Re: How to kill slave kernel securely?
- To: mathgroup at smc.vnet.net
- Subject: [mg117448] Re: How to kill slave kernel securely?
- From: "Alexey Popkov" <lehin.p at gmail.com>
- Date: Sat, 19 Mar 2011 05:17:21 -0500 (EST)
At this moment I use Mathematica 7.0.1 under Windows. It is nice to hear
that in v.8 the memory allocator has been improved, but at this moment I
have no access to v.8. May be later... At the same time it is possible that
you just have tried not enough with other (greater) values for the memory
constrain or you should increase the value for $RecursionLimit...
Alexey
----- Original Message -----
From: "Oliver Ruebenkoenig" <ruebenko at wolfram.com>
To: "Alexey Popkov" <lehin.p at gmail.com>
Cc: "comp.soft-sys.math.mathematica" <mathgroup at smc.vnet.net>
Sent: Friday, March 18, 2011 6:28 PM
Subject: [mg117448] Re: [mg117082] How to kill slave kernel securely?
> On Fri, 18 Mar 2011, Alexey Popkov wrote:
>
> > Oliver Ruebenkoenig <ruebenko at wolfram.com> wrote:
> >> On Thu, 10 Mar 2011, Alexey Popkov wrote:
> >>> 2) My bitter experience with MemoryConstrained clearly shows that it
is
> > not
> >>> a reliable function. It practical cases when I heavily use such
> > functions as
> >>> NDSolve, NIntegrate etc. it often allows MathKernel to take for
example
> >>> 500-900 MB more that I have set. And system goes into swapping...
> >>
> >> You could forward that to the tech support for us to look at.
> >>
> >> Oliver
> >
> > I have found today a simple example when MemoryConstrained fails:
> >
> > In[1]:= MaxMemoryUsed[]
> > MemoryConstrained[
> > Quiet@Module[{f, n = 0},
> > f[x_] := f[x + 1] + Plus @@ Table[Random[], {10^7}];
> > Block[{$RecursionLimit = 3000}, f[0]]];, 90000000];
> > MaxMemoryUsed[]
> >
> > Out[1]= 10757752
> >
> > Out[3]= 291258232
> >
> > You can see that MathKernel takes more than 260 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.
>
> Actually I do not see that:
>
> Mathematica 8.0 for Linux x86 (64-bit)
> Copyright 1988-2011 Wolfram Research, Inc.
>
> In[1]:= MaxMemoryUsed[]
>
> Out[1]= 13993528
>
> MemoryConstrained[
> Quiet@Module[{f, n = 0},
> f[x_] := f[x + 1] + Plus @@ Table[Random[], {10^7}];
> Block[{$RecursionLimit = 3000},
> f[0]]];, 90000000]; MaxMemoryUsed[]
>
> Out[2]= 14521744
>
> For version 8 the memory allocator has been rewritten and improved.
>
> (What a small sentence for such a huge endeavor and such a fine execution)
>
>
> Here is another example with a lower bound
>
> MaxMemoryUsed[]/1024.^2
> MemoryConstrained[
> Quiet@Module[{f, n = 0},
> f[x_] := f[x + 1] + Plus @@ Table[Random[], {10^8}];
> Block[{$RecursionLimit = 20000}, f[0]]];, 20000000];
> MaxMemoryUsed[]/1024.^2
>
> >
> > As I said before, my experience shows that in practice the overshoot can
be
> > 900 Mb and more! This often happens in complicated computations with
heavy
> > usage such functions as NDSolve and NIntegrate inside loops.
> >
> > Alexey
> >
> >
>
> There may be various issues here, for example, NDSolve calls external
> libraries. And M- does not and can not have control over those memory
> processes. Similar issues may arise with e.g. MKL.
>
> Could you provide an example, where the overshot is 900 Mb - assuming you
> see this in V8.
>
> Oliver
>