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Re: Estimating memory usage of expressions


The object "1" and the object "list containing only the element 1" are different
in nature so it's expectable they heve different Mathematica representation
and different Memory usage.

I don't know the C representation for a Mathematica List or a Mathematica
Integer, i don't even know if they are public domain.

Anyway, if you do

ByteCount[{1}]      => 56
ByteCount[{1,2}]    => 80
ByteCount[{1,2,3}]   => 104
ByteCount[{1,2,3,4}]   => 128

you see the difference is always 24 bytes.

It tried to do a little experiment, the list data structure changes
when you add some elements :

r = Table[RandomInteger[], {i, 100}];
(ByteCount[r] - 32) / 24    => 100

r = Table[RandomInteger[], {i, 200}];
(ByteCount[r] - 32) / 24    => 200

r = Table[RandomInteger[], {i, 250}];
(ByteCount[r] - 32) /24     => 91/2       !!!!

In the last result i would expect naively a result 250,
91/2 tells me that things underwood are more sophisticated.

Hope somebody can tell you more ;-)

bye

n.






On 2010-04-08 14:02:42 +0200, Jim Lambaugh said:

> Hi
>
> Is there a way to estimate how many bytes the different expressions in
> Mathematica take from the memory? For example I wish to know how many
> bytes a NxN matrix with real entries is, the list of its eigenvectors,
> eigenvalues etc.
>
> I know of the command "ByteCount", but the results I get are not
> consistent, i.e. a list of 1 integers does not take up the same amount
> of memory as one single integer etc. So: Is there a way to estimate
> these things? I'm running on a 32-bit system (if that makes a
> difference).



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