Re: [Vxl-users] Matrix Alloc - how to check

[Ian S. <sc...@im...>]

There is a bug in the code causing this problem
vnl_c_vector_alloc() takes int types, so we are getting overflow. (On my 
64-bit windows box anyway)

111322800*7=1.45 * 2^29 elements
1.45 * 2^29  * sizeof(double) > 2^31

This looks like it the first hard requirement for large vnl_matricies.

I'll have a look into fixing vnl_c_vector_alloc, but it looks like this 
should really be fixed as part of a larger int->vcl_size_t fix for all 
vnl and vil.

Followups to vxl-maintainers only please.

Ian.






On 11/01/2011 20:18, Martin Reuter wrote:
> Hi,
>
> I reported a bug about the matrix alloc (a year or more ago). Just
> looked at the svn dev version and it still seems not to be fixed.
>
> The problem is:
> I try to alloc a large matrix, say:
>
>      vnl_matrix<double>  A( 111322800,7 );
>
> very likely the constructor will not get this much memory, but does not
> complain.
> Now I expect at least:
>      A.assert_size(111322800,7);
> to fail, but it does not.
>
> (It would be nice to have a better way of checking if the alloc went OK
> w/o exiting, maybe there is??)
>
> now if I do:
>     A[111322799][6] = 3.0;
>      vcl_cout<<  " success 111322799-6\n";
>
> I get a segfault.
>
> This should be fixed by:
> 1. having assert_size work as expected and not give OK, if the matrix
> could not allocate the mem
> 2. have a way of checking if allocation worked w/o exiting
>
> And if you are at it,
> it would be great if we had a :
>
> set_diagonal( const vnl_vector<  T>  &)
>
> and
>
> vnl_vector<  T>  get_diagonal()
>
> I need that quite often.
>
> Cheers, Martin
>
>
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