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From: Niklas Holsti <niklas.holsti@tidorum.invalid>
Newsgroups: comp.lang.ada
Subject: Re: ada lapack
Date: Sun, 19 Aug 2012 02:16:06 +0300
Organization: Tidorum Ltd
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Date: 2012-08-19T02:16:06+03:00
List-Id: <comp.lang.ada>

On 12-08-19 01:51 , Nasser M. Abbasi wrote:
> On 8/18/2012 3:45 PM, Niklas Holsti wrote:
> 
>>
>> I wonder why Ada_Lapack needs convention-Fortran matrices, when it does
>> not use any Fortran code.
> 
> I assumed all along this is becuase Fortran matrix is column major
> order for storing the memory layout for the matrix. C uses row
> major, and I assumed Ada does also. Fortran and Matlab uses Column
> major.

All true (well, I don't know about Matlab, but I can believe you).

If Ada code passes matrices to Fortran code, the Fortran layout must be
used, since the Fortran code assumes it. (Or else the Fortran code sees
the matrix as transposed.)

But the layout of a matrix in pure Ada code does not matter (except,
possibly, for execution time) if the code accesses the matrix in the
usual way with indices. The layout matters only if the matrix is
accessed in some nasty way, such as by using overlays (for X'address use
...) as is now done in Ada_Lapack.

-- 
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
      .      @       .