Distributed Memory Checking


This feature is enabled by default if all processes run under Valgrind*. If that is not the case, it is disabled. If in doubt, check the configuration summary at the beginning of the run to see whether this feature was enabled or not. There are no Intel® Trace Collector error reports with this type; Valgrind's error reports have to be watched instead to find problems related to memory initialization. See the section "Use of uninitialized values" in Valgrind's user guide for details.

If enabled, then Valgrind's tracking of memory definedness is extended to the whole application. For applications which transmit partially initialized data between processes, this avoids two cases:

  • false positive: sending the message with the partially initialized data triggers a valgrind report for send or write system calls at the sender side

  • false negative: at the recipient, valgrind incorrectly assumes that all incoming data is completely initialized and thus will not warn if the uninitialized data influences the control flow in the recipient; normally it would report that

To handle the false positive case Valgrind must have been started with the suppression file provided with Intel® Trace Collector. The local/memory/valgrind example demonstrates both cases.

Turning this feature off is useful if the application is supposed to be written in such a way that it never transmits uninitialized data. In that case Intel® Trace Collector suppression file should not be used because it would suppress warnings at the sender and the LOCAL:MEMORY:ILLEGAL_ACCESS must be disabled as it would cause extra valgrind reports.

See Also

Running with Valgrind*

For more complete information about compiler optimizations, see our Optimization Notice.