deps/v8/test/mjsunit/math-exp-precision.js - main - githubmirror/node

deps/v8/test/mjsunit/math-exp-precision.js
64 строки3 KB
Trevor Norris
deps: update v8 to 3.17.13
20 мар 2013, 04:11
20 мар 2013, 04:1183261e7
// Copyright 2012 the V8 project authors. All rights reserved.
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
//       notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
//       copyright notice, this list of conditions and the following
//       disclaimer in the documentation and/or other materials provided
//       with the distribution.
//     * Neither the name of Google Inc. nor the names of its
//       contributors may be used to endorse or promote products derived
//       from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

// Tests that the --fast-math implementation of Math.exp() has
// reasonable precision.

function exp(x) {
  return Math.exp(x);
}

var first_call_result = exp(Math.PI);
var second_call_result = exp(Math.PI);

function assertAlmostEquals(expected, actual, x) {
  if (expected == 0 && actual == 0) return;  // OK
  if (expected == Number.POSITIVE_INFINITY &&
      actual == Number.POSITIVE_INFINITY) {
    return;  // OK
  }
  relative_diff = Math.abs(expected/actual - 1);
  assertTrue(relative_diff < 1e-12, "relative difference of " + relative_diff +
                                    " for input " + x);
}

var increment = Math.PI / 35;  // Roughly 0.1, but we want to try many
                               // different mantissae.
for (var x = -708; x < 710; x += increment) {
  var ex = exp(x);
  var reference = Math.pow(Math.E, x);
  assertAlmostEquals(reference, ex, x);
  if (ex > 0 && isFinite(ex)) {
    var back = Math.log(ex);
    assertAlmostEquals(x, back, x + " (backwards)");
  }
}

// Make sure optimizing the function does not alter the result.
var last_call_result = exp(Math.PI);
assertEquals(first_call_result, second_call_result);
assertEquals(first_call_result, last_call_result);