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From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Re: Interfacing Ada multidimensional arrays with Fortran.
Date: Sat, 28 May 2011 17:45:59 +0100
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Date: 2011-05-28T17:45:59+01:00
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Simon Wright <simon@pushface.org> writes:

>> What are the performance issues by using the three possibilities
>> above ? (may be the community already had some interesting information
>> about this)
>
> I haven't measured this. Anyone else?

On Mac OS X, using GCC 4.6.0, with -O1, applying
System.Generic_Array_Operations.Transpose 10 times to a 100x100 matrix
took 900 us, whereas using assignment with convention Fortran took 90
us.

With -O2, the assignment was hoisted out of the loop.

I then made the target matrices volatile; the results are now

-O1:
Transposition: 1200 us
Assignment:     300 us

-O2:
Transposition:  500 us
Assignment:     300 us