(j3.2006) (SC22WG5.3880) [ukfortran] [MPI3 Fortran] MPI non-blocking transfers

Aleksandar Donev donev1
Wed Jan 21 19:17:53 EST 2009


On Wednesday 21 January 2009 16:04, Van Snyder wrote:

> or is there another cause for it?
YES!!! Why do we have the ASYNCHRONOUS attribute instead of just having 
WAIT?!? The compiler must know that a variable can change behind its 
back, must now not to perform copy in/out and "optimizations", and the 
standard has several restrictions on ASYNCHRONOUS dummies (see chapter 
12). These are all "other causes" and have no connection to WAIT what 
so ever.

And no, this is not a defect with MPI's interface. It is simply another 
way to do interfaces. Plenty of libraries save pointers and do not ask 
you to pass the same 100 arguments both for the "start" and the "end" 
of an operation. It is perfectly sensible design, especially in the C 
world.

Best,
Aleks



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