vitalif
/
mdtest
1
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

Improve scalability of CountTasksPerNode(). 

Improve the scalabilit of CountTasksPerNode() by using
a Broadcast and AllReduce, rather than flooding task zero
with MPI_Send() messages.

Also change the hostname lookup function from MPI_Get_processor_name
to gethostname(), which should work on most systems that I know of,
including BlueGene/Q.
master
Christopher J. Morrone 2012-09-12 11:21:41 -07:00
parent 84264657fb
commit 86df5878f6
1 changed files with 46 additions and 29 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

75
src/ior.c
View File

@ -449,46 +449,63 @@ static int CountErrors(IOR_param_t * test, int access, int errors)
} }
/* /*
* Compares hostnames to determine the number of tasks per node * Count the number of tasks that share a host.
*
* This function employees the gethostname() call, rather than using
* MPI_Get_processor_name(). We are interested in knowing the number
* of tasks that share a file system client (I/O node, compute node,
* whatever that may be). However on machines like BlueGene/Q,
* MPI_Get_processor_name() uniquely identifies a cpu in a compute node,
* not the node where the I/O is function shipped to. gethostname()
* is assumed to identify the shared filesystem client in more situations.
*
* NOTE: This also assumes that the task count on all nodes is equal
* to the task count on the host running MPI task 0.
*/ */
static int CountTasksPerNode(int numTasks, MPI_Comm comm) static int CountTasksPerNode(int numTasks, MPI_Comm comm)
{ {
char localhost[MAX_STR], hostname[MAX_STR], taskOnNode[MAX_STR]; char localhost[MAX_STR];
int count = 1, resultsLen = MAX_STR, i; char hostname0[MAX_STR];
static int firstPass = TRUE; static int firstPass = TRUE;
MPI_Status status; unsigned count;
unsigned flag;
MPI_CHECK(MPI_Get_processor_name(localhost, &resultsLen), int rc;
"cannot get processor name");
if (verbose >= VERBOSE_2 && firstPass) { if (verbose >= VERBOSE_2 && firstPass) {
sprintf(taskOnNode, "task %d on %s", rank, localhost); char tmp[MAX_STR];
OutputToRoot(numTasks, comm, taskOnNode); sprintf(tmp, "task %d on %s", rank, localhost);
OutputToRoot(numTasks, comm, tmp);
firstPass = FALSE; firstPass = FALSE;
} }
if (numTasks > 1) { rc = gethostname(localhost, MAX_STR);
if (rank == 0) { if (rc == -1) {
/* MPI_receive all hostnames, and compare to local hostname */ /* This node won't match task 0's hostname...expect in the
for (i = 0; i < numTasks - 1; i++) { case where ALL gethostname() calls fail, in which
MPI_CHECK(MPI_Recv case ALL nodes will appear to be on the same node.
(hostname, MAX_STR, MPI_CHAR, We'll handle that later. */
MPI_ANY_SOURCE, MPI_ANY_TAG, comm, localhost[0] = '\0';
&status), if (rank == 0)
"cannot receive hostnames"); perror("gethostname() failed");
if (strcmp(hostname, localhost) == 0)
count++;
}
} else {
/* MPI_send hostname to root node */
MPI_CHECK(MPI_Send(localhost, MAX_STR, MPI_CHAR, 0, 0,
comm), "cannot send hostname");
}
MPI_CHECK(MPI_Bcast(&count, 1, MPI_INT, 0, comm),
"cannot broadcast tasks-per-node value");
} }
return (count); /* send task 0's hostname to all tasks */
if (rank == 0)
strcpy(hostname0, localhost);
MPI_CHECK(MPI_Bcast(hostname0, MAX_STR, MPI_CHAR, 0, comm),
"broadcast of task 0's hostname failed");
if (strcmp(hostname0, localhost) == 0)
flag = 1;
else
flag = 0;
/* count the tasks share the same host as task 0 */
MPI_Allreduce(&flag, &count, 1, MPI_UNSIGNED, MPI_SUM, comm);
if (hostname0[0] == '\0')
count = 1;
return (int)count;
} }
/* /*