Changes between Version 14 and Version 15 of Challenge

Timestamp:

03/12/19 11:23:41 (7 years ago)

Author:

siegel

Comment:

--

Challenge

@@ -146 +146 @@
 concurrently in separate threads.  Used to avoid deadlocks that could
 result if all processes do `MPI_Send; MPI_Recv`.
+
+
+== A two-thread barrier using semaphores in CIVL-C ==
+
+{{{
+#include <stdio.h>
+
+int s1=0, s2=0;
+#define sem_wait(s) $when (s>0) s--;
+#define sem_post(s) s++;
+const int N=10;
+int i1=0, i2=0;
+
+void f1() {
+  while (i1<N) {
+    printf("thread 1 at iteration %d\n", i1);
+    fflush(stdout);
+    i1++;
+    sem_post(s1);
+    sem_wait(s2);
+    $assert(i1==i2);
+    sem_post(s1);
+    sem_wait(s2);
+  }
+}
+
+void f2() {
+  while (i2<N) {
+    printf("thread 2 at iteration %d\n", i2);
+    fflush(stdout);
+    i2++;
+    sem_post(s2);
+    sem_wait(s1);
+    $assert(i1==i2);
+    sem_post(s2);
+    sem_wait(s1);
+  }
+}
+
+int main() {
+  $proc t1 = $spawn f1(), t2 = $spawn f2();
+  $wait(t1);
+  $wait(t2);
+}
+}}}