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Re: CRAY-style vector functions in AltiVec?

Does the vectorizer handle complex arithmetic originally written for the
Cray?

JT Nelson

----- Original Message -----
From: "Craig Hunter" <email@hidden>
To: <email@hidden>
Sent: Saturday, June 05, 2004 7:39 AM
Subject: Re: CRAY-style vector functions in AltiVec?


> > Message: 1
> > Date: Fri, 4 Jun 2004 15:23:36 +0100
> > Subject: CRAY-style vector functions in AltiVec?
> > Cc: Marc Balcells <email@hidden>
> > To: email@hidden
> > From: Marc Balcells <email@hidden>
> >
> > 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.
>
> Marc, this is an ongoing "reality" with mixing FORTRAN and C (or even
> different FORTRAN compilers). Sometimes you need to use flags to force
> underscore, case, and other naming conventions to be compatible. So don't
> worry about it, there should be a compiler flag to make everything
> compatible with your particular mix of compilers.
>
> > My question is, does vecLib or AltiVec have all the functions the
> > treecode calls? The code is Hernquist's (1990) fortran version of the
> > Barnes-Hut (1996) treecode, which Hernquist vectorized for the CRAY by
> > calling a number of CRAY vector functions. The functions and
> > subroutines are listed below, in f77.
>
> As far as I know, the answer is "no". This would have to be something you
> build yourself. Or, you could potentially use VAST to compile
pre-existing
> library code. I have found that VAST does a pretty good job taking code
> originally written for CRAY (where the CRAY compiler would auto-vecotrize)
> and vectorizing it for AltiVec instead. This may be something you want to
> discuss with the VAST guys (www.crescentbaysoftware.com) before going any
> further. They have a lot of expertise in this area.
>
> BTW, VAST works well with IBM XLF and the NAG compiler in addition to the
> Absoft compiler.
>
> Craig
>
>
> --
> Dr. Craig A. Hunter
> NASA Langley Research Center
> AAAC / Configuration Aerodynamics Branch
> (757) 864-3020
> email@hidden (NEW!!)
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References: 
 >Re: CRAY-style vector functions in AltiVec? (From: Craig Hunter <email@hidden>)



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