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<p>Some MPI implementations have added new, predefined datatypes that are not in the MPI Standard. These are the the MIN_LOC/MAX_LOC operands MPI_2COMPLEX and MPI_2DOUBLE_COMPLEX. There is now at least one widely used application that depends on MPI_2COMPLEX. That application does not port to any MPI which lacks the non-standard MPI_2COMPLEX type.<br>
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I do not recall any discussions about MPI_2COMPLEX but they probably did occur. Some people seem convinced MPI_2COMPLEX is part of MPI-2.0. I searched both 2.0 and 2.2 without finding them.<br>
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I think the ambiguity in the meaning of less_than / greater_than when applied to complex numbers would be a good reason to consider leaving the datatypes and the associated MIN_LOC & MAX_LOC operations out of any standard. The idea of returning a location in a complex number is sort of ugly too but well enough defined to be acceptable.<br>
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My understanding, going back to MPI 1.1 days, is that MPI implementations were to avoid inventing names with an MPI_ prefix so any name with that prefix could be used safely by follow-on MPI Fora that were extending the standard.<br>
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We do now have these MPI_ names among users and people are assuming the should be able to use them portably. I think the Forum needs to take a position and either add them to the standard (with a clear definition of MPI_LOC and MAX_LOC behavior) or deprecate them.<br>
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Dick <br>
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Dick Treumann - MPI Team <br>
IBM Systems & Technology Group<br>
Dept X2ZA / MS P963 -- 2455 South Road -- Poughkeepsie, NY 12601<br>
Tele (845) 433-7846 Fax (845) 433-8363<br>
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