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1.2 Current Parallel Programming Paradigms - page 26 / 33

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MESSAGE MODES

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M P I _ C O M M _ W O R gen. count 0 L

recovery procedure

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Figure 5.1: Example for a message sent and received in the same communi- cator however with di erent generation counts

Imagine for example the case, that process a posts a non-blocking receive operation from process b. Process b fails, before the data transmission can be finished. If the receive operation has been posted using a specified sender, the MPI-library can ’cancel’ this operation and declare the request to be invalid. However, if the receive operation has been posted using MPI ANY- SOURCE and no other process is sending a message which can match the posted receive, the application will deadlock.

Advice

to

users

The

usage

of

MPI

ANY

SOURCE

should

be

avoided to the greates possible extent mode FTMPI MSG MODE CONT.

when

using

the

message

For discussion

A possibility would be to give the user an at-

tribute after the recovery handles which the system

operation, which contains all request- could not dissolve, especially the ones

which have been posted using MPI

ANY

SOURCE. It is than the

responsibility of the user communication continue.

to

either

cancel

the

request

or

let

the

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