MPIX_Comm_failure_ack(3)

💖 MPIX_Comm_failure_ack — NAME 💖

okay so bestie, this is the MPIX_Comm_failure_ack(3) page from the MPI manual (section 3), and it's literally all about one thing: acknowledging the current group of failed processes. That's the vibe. Periodt. 💅

✨ SYNOPSIS ✨

int MPIX_Comm_failure_ack(MPI_Comm comm)

🫶 INPUT PARAMETERS 🫶

• comm — communicator (handle). That's it. That's the whole input, bestie.

💅 NOTES 💅

This is a local operation, which means it gives users a way to acknowledge all locally notified failures on comm. Like, "yeah bestie, I see the failures, I'm acknowledging them." Iconic.

After the call, unmatched MPI_ANY_SOURCE receive operations that would have raised an error of class MPI_ERR_PROC_FAILED_PENDING due to MPI process failure proceed without further raising errors due to those acknowledged failures. No cap.

Also after this call, MPIX_Comm_agree will not raise an error of class MPI_ERR_PROC_FAILED due to those acknowledged failures. Slay. ✨

🧚 THREAD AND INTERRUPT SAFETY 🧚

This routine is thread-safe. This means that this routine may be safely used by multiple threads without the need for any user-provided thread locks. We love that for us. 🫶

However — and this is the important part — the routine is not interrupt safe. Typically, this is due to the use of memory allocation routines such as malloc or other non-MPICH runtime routines that are themselves not interrupt-safe. So like, thread-safe yes, interrupt-safe no. Vibe check passed for threads, failed for interrupts. 💀

🌈 NOTES FOR FORTRAN 🌈

All MPI routines in Fortran (except for MPI_WTIME and MPI_WTICK) have an additional argument ierr at the end of the argument list. ierr is an integer and has the same meaning as the return value of the routine in C.

In Fortran, MPI routines are subroutines, and they are invoked with the call statement.

All MPI objects (e.g., MPI_Datatype, MPI_Comm) are of type INTEGER in Fortran. Fortran said "handles? never heard of her, everything is INTEGER." 👑

😭 ERRORS 😭

All MPI routines (except MPI_Wtime and MPI_Wtick) return an error value; C routines as the value of the function and Fortran routines in the last argument. Before the value is returned, the current MPI error handler is called. By default, this error handler aborts the MPI job.

The error handler may be changed with MPI_Comm_set_errhandler (for communicators), MPI_File_set_errhandler (for files), and MPI_Win_set_errhandler (for RMA windows). The MPI-1 routine MPI_Errhandler_set may be used but its use is deprecated. The predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be returned.

Note that MPI does not guarantee that an MPI program can continue past an error; however, MPI implementations will attempt to continue whenever possible.

Here are the error codes, bestie:

• MPI_SUCCESS — No error; MPI routine completed successfully. We love a clean run. ✨
• MPI_ERR_COMM — Invalid communicator. A common error is to use a null communicator in a call (not even allowed in MPI_Comm_rank). So don't do that. 🙈
• MPI_ERR_OTHER — Other error; use MPI_Error_string to get more information about this error code.

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And that's the whole page! Sign-off time: this was the MPIX_Comm_failure_ack(3) manual page, dated 4/10/2026, from the MPI manual. Go acknowledge those failures, bestie, you got this. 💜🦋