Dear OpenMPI, using MPI_Allgather with MPI_CHAR type, I have a doubt about null-terminated character. Imaging I want to spawn node names where my program is running on:
---------------------------------------- char hostname[MAX_LEN]; char* hostname_recv_buf=(char*)calloc(num_procs*(MAX_STRING_LEN),(sizeof(char))); MPI_Allgather(hostname, MAX_STRING_LEN, MPI_CHAR, hostname_recv_buf, MAX_STRING_LEN, MPI_CHAR, MPI_COMM_WORLD); ---------------------------------------- Now, is the null-terminated character of each local string included? Or I have to send and receive in MPI_Allgather MAX_STRING_LEN+1 elements? Using Valgrind, in a subsequent simple strcmp: for( i= 0; i< num_procs; i++){ if(strcmp(&hostname_recv_buf[MAX_STRING_LEN*i], local_hostname)==0){ ... doing something.... } } raise a warning: Conditional jump or move depends on uninitialised value(s) ==19931== at 0x4A06E5C: strcmp (mc_replace_strmem.c:412) The same warning is not present if I use MAX_STRING_LEN+1 in MPI_Allgather. Thanks in forward. -- Ing. Gabriele Fatigati HPC specialist SuperComputing Applications and Innovation Department Via Magnanelli 6/3, Casalecchio di Reno (BO) Italy www.cineca.it Tel: +39 051 6171722 g.fatigati [AT] cineca.it