[mpich-commits] [mpich] MPICH primary repository branch, master, updated. v3.1rc2-165-g4e1b470
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http://git.mpich.org/mpich.git/commitdiff/4e1b470dd1b47b514c65da9add3613fdd301c90c
commit 4e1b470dd1b47b514c65da9add3613fdd301c90c
Author: William Gropp <wgropp at illinois.edu>
Date: Thu Jan 16 15:29:32 2014 -0600
Fix bogus datatype perf test
The test in test/mpi/perf/twovec made invalid assumptions about the
performance of two MPI datatype creation routines. This is a hard test to
get right, but this version is more likely to avoid falsely signalling
an error.
diff --git a/test/mpi/perf/twovec.c b/test/mpi/perf/twovec.c
index 1bbe5a3..774693e 100644
--- a/test/mpi/perf/twovec.c
+++ b/test/mpi/perf/twovec.c
@@ -9,11 +9,20 @@
#include <math.h>
#include "mpi.h"
-/* Make sure datatype creation is independent of data size */
+/* Make sure datatype creation is independent of data size
+ Note, however, that there is no guarantee or expectation
+ that the time would be constant. In particular, some
+ optimizations might take more time than others.
+
+ The real goal of this is to ensure that the time to create
+ a datatype doesn't increase strongly with the number of elements
+ within the datatype, particularly for these datatypes that are
+ quite simple patterns.
+ */
#define SKIP 4
#define NUM_SIZES 16
-#define FRACTION 0.2
+#define FRACTION 1.0
/* Don't make the number of loops too high; we create so many
* datatypes before trying to free them */
@@ -23,14 +32,15 @@ int main(int argc, char *argv[])
{
MPI_Datatype column[LOOPS], xpose[LOOPS];
double t[NUM_SIZES], ttmp, tmin, tmax, tmean, tdiff;
+ double tMeanLower, tMeanHigher;
int size;
- int i, j, isMonotone, errs = 0, nrows, ncols, isvalid;
+ int i, j, errs = 0, nrows, ncols;
MPI_Init(&argc, &argv);
tmean = 0;
- size = 1;
- for (i = 0; i < NUM_SIZES + SKIP; i++) {
+ size = 1;
+ for (i = -SKIP; i < NUM_SIZES; i++) {
nrows = ncols = size;
ttmp = MPI_Wtime();
@@ -41,9 +51,15 @@ int main(int argc, char *argv[])
MPI_Type_commit(&xpose[j]);
}
- if (i >= SKIP) {
- t[i - SKIP] = MPI_Wtime() - ttmp;
- tmean += t[i - SKIP];
+ if (i >= 0) {
+ t[i] = MPI_Wtime() - ttmp;
+ if (t[i] < 100 * MPI_Wtick()) {
+ /* Time is too inaccurate to use. Set to zero.
+ Consider increasing the LOOPS value to make this
+ time large enough */
+ t[i] = 0;
+ }
+ tmean += t[i];
}
for (j = 0; j < LOOPS; j++) {
@@ -51,19 +67,37 @@ int main(int argc, char *argv[])
MPI_Type_free(&column[j]);
}
- if (i >= SKIP)
+ if (i >= 0)
size *= 2;
}
tmean /= NUM_SIZES;
- /* Now, analyze the times to see that they are nearly independent
- * of size */
- for (i = 0; i < NUM_SIZES; i++) {
- /* The difference between the value and the mean is more than
- * a "FRACTION" of mean. */
- if (fabs(t[i] - tmean) > (FRACTION * tmean))
- errs++;
- }
+ /* Now, analyze the times to see that they do not grow too fast
+ as a function of size. As that is a vague criteria, we do the
+ following as a simple test:
+ Compute the mean of the first half and the second half of the
+ data
+ Compare the two means
+ If the mean of the second half is more than FRACTION times the
+ mean of the first half, then the time may be growing too fast.
+ */
+ tMeanLower = tMeanHigher = 0;
+ for (i=0; i<NUM_SIZES/2; i++)
+ tMeanLower += t[i];
+ tMeanLower /= (NUM_SIZES/2);
+ for (i=NUM_SIZES/2; i<NUM_SIZES; i++)
+ tMeanHigher += t[i];
+ tMeanHigher /= (NUM_SIZES - NUM_SIZES/2);
+ /* A large value (even 1 or greater) is a good choice for
+ FRACTION here - the goal is to detect significant growth in
+ execution time as the size increases, and there is no MPI
+ standard requirement here to meet.
+
+ If the times were too small, then the test also passes - the
+ goal is to find implementation problems that lead to excessive
+ time in these routines.
+ */
+ if (tMeanLower > 0 && tMeanHigher > (1 + FRACTION) * tMeanLower) errs++;
if (errs) {
fprintf(stderr, "too much difference in performance: ");
-----------------------------------------------------------------------
Summary of changes:
test/mpi/perf/twovec.c | 68 ++++++++++++++++++++++++++++++++++++------------
1 files changed, 51 insertions(+), 17 deletions(-)
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