Re: Does MemoryConstrained count stack space?
- To: mathgroup at smc.vnet.net
- Subject: [mg117434] Re: Does MemoryConstrained count stack space?
- From: "Alexey Popkov" <lehin.p at gmail.com>
- Date: Fri, 18 Mar 2011 06:01:35 -0500 (EST)
Leonid,
As an illustration for the problem, try the following:
In[1]:= MaxMemoryUsed[]
MemoryConstrained[
Quiet@Module[{f, n = 0},
f[x_] := (n++; f[x + 1] + Plus @@ Table[Random[], {10^7}]);
Block[{$RecursionLimit = 3000}, f[0]]];,
90000000];
MaxMemoryUsed[]
Out[1]= 10071968
Out[3]= 290681632
You can see that MathKernel takes more than 267 Mb additional memory in peak
although only less than 90 Mb additional memory was allowed by
MemoryConstrained. This behavior is machine-dependent. Try to play with the
memory constrain if you cannot reproduce such behavior with the original
code.
My experience shows that in practice this value may be 900 Mb and more! This
often happens in complicated computations with heavy usage such functions as
NDSolve and NIntegrate.
P.S. I currently use Mathematica 7.0.1 under Windows 2000.
Alexey
----- Original Message -----
From: "Leonid Shifrin" <lshifr at gmail.com>
To: "Alexey" <lehin.p at gmail.com>; <mathgroup at smc.vnet.net>
Sent: Friday, March 18, 2011 4:05 AM
Subject: [mg117434] Re: [mg117411] Does MemoryConstrained count stack space?
> Alexey,
>
> My impression of the memory consumption by the stack has been that it is
> (usually?)
> much smaller than memory typically used for computations. In other words,
> you have
> just a relatively small amount of memory allowed to be used by the stack
> until the kernel
> crashes:
>
> In[1]:= MaxMemoryUsed[]
>
> Out[1]= 18009584
>
> In[2]:= Quiet@Module[{f, n = 0}, f[x_] := (n += 1; f[x + 1]);
> TimeConstrained[Block[{$RecursionLimit = 65000}, f[0]], 0.5, n]];
>
> In[3]:= MaxMemoryUsed[]
>
> Out[3]= 29857584
>
> It is about 10 Mb only, and on my system (AMD Phenom X6, Win7, M8.0, 8Gb
> RAM) setting the
> $RecursionLimit to a slightly larger value results in a crash for this
> particular function. Given that
> generally the Mathematica's memory-constraining functions are working
> approximately at best,
> and given also that the stack space seems to often be only a small
fraction
> of the total memory
> used in a computation, the memory-based method of avoiding crashes does
not
> seem promising
> to me.
>
> If it is the crashes that you want to prevent, I'd set a fixed finite
> $RecursionLimit, or, even better,
> look carefully at your functions to see why they need such a deep
recursion
> and whether you can
> rewrite the code to use iterations. OTOH, if you want to prevent the large
> memory consumption,
> evaluation stack seems to not be the main contributing factor. If your
goal
> is to prevent excessive
> swapping, in this thread
>
>
http://groups.google.com/group/comp.soft-sys.math.mathematica/browse_thread/thread/bc41b4a5f51fbcb8
>
> a function is developed which you may find useful.
>
> Regards,
> Leonid
>
>
> On Thu, Mar 17, 2011 at 2:34 PM, Alexey <lehin.p at gmail.com> wrote:
>
> > Hello,
> >
> > On the Documentation page for $RecursionLimit we read:
> >
> > "MemoryInUse and related functions do not count stack space. "
> >
> > And also:
> >
> > "On most computers, each level of recursion uses a certain amount of
> > stack space. $RecursionLimit allows you to control the amount of stack
> > space that Mathematica can use from within Mathematica. On some
> > computer systems, your whole Mathematica session may crash if you
> > allow it to use more stack space than the computer system allows. "
> >
> > Does MemoryConstrained count stack space? If not, is there another
> > function that fulfills the following statement taken from the
> > documentation page for MemoryConstrained:
> >
> > "MemoryConstrained generates an interrupt to stop the evaluation of
> > expr if the amount of additional memory requested during the
> > evaluation of expr exceeds b bytes."
> >
> > ?
> >
> > I mean a function that will count ALL additional memory requested
> > during evaluation, including stack space.
> >
> >
>