Re: memory management and pointers

• To: mathgroup at smc.vnet.net
• Subject: [mg27174] Re: memory management and pointers
• From: "Allan Hayes" <hay at haystack.demon.co.uk>
• Date: Fri, 9 Feb 2001 03:10:21 -0500 (EST)
• References: <95tpi7\$m0s@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Sébastien ,
Re your first example:
Try

u[[1, 1]] = 1

--
Allan
---------------------
Allan Hayes
Mathematica Training and Consulting
Leicester UK
www.haystack.demon.co.uk
hay at haystack.demon.co.uk
Voice: +44 (0)116 271 4198
Fax: +44 (0)870 164 0565

<Sebastien.deMentendeHorne at electrabel.com> wrote in message
news:95tpi7\$m0s at smc.vnet.net...
> Hi,
>
> I never heard about pointers in Mathematica but I am facing a problem
where
> it should be nice if Mathematica doesn't allow/free memory every time.
>
> For instance:
>
> u = ReplacePart[u,1,{1,1}] where u is a very big matrix
>
> As I need to do this very often in an algorithm, Mathematica spends a lot
of
> the time by:
> - creating the new object ReplacePart[u,1,{1,1}] which is as big as
> u
> - rebinding u to the new object
> - freeing the old u object
> Is it possible to ask Mathematica to do a ReplacePart directly on u
without
> all the hassle of allocation/free of memory.
>
> Another example:
>  u = u + f[u] +g[u] where u is again the big matrix
> will imply a lot of wasted time in memory problems.
>
> When Mathematica says that "u += a" is equivalent to "u = u + a" is it
true
> or almost true (difference in memory management)?
>
> Thank you very much
> Sébastien
>
>
> Sébastien de Menten de Horne      |    ELECTRABEL
> Tel:  ++32 10 48 51 76            |    R&D Energy Markets,
> Fax:  ++32 10 48 51 09            |    Traverse d'Esope, 6
> Gsm:  ++32 478 789 444            |    B-1348 Louvain-la-Neuve, BELGIUM
>

```

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