Re: [Plplot-devel] setlocale

[Phil Rosenberg]

Hi Hazen
I hadn't considered what you say about libraries. Let's rule out option 1.

Yes you are correct that drawing large numbers of lines would probably have a 
similar poor performance.

I think the act of checking the locale would be similarly slow. I don't think 
it's memory churn that is causing slowness. I think it's because checking and 
setting the locale involves checking environment variables or registry entries. 
I'm not entirely sure though.

I think if options 1 and 2 are disliked, then option 3 is probably the best 
option.

I can set things up so that the local only gets set for the first fill/line and 
is reset for the last fill/line.

Does that sound okay?

Phil



Sent from Outlook for Android

From: Hazen Babcock 
Sent: Tuesday, June 13, 2023 1:31:38 PM
To: Phil Rosenberg ; 
plplot-devel@lists.sourceforge.net 
Subject: Re: [Plplot-devel] setlocale


Hi Phil,

I don't think (1) is a good idea. It seems like this only effects
somewhat extreme plotting situations? Some of the examples also use
plshade() and they don't seem to be particularly slow.

Alan I think was concerned that the libraries that come with a driver
might change the locale. The cairo driver for example has a rather large
library behind it. This library might not change the locale, but it
would be hard to be sure, and this might change as the library changes.

Also it seems that the overhead of setting and restoring the locale
would affect any situation with a complicated plot, perhaps most easily
created using plshades, but if you tried to dray 1M lines you might see
something similar? So perhaps there are some optimizations that could be
made instead? For example we could check if the locale was already "C"
before setting it to "C" and then restoring? We could change
saved_lc_numerical_locale to a static variable (and not free it in
plrestore_locale) to reduce the amount of memory churn? We could add a
compiler flag that makes plsave_set_locale() and plrestore_locale() into
nops for those who are okay with this?

best,
-Hazen

On 6/2/23 05:55, Phil Rosenberg wrote:
> Hi Hazen, Arjen
> Thanks for the detective work - Alan has used that feature to help me in
> the past and I had totally forgotten about it.
>
> I can see Alan's intention here. In the wxWidgets driver I did similar
> things with other properties. For example I ensure the device context
> pen and brush are always set and reset during calls to the driver. This
> is so that if the user draws to the device context between calls, then
> plPlot does not cause problems for the user and visa-versa.
>
> Setting and resetting the brush was also an expensive operation, so to
> avoid those calls I have added an escape for starting and stopping
> plshade. I know that between these escapes there is no need to worry
> about setting and restoring the state.
>
> I think there are a few options, from most intrusive to least intrusive.
> 1. Undo Alan's work and make it the responsibility of the driver to
> restore the locale. This is what wxWidgets does with device context brushes.
> 2. Find where we think the locale might need saving and restoring and
> only do it for these calls. I'm not sure I like this, as it makes
> responsibility a grey area. Also I just tried 'ack locale' and 'ack
> LC_NUMERIC in the src directory and found references only in plargs.c,
> plcore.c and plctrl.c. So I don't think any drivers do actually change
> the locale.
> 3. I can add a variable to the PLStream which records when we enter and
> leave a plshade call. This can be checked during plfill calls so that
> only direct plfill calls save and restore the locale.
>
> My preference is for 1 or 3, does anyone else have a preference or other
> thought? 3 is certainly an easier change, but I'm happy to go down
> another route if people think it will be an improvement.
>
> Just to give an idea of the overall benefits here. I'm plotting data on
> a grid with millions of points. The wxWidgets driver changes I mentioned
> above and the removal of the locale save/restore and the changes I
> mentioned a few weeks ago with buffer memory, mean that instead of
> giving up after plPlot had been rendering for a few hours, the plot is
> rendered in under 2 minutes. So that's around two orders of magnitude
> speed increase at least.
>
> Phil
> 
> *From:* Arjen Markus 
> *Sent:* Friday, June 2, 2023 7:47:08 AM
> *To:* Hazen Babcock ;
> plplot-devel@lists.sourceforge.net 
> *Subject:* Re: [Plplot-devel] setlocale
> Hi Hazen, Phil,
>
> If the setting and restoring of the locale takes so much time, then
> would it be an option to use this only on the plot functions that might
> actually be affected by the locale? I have only glanced at the code and
> I have no idea how much work it would be. That would preserve the
> intended functionality though and get rid of the performance issue.
>
> Reg

Re: [Plplot-devel] setlocale

[Hazen Babcock via Plplot-devel]

Hi Phil,

I don't think (1) is a good idea. It seems like this only effects 
somewhat extreme plotting situations? Some of the examples also use 
plshade() and they don't seem to be particularly slow.


Alan I think was concerned that the libraries that come with a driver 
might change the locale. The cairo driver for example has a rather large 
library behind it. This library might not change the locale, but it 
would be hard to be sure, and this might change as the library changes.


Also it seems that the overhead of setting and restoring the locale 
would affect any situation with a complicated plot, perhaps most easily 
created using plshades, but if you tried to dray 1M lines you might see 
something similar? So perhaps there are some optimizations that could be 
made instead? For example we could check if the locale was already "C" 
before setting it to "C" and then restoring? We could change 
saved_lc_numerical_locale to a static variable (and not free it in 
plrestore_locale) to reduce the amount of memory churn? We could add a 
compiler flag that makes plsave_set_locale() and plrestore_locale() into 
nops for those who are okay with this?


best,
-Hazen

On 6/2/23 05:55, Phil Rosenberg wrote:

Hi Hazen, Arjen
Thanks for the detective work - Alan has used that feature to help me in 
the past and I had totally forgotten about it.


I can see Alan's intention here. In the wxWidgets driver I did similar 
things with other properties. For example I ensure the device context 
pen and brush are always set and reset during calls to the driver. This 
is so that if the user draws to the device context between calls, then 
plPlot does not cause problems for the user and visa-versa.


Setting and resetting the brush was also an expensive operation, so to 
avoid those calls I have added an escape for starting and stopping 
plshade. I know that between these escapes there is no need to worry 
about setting and restoring the state.


I think there are a few options, from most intrusive to least intrusive.
1. Undo Alan's work and make it the responsibility of the driver to 
restore the locale. This is what wxWidgets does with device context brushes.
2. Find where we think the locale might need saving and restoring and 
only do it for these calls. I'm not sure I like this, as it makes 
responsibility a grey area. Also I just tried 'ack locale' and 'ack 
LC_NUMERIC in the src directory and found references only in plargs.c, 
plcore.c and plctrl.c. So I don't think any drivers do actually change 
the locale.
3. I can add a variable to the PLStream which records when we enter and 
leave a plshade call. This can be checked during plfill calls so that 
only direct plfill calls save and restore the locale.


My preference is for 1 or 3, does anyone else have a preference or other 
thought? 3 is certainly an easier change, but I'm happy to go down 
another route if people think it will be an improvement.


Just to give an idea of the overall benefits here. I'm plotting data on 
a grid with millions of points. The wxWidgets driver changes I mentioned 
above and the removal of the locale save/restore and the changes I 
mentioned a few weeks ago with buffer memory, mean that instead of 
giving up after plPlot had been rendering for a few hours, the plot is 
rendered in under 2 minutes. So that's around two orders of magnitude 
speed increase at least.


Phil

*From:* Arjen Markus 
*Sent:* Friday, June 2, 2023 7:47:08 AM
*To:* Hazen Babcock ; 
plplot-devel@lists.sourceforge.net 

*Subject:* Re: [Plplot-devel] setlocale
Hi Hazen, Phil,

If the setting and restoring of the locale takes so much time, then 
would it be an option to use this only on the plot functions that might 
actually be affected by the locale? I have only glanced at the code and 
I have no idea how much work it would be. That would preserve the 
intended functionality though and get rid of the performance issue.


Regards,

Arjen

-Original Message-
From: Hazen Babcock via Plplot-devel 
Sent: Thursday, June 1, 2023 12:57 AM
To: plplot-devel@lists.sourceforge.net
Subject: Re: [Plplot-devel] setlocale

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Github has an interesting feature which lets you browse the code and see 
the last commit that touched a particular part of the code. Using that 
it looks like saving and restoring the locale was added to the functions 
in src/plcore.c by Alan on Sep 7, 2009.


The commit message:
"""
Protect all device driver calls using the (now) reentrant plsave_set_... 
...locale


and plrestore_locale. The former saves the fundamental PLplot LC_NUMERIC 
locale and then sets the LC_NUMERIC locale to "C" for everything done by