What should I make of the following warning, where I have used an MPI_Allreduce
on a quantity computed on each processor.
include -I/opt/local/include -I/opt/local/include/mpich-gcc48
-I/opt/local/include `pwd`/petsc_trapz1.c
In file included from /opt/local/lib/petsc/include/petscsys.h:1794:0,
from /opt/local/lib/petsc/include/petscis.h:7,
from /opt/local/lib/petsc/include/petscvec.h:9,
from /Users/gideon/code/trapz/petsc_trapz1.c:3:
/Users/gideon/code/trapz/petsc_trapz1.c: In function 'main':
/opt/local/lib/petsc/include/petsclog.h:370:57: warning: value computed is not
used [-Wunused-value]
((petsc_allreduce_ct += PetscMPIParallelComm(comm),0) ||
MPI_Allreduce(sendbuf,recvbuf,count,datatype,op,comm))
^
/Users/gideon/code/trapz/petsc_trapz1.c:110:3: note: in expansion of macro
'MPI_Allreduce'
MPI_Allreduce(&local_trapz, &global_trapz, 1, MPI_DOUBLE, MPI_SUM,
PETSC_COMM_WORLD);
-gideon
