smp test: memset benchmarkHEADmasterlinaro_android

If all goes well, it prints some benchmark results (libc memset vs.
simple memset vs. parallelized simple memset vs. double-parallelized
simple memset) and exits with exit status 0.

If it doesn't go well, it tells what went wrong on stderr and exits
with a non-zero exit status.

Note that you'll also get a non-zero exit status if you run it on a
single-core box when all goes well -- since it's an SMP test, it
considers running things in a single thread an error (e.g. multiple
cores not being detected, e.g. because CONFIG_SMP is disabled in the
kernel).

1 files changed, 127 insertions, 0 deletions

diff --git a/smp.c b/smp.c
new file mode 100644
index 0000000..9d4ab9d
--- /dev/null
+++ b/smp.c
@@ -0,0 +1,127 @@
+#include <omp.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/time.h>
+
+void *simple_memset(void *s, int c, size_t n) {
+	char *m=(char*)s;
+	for(int i=0; i<n; i++)
+		m[i]=c;
+	return s;
+}
+
+void *parallel_memset(void *s, int c, size_t n) {
+	char *m=(char*)s;
+	#pragma omp parallel for
+	for(int i=0; i<n; i++)
+		m[i]=c;
+	return s;
+}
+
+int main(int argc, char **argv) {
+	static int threads=0;
+	static int ret=0;
+	#pragma omp parallel shared(threads) num_threads(3)
+	{
+		int thread = omp_get_thread_num();
+		#pragma omp barrier
+		if(thread == 0)
+			threads = omp_get_num_threads();
+	}
+	printf("Number of threads (3 requested): %u\n", threads);
+	if(threads != 3) {
+		fprintf(stderr, "Wrong number of threads (3 requested manually): %u\n", threads);
+		ret++;
+	}
+
+	#pragma omp parallel shared(threads)
+	{
+		int thread = omp_get_thread_num();
+		#pragma omp barrier
+		if(thread == 0)
+			threads = omp_get_num_threads();
+	}
+	printf("OpenMP wants to use %u threads\n", threads);
+	if(threads<2) {
+		fputs("OpenMP doesn't want to multi-thread.\nIf you aren't on a single-core machine, this is an SMP error.\n", stderr);
+		ret++;
+	}
+
+	char pattern[100000];
+	memset(pattern, 170 /* 10101010 */, 100000);
+
+	char *s=(char*)malloc(100000);
+	memset(s, 0, 100000);
+	struct timeval start, end;
+	double start_, end_;
+	gettimeofday(&start, 0);
+	for(int i=0; i<100000; i++) {
+		memset(s, 170 /* 10101010 */, 100000);
+		if(memcmp(s, pattern, 100000)) {
+			fputs("Incorrect result from memset", stderr);
+			ret++;
+			break;
+		}
+	}
+	gettimeofday(&end, 0);
+	start_ = start.tv_sec + (double)start.tv_usec/1000000.0;
+	end_ = end.tv_sec + (double)end.tv_usec/1000000.0;
+	printf("libc memset: %f\n", end_-start_);
+
+	memset(s, 0, 100000);
+	gettimeofday(&start, 0);
+	for(int i=0; i<100000; i++) {
+		simple_memset(s, 170, 100000);
+		if(memcmp(s, pattern, 100000)) {
+			fputs("Incorrect result from simple_memset", stderr);
+			ret++;
+			break;
+		}
+	}
+	gettimeofday(&end, 0);
+	start_ = start.tv_sec + (double)start.tv_usec/1000000.0;
+	end_ = end.tv_sec + (double)end.tv_usec/1000000.0;
+	double simple = end_-start_;
+	printf("simple memset: %f\n", simple);
+
+	memset(s, 0, 100000);
+	gettimeofday(&start, 0);
+	for(int i=0; i<100000; i++) {
+		parallel_memset(s, 170, 100000);
+		if(memcmp(s, pattern, 100000)) {
+			fputs("Incorrect result from parallel_memset", stderr);
+			ret++;
+			break;
+		}
+	}
+	gettimeofday(&end, 0);
+	start_ = start.tv_sec + (double)start.tv_usec/1000000.0;
+	end_ = end.tv_sec + (double)end.tv_usec/1000000.0;
+	double parallel = end_-start_;
+	printf("parallel memset: %f\n", parallel);
+
+	memset(s, 0, 100000);
+	gettimeofday(&start, 0);
+	#pragma omp parallel for
+	for(int i=0; i<100000; i++) {
+		parallel_memset(s, 170, 100000);
+		if(memcmp(s, pattern, 100000)) {
+			fputs("Incorrect result from parallel_memset", stderr);
+			ret++;
+		}
+	}
+	gettimeofday(&end, 0);
+	start_ = start.tv_sec + (double)start.tv_usec/1000000.0;
+	end_ = end.tv_sec + (double)end.tv_usec/1000000.0;
+	printf("double-parallel memset: %f\n", parallel);
+
+	free(s);
+
+	if(parallel>simple && threads >= 2) {
+		fputs("Parallel memset slower than simple memset even though multiple\nthreads are enabled. This is an indication of a possible SMP error.\n", stderr);
+		ret++;
+	}
+
+	return ret;
+}