[yt-users] curious warning message in parallelHOP

[Matthew Turk]

Hi Geoffrey,

Grepping through the yt codebase, I think the most likely culprit is
that get_memory_usage (which I believe gets called often during
parallel HOP) falls back on calling popen, which results in a fork.  I
think John might have added this.  I am -1 on this being default
behavior, and +1 on changing fallback (by default) to just return 0 if
it can't get memory information from the resource module, and maybe
governing this with a config parameter.  John, what do you think?

-MAtt

On Wed, May 9, 2012 at 7:46 PM, Geoffrey So <gsiisg at gmail.com> wrote:
> I got this warning message when running paralllel HOP, which I guess was
> there before but never noticed before because it's close to the top (usually
> looking at the bottom of the logs).  I was wondering if there's anything I
> need to worry about?
>
> --------------------------------------------------------------------------
> An MPI process has executed an operation involving a call to the
> "fork()" system call to create a child process.  Open MPI is currently
> operating in a condition that could result in memory corruption or
> other system errors; your MPI job may hang, crash, or produce silent
> data corruption.  The use of fork() (or system() or other calls that
> create child processes) is strongly discouraged.
>
> The process that invoked fork was:
>
>   Local host:          lens51 (PID 6818)
>   MPI_COMM_WORLD rank: 323
>
> If you are *absolutely sure* that your application will successfully
> and correctly survive a call to fork(), you may disable this warning
> by setting the mpi_warn_on_fork MCA parameter to 0.
> --------------------------------------------------------------------------
> [lens6:19012] 447 more processes have sent help message help-mpi-runtime.txt
> / mpi_init:warn-fork
> [lens6:19012] Set MCA parameter "orte_base_help_aggregate" to 0 to see all
> help / error messages
> [lens6:19012] 32 more processes have sent help message help-mpi-runtime.txt
> / mpi_init:warn-fork
> [lens6:19012] 32 more processes have sent help message help-mpi-runtime.txt
> / mpi_init:warn-fork
>
> From
> G.S.
>
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