[petsc-users] Problem with MPI_Allreduce

[Praveen C]

Dear all

I use MPI_Allreduce in my petsc code and when compiling I see this type of messages

/home/soft/include/petsclog.h:376:57: warning: value computed is not used [-Wunused-value]
   ((petsc_allreduce_ct += PetscMPIParallelComm(comm),0) || MPI_Allreduce(sendbuf,recvbuf,count,datatype,op,comm))
                                                         ^
fdweno.c:564:4: note: in expansion of macro ‘MPI_Allreduce’
    MPI_Allreduce(&lamx, &lambdax, 1, MPI_DOUBLE, MPI_MAX, PETSC_COMM_WORLD);
    ^~~~~~~~~~~~~

This is with petsc-3.8.3 on Linux. 

My code crashes due to this error I think, while I dont get this problem on my macbook which uses petsc-3.9.0

Since the error is pointing to petsclog.h I thought I will ask here.

Thanks
praveen