PEP 418: Add bench_time.c

pep-0418/bench_time.c

@@ -0,0 +1,162 @@
+/*
+ * Benchmark program written for the PEP 418.
+ *
+ * gcc bench_time.c -O3 -lrt -o bench_time && ./bench_time
+ */
+
+#include <time.h>
+#include <stdio.h>
+#include <sys/time.h>
+
+#define NRUN 5
+#define NLOOP 1000000
+#define UNROLL(expr) \
+    expr; expr; expr; expr; expr; expr; expr; expr; expr; expr
+#define NUNROLL 10
+
+typedef struct {
+    const char *name;
+    clockid_t identifier;
+} CLOCK;
+
+CLOCK clocks[] = {
+#ifdef CLOCK_REALTIME_COARSE
+    {"CLOCK_REALTIME_COARSE", CLOCK_REALTIME_COARSE},
+#endif
+#ifdef CLOCK_MONOTONIC_COARSE
+    {"CLOCK_MONOTONIC_COARSE", CLOCK_MONOTONIC_COARSE},
+#endif
+#ifdef CLOCK_THREAD_CPUTIME_ID
+    {"CLOCK_THREAD_CPUTIME_ID", CLOCK_THREAD_CPUTIME_ID},
+#endif
+#ifdef CLOCK_PROCESS_CPUTIME_ID
+    {"CLOCK_PROCESS_CPUTIME_ID", CLOCK_PROCESS_CPUTIME_ID},
+#endif
+#ifdef CLOCK_MONOTONIC_RAW
+    {"CLOCK_MONOTONIC_RAW", CLOCK_MONOTONIC_RAW},
+#endif
+#ifdef CLOCK_VIRTUAL
+    {"CLOCK_VIRTUAL", CLOCK_VIRTUAL},
+#endif
+#ifdef CLOCK_UPTIME_FAST
+    {"CLOCK_UPTIME_FAST", CLOCK_UPTIME_FAST},
+#endif
+#ifdef CLOCK_UPTIME_PRECISE
+    {"CLOCK_UPTIME_PRECISE", CLOCK_UPTIME_PRECISE},
+#endif
+#ifdef CLOCK_UPTIME
+    {"CLOCK_UPTIME", CLOCK_UPTIME},
+#endif
+#ifdef CLOCK_MONOTONIC_FAST
+    {"CLOCK_MONOTONIC_FAST", CLOCK_MONOTONIC_FAST},
+#endif
+#ifdef CLOCK_MONOTONIC_PRECISE
+    {"CLOCK_MONOTONIC_PRECISE", CLOCK_MONOTONIC_PRECISE},
+#endif
+#ifdef CLOCK_REALTIME_FAST
+    {"CLOCK_REALTIME_FAST", CLOCK_REALTIME_FAST},
+#endif
+#ifdef CLOCK_REALTIME_PRECISE
+    {"CLOCK_REALTIME_PRECISE", CLOCK_REALTIME_PRECISE},
+#endif
+#ifdef CLOCK_SECOND
+    {"CLOCK_SECOND", CLOCK_SECOND},
+#endif
+#ifdef CLOCK_PROF
+    {"CLOCK_PROF", CLOCK_PROF},
+#endif
+    {"CLOCK_MONOTONIC", CLOCK_MONOTONIC},
+    {"CLOCK_REALTIME", CLOCK_REALTIME}
+};
+#define NCLOCKS (sizeof(clocks) / sizeof(clocks[0]))
+
+void bench_clock_gettime(clockid_t clkid)
+{
+    unsigned long loop;
+    struct timespec tmpspec;
+
+    for (loop=0; loop<NLOOP; loop++) {
+        UNROLL( (void)clock_gettime(clkid, &tmpspec) );
+    }
+}
+
+void bench_time(clockid_t clkid)
+{
+    unsigned long loop;
+    for (loop=0; loop<NLOOP; loop++) {
+        UNROLL( (void)time(NULL) );
+    }
+}
+
+void bench_usleep(clockid_t clkid)
+{
+    unsigned long loop;
+    for (loop=0; loop<NLOOP; loop++) {
+        UNROLL( (void)usleep(1000) );
+    }
+}
+
+void bench_gettimeofday(clockid_t clkid)
+{
+    unsigned long loop;
+    struct timeval tmpval;
+    for (loop=0; loop<NLOOP; loop++) {
+        UNROLL( (void)gettimeofday(&tmpval, NULL) );
+    }
+}
+
+void bench_clock(clockid_t clkid)
+{
+    unsigned long loop;
+    for (loop=0; loop<NLOOP; loop++) {
+        UNROLL( (void)clock() );
+    }
+}
+
+void benchmark(const char *name, void (*func) (clockid_t clkid), clockid_t clkid)
+{
+    unsigned int run;
+    double dt, best;
+    struct timespec before, after, tmpspec;
+    struct timeval tmpval;
+
+    best = 0;
+    for (run=0; run<NRUN; run++) {
+        clock_gettime(CLOCK_MONOTONIC, &before);
+        (*func) (clkid);
+        clock_gettime(CLOCK_MONOTONIC, &after);
+
+        dt = after.tv_sec - before.tv_sec;
+        if (after.tv_nsec >= before.tv_nsec)
+            dt += (after.tv_nsec - before.tv_nsec) * 1e-9;
+        else
+        {
+            dt -= 1.0;
+            dt += (before.tv_nsec - after.tv_nsec) * 1e-9;
+        }
+        dt *= (double)1e9 / NLOOP / NUNROLL;
+
+        if (best != 0.0) {
+            if (dt < best)
+                best = dt;
+        }
+        else
+            best = dt;
+    }
+    printf("%s: %.0f ns\n", name, best, NLOOP);
+}
+
+int main()
+{
+    clockid_t clkid;
+    int i;
+
+    for (i=0; i<NCLOCKS; i++) {
+        benchmark(clocks[i].name, bench_clock_gettime, clocks[i].identifier);
+    }
+    benchmark("clock()", bench_clock, 0);
+    benchmark("gettimeofday()", bench_gettimeofday, 0);
+    benchmark("time()", bench_time, 0);
+    return 0;
+}
+