Re: how to make a matrix with all combinations of digits efficiently

[Francesco Potortì]

>>>result=decomp(10,9);
>>>error: out of memory or dimension too large for Octave's index type
>>
>> decomp(B,C) creates a matrix with B^C rows and C columns.  In the case
>> you tested this means 9e9 elements.  Each element is a double needing 8
>> bytes, which means that you need 72GB of memory only for hosting the
>> final result.  In practice, you need additional space for hosting
>> intermediate variables.
>>
>I wonder whether it is possible to make octave  store the array more
>efficiently knowing that the elements are all
>integers which can be represented by 1 byte

Yes, you can, but reducing memory footprint is not so obvious, because
you should care about intermediate results.

>> This is the only problem if Octave has been specially compiled for using
>> 64-bit indexes, which is not the general case, and most probably not
>> your case.
>>
>> For the general case, have a look at
>> https://wiki.octave.org/Enable_large_arrays:_Build_octave_such_that_it_can_use_arrays_larger_than_2Gb.
>>
>Unfortunately this wiki-page is empty

Your mail client probably strips the last dot from the URL, try this
one:
<https://wiki.octave.org/Enable_large_arrays:_Build_octave_such_that_it_can_use_arrays_larger_than_2Gb.>

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