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sourceRevisionAtLastExport: 33f2fb0e53d135f0ee17cfccd9d993eb2a6f47de targetRevisionAtLastExport: 31340cbd9add103f586d501b0c3354b7b182abc0
79 lines
2.9 KiB
JavaScript
79 lines
2.9 KiB
JavaScript
// Copyright 2014 the V8 project authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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// Flags: --no-fast-math
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assertTrue(isNaN(Math.expm1(NaN)));
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assertTrue(isNaN(Math.expm1(function() {})));
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assertTrue(isNaN(Math.expm1({ toString: function() { return NaN; } })));
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assertTrue(isNaN(Math.expm1({ valueOf: function() { return "abc"; } })));
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assertEquals(Infinity, 1/Math.expm1(0));
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assertEquals(-Infinity, 1/Math.expm1(-0));
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assertEquals(Infinity, Math.expm1(Infinity));
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assertEquals(-1, Math.expm1(-Infinity));
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// Sanity check:
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// Math.expm1(x) stays reasonably close to Math.exp(x) - 1 for large values.
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for (var x = 1; x < 700; x += 0.25) {
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var expected = Math.exp(x) - 1;
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assertEqualsDelta(expected, Math.expm1(x), expected * 1E-15);
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expected = Math.exp(-x) - 1;
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assertEqualsDelta(expected, Math.expm1(-x), -expected * 1E-15);
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}
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// Approximation for values close to 0:
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// Use six terms of Taylor expansion at 0 for exp(x) as test expectation:
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// exp(x) - 1 == exp(0) + exp(0) * x + x * x / 2 + ... - 1
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// == x + x * x / 2 + x * x * x / 6 + ...
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function expm1(x) {
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return x * (1 + x * (1/2 + x * (
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1/6 + x * (1/24 + x * (
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1/120 + x * (1/720 + x * (
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1/5040 + x * (1/40320 + x*(
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1/362880 + x * (1/3628800))))))))));
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}
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// Sanity check:
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// Math.expm1(x) stays reasonabliy close to the Taylor series for small values.
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for (var x = 1E-1; x > 1E-300; x *= 0.8) {
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var expected = expm1(x);
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assertEqualsDelta(expected, Math.expm1(x), expected * 1E-15);
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}
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// Tests related to the fdlibm implementation.
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// Test overflow.
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assertEquals(Infinity, Math.expm1(709.8));
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// Test largest double value.
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assertEquals(Infinity, Math.exp(1.7976931348623157e308));
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// Cover various code paths.
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assertEquals(-1, Math.expm1(-56 * Math.LN2));
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assertEquals(-1, Math.expm1(-50));
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// Test most negative double value.
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assertEquals(-1, Math.expm1(-1.7976931348623157e308));
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// Test argument reduction.
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// Cases for 0.5*log(2) < |x| < 1.5*log(2).
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assertEquals(Math.E - 1, Math.expm1(1));
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assertEquals(1/Math.E - 1, Math.expm1(-1));
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// Cases for 1.5*log(2) < |x|.
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assertEquals(6.38905609893065, Math.expm1(2));
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assertEquals(-0.8646647167633873, Math.expm1(-2));
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// Cases where Math.expm1(x) = x.
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assertEquals(0, Math.expm1(0));
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assertEquals(Math.pow(2,-55), Math.expm1(Math.pow(2,-55)));
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// Tests for the case where argument reduction has x in the primary range.
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// Test branch for k = 0.
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assertEquals(0.18920711500272105, Math.expm1(0.25 * Math.LN2));
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// Test branch for k = -1.
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assertEquals(-0.5, Math.expm1(-Math.LN2));
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// Test branch for k = 1.
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assertEquals(1, Math.expm1(Math.LN2));
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// Test branch for k <= -2 || k > 56. k = -3.
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assertEquals(1.4411518807585582e17, Math.expm1(57 * Math.LN2));
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// Test last branch for k < 20, k = 19.
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assertEquals(524286.99999999994, Math.expm1(19 * Math.LN2));
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// Test the else branch, k = 20.
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assertEquals(1048575, Math.expm1(20 * Math.LN2));
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