[R] allocMatrix limits
Vadim Kutsyy
vadim at kutsyy.com
Fri Aug 1 16:35:01 CEST 2008
Martin Maechler wrote:
>
> VK> The problem is in array.c, where allocMatrix check for
> VK> "if ((double)nrow * (double)ncol > INT_MAX)". But why
> VK> itn is used and not long int for indexing? (max int is
> VK> 2147483647, max long int is 9223372036854775807)
>
> Well, Brian gave you all info:
>
exactly, and given that most modern system used for computations (i.e.
64bit system) have long int which is much larger than int, I am
wondering why long int is not used for indexing (I don't think that 4
bit vs 8 bit storage is an issue).
> Did you really carefully read ?Memory-limits
> ??
>
Yes, it is specify that 4 bit int is used for indexing in all version of
R, but why? I think 2147483647 elements for a single vector is OK, but
not as total number of elements for the matrix. I am running out of
indexing at mere 10% memory consumption.
> BTW: The package 'Matrix' has many facilities to work with
> sparse matrices;
Is is a very good package, but I don't see a relation to a limitation in
array.c (and I don't have scarce matrices).
Thanks,
Vadim
PS: I have no problem to go and modify C code, but I am just wondering
what are the reasons for having such limitation.
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