Re: GNAT compiler switches and optimization

[Warner BRUNS <Warner.Bruns@cern.ch>]

Georg Bauhaus wrote:
> On Mon, 2006-10-23 at 14:40 +0200, Warner BRUNS wrote:
> 
> 
>> A problem with Ada is that the memory layout of multidimensional arrays
>> is not specified in the standard. If you want to have the same memory
>> layout for all Ada compilers, you have to specify that a multimensional
>> array should follow the convention of a foreign language, eg. Fortran.
> 
> Will a memory layout cast in source really help with e.g. all
> Ada X Fortran combinations of compilers and libraries?
> It might disallow "knowledgeable" compilers to choose a layout
> that suits the current setup, I'd think, and require touching
> the sources.
> 
> 
> -- Georg 
> 
>
It will help with all Ada/ Fortran Compiler combinations,
but the really strange thing is that the memory layout is not
definitely known from the Ada source alone, if it is not specified
as being the layout as required by a different language, eg. Fortran.
    If one wants to code a cache aware algorithm for eg. multiplying
matrices, one cannot do this in Ada without enforcing the memory
layout of the matrices via PRAGMA CONVENTION.

Warner