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MathGroup Archive 2004

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Re: More on Delete Problems

  • To: mathgroup at smc.vnet.net
  • Subject: [mg51691] Re: More on Delete Problems
  • From: p-valko at tamu.edu (Peter Valko)
  • Date: Fri, 29 Oct 2004 03:39:31 -0400 (EDT)
  • References: <cl9t75$7nl$1@smc.vnet.net> <200410270554.BAA24546@smc.vnet.net> <clpq73$9qe$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Dear Andrej,

I do not really see why you used packed arrays here.
If your message is intended to suggest that the crash problem is
somehow related to the PackedArrays, your conclusion is premature. To
show this I do:

a = {{1., 2., 3.}, {4., 5., 6.}};
b = {{1, 0, 1}, {0, -2, 3}, {0, 1, 0}};
c = a . b
{{1., -1., 7.}, {4., -4., 19.}}
<< Algebra`AlgebraicInequalities`
Delete[c, {1, 1}]
{{-1., 7.}, {4., -4., 19.}}

Without including the "<< Algebra`AlgebraicInequalities`" line,
Mathematica crashes.

Including the "<<Algebra`AlgebraicInequalities`" line eliminated the
crash problem, but it does not mean the
"Algebra`AlgebraicInequalities" has anything to do with the root of
the problem. (I selected it because it is clearly a neutral,
ambivalent package for the given case.) My conclusion is that with
including a package (any package) more initialization is done and that
helps to avoid the root of the crash problem.

This example is good, because it is simple and reproducible and it
shows the existence of a problem (I suspect one related to dynamic
allocation of space) that might be more difficult to discover in a
real situation. It is possible, that a simple fix can be built in
temporarily into the init.m file, for instance. A light
acknowledgement and advice from somebody associated with WRI would
help us a lot, even if the disclamer ("this is not the official
opinion of my employer" might show up with it.)

Regards
Peter



Andrzej Kozlowski <andrzej at akikoz.net> wrote in message news:<clpq73$9qe$1 at smc.vnet.net>...
> Packed Arrays strike again!
> 
> Try this:
> 
> 
> In[1]:=
> a = {{1., 2., 3.}, {4., 5., 6.}};
> 
> In[2]:=
> b = {{1, 0, 1}, {0, -2, 3}, {0, 1, 0}};
> 
> In[3]:=
> c = Developer`FromPackedArray[a . b];
> 
> In[4]:=
> Delete[c, {1, 1}]
> 
> Out[4]=
> {{-1., 7.}, {4., -4., 19.}}
> 
> No crash.
> 
> Andrzej Kozlowski
> 
> Andrzej Kozlowski
> Chiba, Japan
> http://www.akikoz.net/~andrzej/
> http://www.mimuw.edu.pl/~akoz/
> 
> 
> 
> 
> On 27 Oct 2004, at 14:54, Peter Valko wrote:
> 
> > For the record:
> >
> > $Version
> > 5.0 for Microsoft Windows (June 11, 2003)
> >
> > a={{1.,2.,3.},{4.,5.,6.}}
> > b = {{1,0,1},{0,-2,3}, {0,1,0}}
> > c = a . b
> > Delete[c,{1,1}]
> >
> > crashes Mathematica on my machine, exactly as Give Effinger said.
> >
> >
> >
> >
> >
> >
> >
> >
> > Gove Effinger <effinger at skidmore.edu> wrote in message 
> > news:<cl9t75$7nl$1 at smc.vnet.net>...
> >> Here's simple code which bombs for me:
> >>
> >> a={{1.,2.,3.},{4.,5.,6.}}
> >>
> >> b = {{1,0,1},{0,-2,3}, {0,1,0}}
> >>
> >> c = a . b
> >>
> >> Delete[c,{1,1}]
> >>
> >> Why?
> >>
> >> G. Effinger
> >
> >


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