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Re: CRAY-style vector functions in AltiVec?

On 4-jun-04, at 16:23, Marc Balcells wrote:

Hello,

I have compiled a f77 gravitational N-body tree-code on my PBook G4 (OSX10.2.8, g77), and its performance is not great - similar to the same code running on a Sun ultra5. I have found plenty documentation about the G4 only being competitive for HPC when using AltiVec, which makes sense, and learned the basics of writing C wrapper functions to allow a call to altivec from fortran. This was tricky with g77 but managed to make it work using an example given in a useful posting by Craig Hunter (fortran lists, April 2002). BTW I noted a nasty feature, subroutine names with underscores within the name do not seem to be acceptable - the linker does not find the corresponding C functions.

I have been doing some Fortran wrapping myself the last couple of days. And this is what I noticed:
g77 adds an additional '_' to the end if your identifier contains any '_' of itself. So if you add an additional '_' to your wrapped C function it should work (e.g. use foo_bar__ instead of foo_bar_ to wrap the function foo_bar).

Best regards,
Sander Niemeijer
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References: 
 >CRAY-style vector functions in AltiVec? (From: Marc Balcells <email@hidden>)



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