[mpich-discuss] stdin redirection

Filippone, Salvatore Salvatore.Filippone at cranfield.ac.uk
Wed Jun 1 04:37:51 CDT 2016

I have found something I do not understand with mpich 3.2.0. The
problem started with an application, but to demonstrate it I have
written a very simple-minded program which I am including here. 
The program simply reads lines from standard input  and reprints them
on standard output from a second process. 

Now if I redirect stdin from a small(ish) file it works as expected:
[sfilippo at localhost MPI_cat]$ mpicc -v
mpicc for MPICH version 3.2
Using built-in specs.
Target: x86_64-unknown-linux-gnu
Configured with: ../gcc-5.3.0/configure --prefix=/opt/gnu/5.3.0 --
enable-languages=c,c++,fortran --with-
gmp=/usr/local/travel/GCC/BUILDS/gmp --with-
mpfr=/usr/local/travel/GCC/BUILDS/mpfr --with-
mpc=/usr/local/travel/GCC/BUILDS/mpc --with-
Thread model: posix
gcc version 5.3.0 (GCC) 
[sfilippo at localhost MPI_cat]$ mpicc -o mpicat mpicat.c
[sfilippo at localhost MPI_cat]$ head mpicat.c | mpirun -np 2 ./mpicat
#include <stdlib.h>
#include <stdio.h>
#include "mpi.h"
#define LNSZ  129
#define TAGI  234
#define TAGC  567
int main(int argc, char *argv[] )
  char linebuf[LNSZ];
  int ierr, iam, np, itmp ;
[sfilippo at localhost MPI_cat]$ 
However if I use a long(ish) file (such as a configure script) I get
either no output or an error. On another machine with GNU 4.9.3 I
always get the silent failure.
[sfilippo at localhost MPI_cat]$ mpirun -np 2 ./mpicat < configure 
[sfilippo at localhost MPI_cat]$ mpirun -np 2 ./mpicat < configure 
[proxy:0:0 at localhost.localdomain] HYD_pmcd_pmip_control_cmd_cb
(../../../../mpich-3.2/src/pm/hydra/pm/pmiserv/pmip_cb.c:937): process
reading stdin too slowly; can't keep up
[proxy:0:0 at localhost.localdomain] HYDT_dmxu_poll_wait_for_event
callback returned error status
[proxy:0:0 at localhost.localdomain] main (../../../../mpich-
3.2/src/pm/hydra/pm/pmiserv/pmip.c:206): demux engine error waiting for
[sfilippo at localhost MPI_cat]$ 

Am I missing something? 
Is this supposed to work? I could find nothing relevant in the FAQ

Thanks a lot 
Salvatore Filippone, PhD
Centre for Computational Engineering Sciences,
School of Aerospace, Transport and Manufacturing, Bldg 52
Cranfield University
MK43 0AL
United Kingdom
tel: +44(0) 1234 758361

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