add cpu contention benchmarks

.gitignore

@@ -1 +1,2 @@
 *.out
+

contention.c

@@ -0,0 +1,60 @@
+#include <pthread.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <unistd.h>
+
+#include "ntime.h"
+#include "utils.h"
+
+#define N 200
+#define LOOP_NUM 20000000
+
+int thread_timings[N];
+
+pthread_barrier_t barrier;
+
+void loopFunc() {
+        int x = 0;
+        int i;
+        for (i = 0; i < LOOP_NUM; i++) {
+                x++;
+        }
+        return;
+}
+
+void* threadLoopFunc(void* args) {
+        pthread_barrier_wait(&barrier);
+        uint64_t st = get_time_in_nsecs();
+        loopFunc();
+        uint64_t ed = get_time_in_nsecs();
+        int el = (int) ((ed-st) / (uint64_t) 1000000);
+        *(int *)args = el;
+        return NULL;
+}
+
+int main() {
+        int j;
+        for (j = 0; j < 5; j++) loopFunc();
+        uint64_t st = get_time_in_nsecs();
+        loopFunc();
+        uint64_t ed = get_time_in_nsecs();
+        int el = (int)(ed-st) / 1000000;
+        printf("Took %d msecs with only 1 thread running\n", el);
+
+        pthread_barrier_init(&barrier, N);
+        pthread_t threads[N];
+        int i;
+        for (i = 0; i < N; i++) {
+                pthread_create(&threads[i], NULL, threadLoopFunc, &thread_timings[i]);
+        }
+        for (i = 0; i < N; i++) {
+                pthread_join(threads[i], NULL);
+        }
+        int total_msecs = 0;
+        for (i = 0; i < N; i++) {
+                total_msecs += thread_timings[i];
+        }
+        printf("Took %d msecs with %d threads", total_msecs / N, N);
+        return 0;
+}
+