[gomp] New tasking testcase/benchmark

[Jakub Jelinek <jakub at redhat dot com>]

Hi!

Just a classical tasking example, which can serve both as a testcase
and a benchmark (in that case with bigger N than 8, like 14 or 15).
Committed to trunk.

2008-06-19  Jakub Jelinek  <jakub@redhat.com>

	* testsuite/libgomp.c/nqueens-1.c: New test.

--- libgomp/testsuite/libgomp.c/nqueens-1.c	(revision 0)
+++ libgomp/testsuite/libgomp.c/nqueens-1.c	(revision 136942)
@@ -0,0 +1,66 @@
+/* { dg-do run } */
+/* { dg-options "-O2 -fopenmp" } */
+/* { dg-require-effective-target tls_runtime } */
+
+#include <omp.h>
+#include <stdio.h>
+#include <string.h>
+
+int cnt;
+#pragma omp threadprivate (cnt)
+
+void
+nqueens (char *a, int n, int pos)
+{
+  /* b[i] = j means the queen in i-th row is in column j.  */
+  char b[pos + 1];
+  int i, j;
+  memcpy (b, a, pos);
+  for (i = 0; i < n; i++)
+    {
+      for (j = 0; j < pos; j++)
+	if (b[j] == i || b[j] == i + pos - j || i == b[j] + pos - j)
+	  break;
+      if (j < pos)
+	continue;
+      if (pos == n - 1)
+	/* Found a solution.  Could output it here.  */
+	++cnt;
+      else
+	{
+	  b[pos] = i;
+	  #pragma omp task
+	    nqueens (b, n, pos + 1);
+	}
+    }
+}
+
+int
+main (int argc, char **argv)
+{
+  int n = 8;
+  if (argc >= 2)
+    n = strtoul (argv[1], NULL, 0);
+  if (n < 1 || n > 127)
+    {
+      fprintf (stderr, "invalid count %d\n", n);
+      return 1;
+    }
+  cnt = 0;
+  double stime = omp_get_wtime ();
+  nqueens ("", n, 0);
+  printf ("serial   N %d solutions # %d time %f\n", n, cnt, omp_get_wtime () - stime);
+  #pragma omp parallel
+    cnt = 0;
+  stime = omp_get_wtime ();
+  int tempcnt = 0;
+  #pragma omp parallel reduction (+:tempcnt)
+    {
+      #pragma omp single
+	nqueens ("", n, 0);
+      tempcnt = cnt;
+    }
+  cnt = tempcnt;
+  printf ("parallel N %d solutions # %d time %f\n", n, cnt, omp_get_wtime () - stime);
+  return 0;
+}

	Jakub