Overcome matrix maximum size problem

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Talaria 2011-8-7

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how could i possibly overcome the problem of being limited by matrix maximum size. i am thinking of maybe storing values to a file? is this possible?

suppose i have a code that lists a matrix of all binary possibilities from 0 to n, if n is too great the matrix would not be enough to store all values. what would be a good solution? also considering RAM limitations.

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Answer 1

Jan 2011-8-7

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Accessing the harddisk is about 1000 times slower than RAM access. And if the calculation of the permutations of more than 52 symbols (from your last post) takes some years, writing this to the disk will exceed the life time of the computer in every case.

The solution is easy: Do not do this. There is simply no reason to calculate a giantic array which such a tiny density of information. It will be more efficient to create the single lines (or rows) dynamically. For permutations this can be done e.,g. by:

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Walter Roberson 2011-8-7

I believe you misread the previous posting. It wasn't about permutations, it was about finding all the binary strings of a certain length, n, n > 53

Jan 2011-8-7

@walter: You are right. The binary string problem is not a "permutation", but a "combination with repetitions". I spend much time to implement the 4 very efficient VChooseK(R)(O) as C-Mex in the FEX, but I still confuse the terms.

Thanks, Walter. As usual it is helpful to know, that you catch errors!

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