Re: Multi-array usage problem - Bug or me?

From: rgarcia1771 (garcia_at_[hidden])
Date: 2003-06-03 10:23:55

--- In Boost-Users_at_[hidden], "David Johnson"
<yg-boost-users_at_m...> wrote:
> I have the following code that I don't feel is doing the right
thing. Did I
> make some mistake or is the Multi-array code buggy?

There are several mistakes in this code snippet:

The ranges passed to the extents parameter are half open. This means
that the length of the range is the second number minus the first
number.  For example:
range(1,nrows) // where nrows = 2

specifies a range of 1 ( == nrows-1).  Your example is constructing an
array of shape 1 x 5.

To avoid this problem, I would probably rewrite your construction
sequence as the following:

B(extents[nrows][aSize]),fortran_storage_order());
B.reindex(1);

It also appears that you are indexing the array backwards. The lines
where you index as B[1][2] ... B[6][2]
should be B[2][1] ... B[2][6].

I suspect that these indices are reversed because you are interfacing
with fortran.  The fortran_storage_order parameter to the array makes
this reversal unnecessary.

Cheers,

ron

> typedef array_type::extent_range range;
> array_type
>
B(boost::extents[range(1,nrows)][range(1,aSize)],b
oost::fortran_storage_orde
> r());
> B[1][1] = 1.0;
> printf("\n first B11 %lf %lf %lf %lf %lf
> %lf",B[1][1],B[2][1],B[3][1],B[4][1],B[5][1],B[5][1]);
> printf("\n first B21 %lf %lf %lf %lf %lf
> %lf",B[1][2],B[2][2],B[3][2],B[4][2],B[5][2],B[6][2]);
> ...
>