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// Copyright 2013 The Emscripten Authors. All rights reserved.
// Emscripten is available under two separate licenses, the MIT license and the
// University of Illinois/NCSA Open Source License. Both these licenses can be
// found in the LICENSE file.
#include <assert.h>
#include <stdio.h>
#include "emscripten.h"
const double good_enough = 5.0; // good as we can do, given spectre...
int main() {
// This code tests three things:
// a) Calling emscripten_get_now(), time actually proceeds.
// b) Values returned by emscripten_get_now() are strictly nondecreasing.
// c) emscripten_get_now() is able to return sub-millisecond precision timer values.
double smallest_delta = 1000.f;
double start = emscripten_get_now();
while (1) { // Have several attempts to find a good small delta, i.e. give time to JS engine to warm up the code and so on.
double t = emscripten_get_now();
if (t - start >= 5000) {
printf("We waited long enough, %f ms\n", t - start);
break;
}
double t2 = t;
while (t2 == t) {
t2 = emscripten_get_now();
}
double delta = t2 - t;
if (delta < 0.) { // Timer must be monotonous.
printf("Timer is not monotonous!\n");
return 1;
}
if (delta < smallest_delta) {
smallest_delta = delta;
if (delta <= good_enough) {
break;
}
}
}
if (smallest_delta <= 0.) {
printf("Smallest delta is invalid %f\n", smallest_delta);
return 1;
}
printf("Timer resolution (smallest delta): %.20f msecs\n", smallest_delta);
if (smallest_delta <= good_enough) {
printf("Timer resolution is good (or as good as spectre allows...).\n");
return 0;
}
printf("Error: Bad timer precision, too large\n");
assert(false);
return 1;
}
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