Merge branch 'master' of github.com:lnslbrty/foo-scripts

1 files changed, 68 insertions, 0 deletions

diff --git a/parallel/nosync.c b/parallel/nosync.c
new file mode 100644
index 0000000..9ddc5a3
--- /dev/null
+++ b/parallel/nosync.c
@@ -0,0 +1,68 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include <pthread.h>
+
+#include <assert.h>
+
+
+struct thread_data {
+  pthread_t thrd;
+  int id;
+  int result;
+};
+  
+
+#define NTHREADS 8
+static const unsigned int nthreads = NTHREADS;
+static const unsigned int iterations = 4000;
+static struct thread_data thrds[NTHREADS];
+
+/* r/w by threads */
+static int sum = 0;
+
+
+void *
+thread_func(void *arg)
+{
+  int i;
+  int s;
+  struct thread_data *td = (struct thread_data *) arg;
+
+  printf("Thread %d started ..\n", td->id);
+
+  /* critical section - no sync */
+  s = sum; // READ
+  for (i = 0; i < iterations; i++) {
+    s++;
+  }
+  sum = s; // WRITE
+
+  return NULL;
+}
+
+int
+main(int argc, char *argv[])
+{
+  int i;
+
+  for (i = 0; i < nthreads; i++) {
+    thrds[i].id = i;
+    thrds[i].result = 0;
+    assert( pthread_create( &(thrds[i].thrd), NULL, thread_func, (void*)&thrds[i] ) == 0 );
+  }
+
+  for (i = 0; i < nthreads; i++) {
+    assert( pthread_join(thrds[i].thrd, NULL) == 0 );
+  }
+
+  printf("Expected result: sum == %d\n", iterations*nthreads);
+  if (sum == iterations*nthreads) {
+    printf("It worked randomly, lucky dude ..\n");
+  } else {
+    printf("This should be the common occasion: sum == %d\n", sum);
+  }
+
+  return 0;
+}