Am 04.05.2009 um 16:53 schrieb Prentice Bisbal:
Chris Samuel wrote:
----- "Mike Davis" <jmdav...@vcu.edu> wrote:
Also, a particular code may run much better with
one "optimized" compiler than another. I have some
that require PGI to run at all.
This is one of our main reasons we maintain multiple
commercial compilers - letting our users easily build
code that is dependent on a specific compiler.
I suspect the cost of the compiler easily outweighs
the cost of our time to try and help them get it
working (if possible), not to mention the potential
opportunity "cost" to the researchers of them giving
up on HPC because they can't get it to work and it
doesn't occur to them to ask for help.
I second that. On more than one occasion, I spent weeks trying to get
code to compile using the compilers on hand before giving up and
spending $$ on a commercial compiler which compiled the code w/o any
problems.
In an ideal world, the code/Makefiles/configure scripts would written
such that any standards-compliant compiler would work, but that's not
always the case.
Another problem: some flag -xzy might be the option -abc with another
compiler. So, if a makefile assumes a certain compiler (and a certain
version of it), you will always have to lookup the corresponding
notation for another compiler, as the compiler developer is free to
introduce any new feature with a new option flag. I remember to use -
mp (now called -fp-model) for the Intel compiler, when it was -pc64
for Portland one. And this already means, that for the same compiler
the flags change over time.
And even if the code compiles with another compiler: you have to
validate the results, when the code was specified to be correct with
a certain compiler other than the used one.
-- Reuti
--
Prentice
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