Using the "Show Buffer Allocations" tool (I forget where I got it on NI's website) there is no buffer-allocation-dot on the "Transpose 2D Array" function. This seems to imply that it is an "in place" operation.
-Jim > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Jason Dunham > Sent: Tuesday, January 20, 2004 12:12 PM > To: Simon Whitaker; Info-LabVIEW List > Subject: RE: Array Wish list > > > Well I was too lazy to do the test you performed, and I > didn't find anything on NI's web site. But I'm nearly > certain that the LV developers have said that transpose is an > inplace function at several of the NIWeek session's I've > attended. Maybe that's no longer true or maybe my memory has > turned to mush (fairly probable given my advancing years). > > It's certainly possible to transpose an array while reusing > the same buffer, you just have to make sure to move the > elements in the right order, and you need a tiny scratch > buffer. But I believe your test results. > > Maybe someone with inside knowledge will chime in here... > > Jason Dunham > SF Industrial Software, Inc. > > > -----Original Message----- > From: Simon Whitaker [mailto:[EMAIL PROTECTED] > Sent: Tuesday, January 20, 2004 2:03 AM > To: Info-LabVIEW List > Subject: Re: Array Wish list > > On Mon, 19 Jan 2004 22:42:22 -0800 Jason Dunham wrote: > > > As far as I've ever heard, the transpose arrays don't use any extra > > memory. The transpose function is done "in place". I'm sure a few > extra > > bytes are needed for temporary storage, but supposedly the > same array > > buffer is reused. I would guess that the graph transpose option is > also > > not a memory hog. > > Although a transposed array will consume the same amount of > memory as the original array, the transpose function involves > creating a new array, populating it using data from the > original array, then deleting the original. This can have a > significant effect on memory usage with a large array. > > LabVIEW stores multi-dimensional arrays as a list of data > items plus 4 bytes per dimension to store the size of that > dimension. You can therefore work out how much memory an > array will use: > > size of array item in bytes x no. items + 4 x no. dimensions > > The "no. dimensions" element becomes insignificant for large > arrays. So, an array of a million 16-bit integers will > consume around an extra 2 million bytes (about 1.9MB) during > transposition. > > You can confirm this by profiling some sample VIs, one with > transposition and one without. I created two VIs: the first > creates a 2D array containing 10,000,000 32-bit integers (10 > x 1,000,000) and writes it to an indicator. The second is a > copy of the first, with a transpose array node just before > the indicator. The first VI consumes almost exactly 40,000K > less than the second (84,000.94K vs 124,000.98K). According > to the above formula the array will consume c. 10,000,000 x > 4, = c. 39,000K. > > You may not need to worry about this memory hit if you're > transposing small arrays, but if you're transposing arrays > with many millions of elements your memory usage will > increase significantly during transposition - especially if > you're using a large data type like an extended precision float. > > All the best, > > Simon > > Simon Whitaker <[EMAIL PROTECTED]> > Software developer, Tiab Ltd > tel: +44 (0)1295 714046 > fax: +44 (0)1295 712334 > web: http://www.tiab.co.uk/ > >
