Re: alternate simplified proposal #1 (fwd)

Leslie Hart NOAA/FSL ( hart@nipmuc.fsl.noaa.gov)
Tue, 11 Jun 96 13:11:48 BST

I think the utility functions will simplify things for
both Fortran and C users (I think especially Fortran). I
generally like the idea, but I would prefer to see it cast
as a putenv/getenv style.

MPI_Info_put (INOUT InfoHandle, IN ElementName, IN ElementValue)
MPI_Info_get (INOUT InfoHandle, IN ElementName, OUT ElementValue, OUT Flag)

C Bindings:
MPI_Info_create(MPI_Info *)
MPI_Info_put(MPI_Info, char *, char *)
MPI_Info_get(MPI_Info, char *, char *, int *)
MPI_Info_dup(MPI_Info, MPI_Info *)
MPI_Info_delete(MPI_Info *)

I think some things like this showed up in the dynamic chapter,
but were not expressed like getenv/putenv.

Leslie

With this approach I can imagine intercepting the IO calls (eg MPI_Open,
MPI_Read, ... (whatever names we choose)) using the profiling interface.
When in open I can inspect the info argument (using MPI_Info_get) for a
special indicator to use my protocol. If I find an indicator for my protocol,
I cache something in the file handle (or comm or whatever we decide represents
a file), if I don't find something I call PMPI_Open. My $0.02

So, does this belong in misc??

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I agree that some unification here would be very nice. For example, we now have
a new interface for building INFO handles when we want to spawn, and we have
just decided that these should be constructed out of {key,value} strings. But
we have no such interface for building the cmd line arrays, which is a real
wart. All of this nonsense is only needed because we care about FORTRAN
strings, so that's probably the right abstraction to use, I think. So how about
the following:

MPI_String_create(MPI_String *)
MPI_String_append(MPI_String *, char *)
MPI_String_dup(MPI_String, MPI_String *)
MPI_String_delete(MPI_String *)

This would allow us to build both key/val pairs and command lines, since we can
just pass "key=val" strings where appropriate.

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