faster execution time. If this new VI is set to ABOVE NORMAL priority, the execution time balloons upward again. If I raise the TESTER's priority to match (or exceed) the new VI's priority, it's back down again. In other words, it looks like calling a lower priority VI from a higher priority VI puts a "fence" around that lower-priority VI, EVEN IF THE CALLER IS NOT RUNNING. Other VIs of the same lower priority suffer the penalty of that "fence".
Re: Setting a property of a substring fails only during first execution.
It fails because there is no text in the indicator the first time. You are setting the attributes BEFORE you set the text into the indicator. With no text present, you can't set SEL START or SEL END to anything but 0.
Why does priority of NON RUNNING vi affects execution time of subVI?
I'm chasing a weird timing problem. LabVIEW 7.0 + Windows 2000 I have a VI (called "the Object"), whose purpose is to store and retrieve numerical values by name. The name is hashed, converted to an array index and the values are read / written to an array slot. That all works fine. I have a tester for the Object. It generates random names and random values. starts a timer, stores the values (say 1000 of them),marks the timer, reads the values, and marks the timer again. The point is to judge the execution time of the Object. That all works fine. EXCEPT I measure a particular case at 11.44 mSec for 1000 writes. Repetitions result in numbers similar to 11.44 I then load a particular VI from a program I'm having trouble with. The trouble is it's taking more time than expected to process data. This VI is normally set to execute at TIME CRITICAL priority. This VI uses (indirectly) the Object. If I load this VI WITHOUT RUNNING IT, and run the tester, the execution time goes from 11.44 to 27.08 mSec. The VI is NOT RUNNING, yet it's presence affects the execution time of a VI it uses. If I change its priority to NORMAL or BACKGROUND, then the tester reports the shorter times (11.44 or so). If I change its priority to ANYTHING above NORMAL, I get a 27+ mSec time. I can change it back to normal, and get the "normal" execution time. Why does a given VI's priority affect it's subVI's execution time IF IT IS NOT EVEN RUNNING? And how do I fix it?
Re: create a small data base stored in a file
No, I program for a living. Everything you need is in my previous answer.
Re: create a small data base stored in a file
For something this small, use a single VI to manage it in memory:
It has a FUNCTION input, an enum with values of (INIT, READ FILE,
WRITE FILE, ADD ITEM, FIND ITEM).
It has a CLUSTER input, which is your record type {Item number, serial
number, time stamp, description}
It has a CLUSTER output, of the same type.
It has an ITEM NUMBER input, which is an integer (assuming your item
number is truly a number).
The code is a WHILE loop with the CONTINUE input wired to FALSE (it
never loops).
Inside the WHILE LOOP is a CASE statement, with the selector wired to
the FUNCTION control.
For case INIT, make an empty array of records (your cluster type) and
feed it to a shift register on the WHILE loop.
For case WRITE FILE, take the shift register input and CREATE, WRITE,
and CLOSE a file. (pass it thru to the output as well). Wire the
cluster to the DATALOG TYPE of the CREATE FILE function to create a
datalog file.
For case READ FILE, use OPEN FILE, READ FILE, and CLOSE FILE
functions, with DATALOG TYPE wired to the cluster type.
For case ADD ITEM, just append the new item (input cluster control) to
the array from the shift reg and put the array back in the shift reg.
For case FIND ITEM, just search thru the array (from the shift reg)
until you find the matching item number, then return the whole record
in the output.
You'll have to pass the left shift reg thru the case to the right
shift reg in all cases except INIT, READ FILE, and ADD ITEM.
This means the actual storage is in the shift reg, for max efficiency.
If you get beyound a hundred items, I would suggest a different FIND
ITEM technique (keep a separate list for ITEM NUMBERS and search that,
rather than the whole thing).
This assumes you have control of shutdown - any changes you make are
lost unless you call WRITE FILE afterwards.
