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27
28// Tests that the --fast-math implementation of Math.exp() has
29// reasonable precision.
30
31function exp(x) {
32  return Math.exp(x);
33}
34
35var first_call_result = exp(Math.PI);
36var second_call_result = exp(Math.PI);
37
38function assertAlmostEquals(expected, actual, x) {
39  if (expected == 0 && actual == 0) return;  // OK
40  if (expected == Number.POSITIVE_INFINITY &&
41      actual == Number.POSITIVE_INFINITY) {
42    return;  // OK
43  }
44  relative_diff = Math.abs(expected/actual - 1);
45  assertTrue(relative_diff < 1e-12, "relative difference of " + relative_diff +
46                                    " for input " + x);
47}
48
49var increment = Math.PI / 35;  // Roughly 0.1, but we want to try many
50                               // different mantissae.
51for (var x = -708; x < 710; x += increment) {
52  var ex = exp(x);
53  var reference = Math.pow(Math.E, x);
54  assertAlmostEquals(reference, ex, x);
55  if (ex > 0 && isFinite(ex)) {
56    var back = Math.log(ex);
57    assertAlmostEquals(x, back, x + " (backwards)");
58  }
59}
60
61// Make sure optimizing the function does not alter the result.
62var last_call_result = exp(Math.PI);
63assertEquals(first_call_result, second_call_result);
64assertEquals(first_call_result, last_call_result);
65