8302028: Port fdlibm atan2 to Java

Reviewed-by: bpb
This commit is contained in:
Joe Darcy 2023-02-22 22:49:59 +00:00
parent 07e976ac26
commit fcaf871408
6 changed files with 615 additions and 28 deletions

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@ -394,6 +394,116 @@ class FdLibm {
}
}
/**
* Returns the angle theta from the conversion of rectangular
* coordinates (x, y) to polar coordinates (r, theta).
*
* Method :
* 1. Reduce y to positive by atan2(y,x)=-atan2(-y,x).
* 2. Reduce x to positive by (if x and y are unexceptional):
* ARG (x+iy) = arctan(y/x) ... if x > 0,
* ARG (x+iy) = pi - arctan[y/(-x)] ... if x < 0,
*
* Special cases:
*
* ATAN2((anything), NaN ) is NaN;
* ATAN2(NAN , (anything) ) is NaN;
* ATAN2(+-0, +(anything but NaN)) is +-0 ;
* ATAN2(+-0, -(anything but NaN)) is +-pi ;
* ATAN2(+-(anything but 0 and NaN), 0) is +-pi/2;
* ATAN2(+-(anything but INF and NaN), +INF) is +-0 ;
* ATAN2(+-(anything but INF and NaN), -INF) is +-pi;
* ATAN2(+-INF,+INF ) is +-pi/4 ;
* ATAN2(+-INF,-INF ) is +-3pi/4;
* ATAN2(+-INF, (anything but,0,NaN, and INF)) is +-pi/2;
*
* Constants:
* The hexadecimal values are the intended ones for the following
* constants. The decimal values may be used, provided that the
* compiler will convert from decimal to binary accurately enough
* to produce the hexadecimal values shown.
*/
static class Atan2 {
private Atan2() {throw new UnsupportedOperationException();}
private static final double
tiny = 1.0e-300,
pi_o_4 = 0x1.921fb54442d18p-1, // 7.8539816339744827900E-01
pi_o_2 = 0x1.921fb54442d18p0, // 1.5707963267948965580E+00
pi_lo = 0x1.1a62633145c07p-53; // 1.2246467991473531772E-16
static double compute(double y, double x) {
double z;
int k, m, hx, hy, ix, iy;
/*unsigned*/ int lx, ly;
hx = __HI(x);
ix = hx & 0x7fff_ffff;
lx = __LO(x);
hy = __HI(y);
iy = hy&0x7fff_ffff;
ly = __LO(y);
if (Double.isNaN(x) || Double.isNaN(y))
return x + y;
if (((hx - 0x3ff0_0000) | lx) == 0) // x = 1.0
return StrictMath.atan(y);
m = ((hy >> 31) & 1)|((hx >> 30) & 2); // 2*sign(x) + sign(y)
// when y = 0
if ((iy | ly) == 0) {
switch(m) {
case 0:
case 1: return y; // atan(+/-0, +anything) = +/-0
case 2: return Math.PI + tiny; // atan(+0, -anything) = pi
case 3: return -Math.PI - tiny; // atan(-0, -anything) = -pi
}
}
// when x = 0
if ((ix | lx) == 0) {
return (hy < 0)? -pi_o_2 - tiny : pi_o_2 + tiny;
}
// when x is INF
if (ix == 0x7ff0_0000) {
if (iy == 0x7ff0_0000) {
switch(m) {
case 0: return pi_o_4 + tiny; // atan(+INF, +INF)
case 1: return -pi_o_4 - tiny; // atan(-INF, +INF)
case 2: return 3.0*pi_o_4 + tiny; // atan(+INF, -INF)
case 3: return -3.0*pi_o_4 - tiny; // atan(-INF, -INF)
}
} else {
switch(m) {
case 0: return 0.0; // atan(+..., +INF)
case 1: return -0.0; // atan(-..., +INF)
case 2: return Math.PI + tiny; // atan(+..., -INF)
case 3: return -Math.PI - tiny; // atan(-..., -INF)
}
}
}
// when y is INF
if (iy == 0x7ff0_0000) {
return (hy < 0)? -pi_o_2 - tiny : pi_o_2 + tiny;
}
// compute y/x
k = (iy - ix) >> 20;
if (k > 60) { // |y/x| > 2**60
z = pi_o_2+0.5*pi_lo;
} else if (hx < 0 && k < -60) { // |y|/x < -2**60
z = 0.0;
} else { // safe to do y/x
z = StrictMath.atan(Math.abs(y/x));
}
switch (m) {
case 0: return z; // atan(+, +)
case 1: return -z; // atan(-, +)
case 2: return Math.PI - (z - pi_lo); // atan(+, -)
default: return (z - pi_lo) - Math.PI; // atan(-, -), case 3
}
}
}
/**
* cbrt(x)
* Return cube root of x

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@ -547,7 +547,9 @@ public final class StrictMath {
* in polar coordinates that corresponds to the point
* (<i>x</i>,&nbsp;<i>y</i>) in Cartesian coordinates.
*/
public static native double atan2(double y, double x);
public static double atan2(double y, double x) {
return FdLibm.Atan2.compute(y, x);
}
/**
* Returns the value of the first argument raised to the power of the

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@ -1,5 +1,5 @@
/*
* Copyright (c) 2004, 2022, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2004, 2023, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
@ -23,36 +23,14 @@
/*
* @test
* @bug 4984407
* @bug 4984407 8302028
* @summary Tests for {Math, StrictMath}.atan2
*/
public class Atan2Tests {
private Atan2Tests(){}
static int testAtan2Case(double input1, double input2, double expected) {
int failures = 0;
failures += Tests.test("StrictMath.atan2", input1, input2, StrictMath::atan2, expected);
failures += Tests.test("Math.atan2", input1, input2, Math::atan2, expected);
return failures;
}
static int testAtan2() {
int failures = 0;
double [][] testCases = {
{-3.0, Double.POSITIVE_INFINITY, -0.0},
};
for (double[] testCase : testCases) {
failures+=testAtan2Case(testCase[0], testCase[1], testCase[2]);
}
return failures;
}
public static void main(String... argv) {
public static void main(String... args) {
int failures = 0;
failures += testAtan2();
@ -63,4 +41,202 @@ public class Atan2Tests {
throw new RuntimeException();
}
}
/**
* Special cases from the spec interspersed with test cases.
*/
private static int testAtan2() {
int failures = 0;
double NaNd = Double.NaN;
double MIN_VALUE = Double.MIN_VALUE;
double MIN_NORM = Double.MIN_NORMAL;
double MAX_VALUE = Double.MAX_VALUE;
double InfinityD = Double.POSITIVE_INFINITY;
double PI = Math.PI;
/*
* If either argument is NaN, then the result is NaN.
*/
for(double nan : Tests.NaNs) {
failures += testAtan2Case(nan, 0.0, NaNd);
failures += testAtan2Case(0.0, nan, NaNd);
}
double [][] testCases = {
/*
* If the first argument is positive zero and the second
* argument is positive, or the first argument is positive
* and finite and the second argument is positive
* infinity, then the result is positive zero.
*/
{+0.0, MIN_VALUE, +0.0},
{+0.0, MIN_NORM, +0.0},
{+0.0, 1.0, +0.0},
{+0.0, MAX_VALUE, +0.0},
{+0.0, InfinityD, +0.0},
{MIN_VALUE, InfinityD, +0.0},
{MIN_NORM, InfinityD, +0.0},
{1.0, InfinityD, +0.0},
{MAX_VALUE, InfinityD, +0.0},
{MIN_VALUE, InfinityD, +0.0},
/*
* If the first argument is negative zero and the second
* argument is positive, or the first argument is negative
* and finite and the second argument is positive
* infinity, then the result is negative zero.
*/
{-0.0, MIN_VALUE, -0.0},
{-0.0, MIN_NORM, -0.0},
{-0.0, 1.0, -0.0},
{-0.0, MAX_VALUE, -0.0},
{-0.0, InfinityD, -0.0},
{-MIN_VALUE, InfinityD, -0.0},
{-MIN_NORM, InfinityD, -0.0},
{-1.0, InfinityD, -0.0},
{-MAX_VALUE, InfinityD, -0.0},
/*
* If the first argument is positive zero and the second
* argument is negative, or the first argument is positive
* and finite and the second argument is negative
* infinity, then the result is the double value closest
* to pi.
*/
{+0.0, -MIN_VALUE, PI},
{+0.0, -MIN_NORM, PI},
{+0.0, -1.0, PI},
{+0.0, -MAX_VALUE, PI},
{+0.0, -InfinityD, PI},
{MIN_VALUE, -InfinityD, PI},
{MIN_NORM, -InfinityD, PI},
{1.0, -InfinityD, PI},
{MAX_VALUE, -InfinityD, PI},
/*
* If the first argument is negative zero and the second
* argument is negative, or the first argument is negative
* and finite and the second argument is negative
* infinity, then the result is the double value closest
* to -pi.
*/
{-0.0, -MIN_VALUE, -PI},
{-0.0, -MIN_NORM, -PI},
{-0.0, -1.0, -PI},
{-0.0, -MAX_VALUE, -PI},
{-0.0, -InfinityD, -PI},
{-MIN_VALUE, -InfinityD, -PI},
{-MIN_NORM, -InfinityD, -PI},
{-1.0, -InfinityD, -PI},
{-MAX_VALUE, -InfinityD, -PI},
/*
* If the first argument is positive and the second
* argument is positive zero or negative zero, or the
* first argument is positive infinity and the second
* argument is finite, then the result is the double value
* closest to pi/2.
*/
{MIN_VALUE, +0.0, PI/2.0},
{MIN_NORM, +0.0, PI/2.0},
{1.0, +0.0, PI/2.0},
{MAX_VALUE, +0.0, PI/2.0},
{MIN_VALUE, -0.0, PI/2.0},
{MIN_VALUE, -0.0, PI/2.0},
{MIN_NORM, -0.0, PI/2.0},
{1.0, -0.0, PI/2.0},
{MAX_VALUE, -0.0, PI/2.0},
{InfinityD, -MIN_VALUE, PI/2.0},
{InfinityD, -MIN_NORM, PI/2.0},
{InfinityD, -1.0, PI/2.0},
{InfinityD, -MAX_VALUE, PI/2.0},
{InfinityD, MIN_VALUE, PI/2.0},
{InfinityD, MIN_NORM, PI/2.0},
{InfinityD, 1.0, PI/2.0},
{InfinityD, MAX_VALUE, PI/2.0},
/*
* If the first argument is negative and the second argument is
* positive zero or negative zero, or the first argument is
* negative infinity and the second argument is finite, then the
* result is the double value closest to -pi/2.
*/
{-MIN_VALUE, +0.0, -PI/2.0},
{-MIN_NORM, +0.0, -PI/2.0},
{-1.0, +0.0, -PI/2.0},
{-MAX_VALUE, +0.0, -PI/2.0},
{-MIN_VALUE, -0.0, -PI/2.0},
{-MIN_VALUE, -0.0, -PI/2.0},
{-MIN_NORM, -0.0, -PI/2.0},
{-1.0, -0.0, -PI/2.0},
{-MAX_VALUE, -0.0, -PI/2.0},
{-InfinityD, -MIN_VALUE, -PI/2.0},
{-InfinityD, -MIN_NORM, -PI/2.0},
{-InfinityD, -1.0, -PI/2.0},
{-InfinityD, -MAX_VALUE, -PI/2.0},
{-InfinityD, MIN_VALUE, -PI/2.0},
{-InfinityD, MIN_NORM, -PI/2.0},
{-InfinityD, 1.0, -PI/2.0},
{-InfinityD, MAX_VALUE, -PI/2.0},
/*
* If both arguments are positive infinity, then the result is the
* double value closest to pi/4.
*/
{InfinityD, InfinityD, PI/4.0},
/*
* If the first argument is positive infinity and the
* second argument is negative infinity, then the result
* is the double value closest to 3*pi/4.
*/
// Note: in terms of computation, the result of the double
// expression
// 3*PI/4.0
// is the same as a high-precision decimal value of pi
// scaled accordingly and rounded to double:
// BigDecimal bdPi = new BigDecimal("3.14159265358979323846264338327950288419716939937510");
// bdPi.multiply(BigDecimal.valueOf(3)).divide(BigDecimal.valueOf(4)).doubleValue();
{InfinityD, -InfinityD, 3*PI/4.0},
/*
* If the first argument is negative infinity and the second
* argument is positive infinity, then the result is the double
* value closest to -pi/4.
*/
{-InfinityD, InfinityD, -PI/4.0},
/*
* If both arguments are negative infinity, then the result is the
* double value closest to -3*pi/4.
*/
{-InfinityD, -InfinityD, -3*PI/4.0},
{-3.0, InfinityD, -0.0},
};
for (double[] testCase : testCases) {
failures += testAtan2Case(testCase[0], testCase[1], testCase[2]);
}
return failures;
}
private static int testAtan2Case(double input1, double input2, double expected) {
int failures = 0;
failures += Tests.test("StrictMath.atan2", input1, input2, StrictMath::atan2, expected);
failures += Tests.test("Math.atan2", input1, input2, Math::atan2, expected);
return failures;
}
}

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@ -0,0 +1,191 @@
/*
* Copyright (c) 2003, 2023, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
/*
* @test
* @bug 4851638
* @key randomness
* @summary Tests for StrictMath.atan2
* @library /test/lib
* @build jdk.test.lib.RandomFactory
* @build Tests
* @build FdlibmTranslit
* @build Atan2Tests
* @run main Atan2Tests
*/
import jdk.test.lib.RandomFactory;
/**
* The tests in ../Math/Atan2Tests.java test properties that should
* hold for any atan2 implementation, including the FDLIBM-based one
* required for StrictMath.atan2. Therefore, the test cases in
* ../Math/Atan2Tests.java are run against both the Math and
* StrictMath versions of atan2. The role of this test is to verify
* that the FDLIBM atan2 algorithm is being used by running golden
* file tests on values that may vary from one conforming atan2
* implementation to another.
*/
public class Atan2Tests {
private Atan2Tests(){}
public static void main(String... args) {
int failures = 0;
failures += testAgainstTranslit();
if (failures > 0) {
System.err.println("Testing atan2 incurred "
+ failures + " failures.");
throw new RuntimeException();
}
}
// Initialize shared random number generator
private static java.util.Random random = RandomFactory.getRandom();
/**
* Test StrictMath.atan2 against transliteration port of atan2.
*/
private static int testAgainstTranslit() {
int failures = 0;
double MIN_VALUE = Double.MIN_VALUE;
double MIN_NORM = Double.MIN_NORMAL;
double MAX_VALUE = Double.MAX_VALUE;
double InfinityD = Double.POSITIVE_INFINITY;
double PI = Math.PI;
// The exact special cases for infinity, NaN, zero,
// etc. inputs are checked in the Math tests.
// Test exotic NaN bit patterns
double[][] exoticNaNs = {
{Double.longBitsToDouble(0x7FF0_0000_0000_0001L), 0.0},
{0.0, Double.longBitsToDouble(0x7FF0_0000_0000_0001L)},
{Double.longBitsToDouble(0xFFF_00000_0000_0001L), 0.0},
{0.0, Double.longBitsToDouble(0xFFF0_0000_0000_0001L)},
{Double.longBitsToDouble(0x7FF_00000_7FFF_FFFFL), 0.0},
{0.0, Double.longBitsToDouble(0x7FF0_7FFF_0000_FFFFL)},
{Double.longBitsToDouble(0xFFF_00000_7FFF_FFFFL), 0.0},
{0.0, Double.longBitsToDouble(0xFFF0_7FFF_0000_FFFFL)},
};
for (double[] exoticNaN: exoticNaNs) {
failures += testAtan2Case(exoticNaN[0], exoticNaN[1],
FdlibmTranslit.atan2(exoticNaN[0], exoticNaN[1]));
}
// Probe near decision points in the FDLIBM algorithm.
double[][] decisionPoints = {
// If x == 1, return atan(y)
{0.5, Math.nextDown(1.0)},
{0.5, 1.0},
{0.5, Math.nextUp(1.0)},
{ MIN_VALUE, MIN_VALUE},
{ MIN_VALUE, -MIN_VALUE},
{-MIN_VALUE, MIN_VALUE},
{-MIN_VALUE, -MIN_VALUE},
{ MAX_VALUE, MAX_VALUE},
{ MAX_VALUE, -MAX_VALUE},
{-MAX_VALUE, MAX_VALUE},
{-MAX_VALUE, -MAX_VALUE},
{ MIN_VALUE, MAX_VALUE},
{ MAX_VALUE, MIN_VALUE},
{-MIN_VALUE, MAX_VALUE},
{-MAX_VALUE, MIN_VALUE},
{MIN_VALUE, -MAX_VALUE},
{MAX_VALUE, -MIN_VALUE},
{-MIN_VALUE, -MAX_VALUE},
{-MAX_VALUE, -MIN_VALUE},
};
for (double[] decisionPoint: decisionPoints) {
failures += testAtan2Case(decisionPoint[0], decisionPoint[1],
FdlibmTranslit.atan2(decisionPoint[0], decisionPoint[1]));
}
// atan2 looks at the ratio y/x and executes different code
// paths accordingly: tests for 2^60 and 2^-60.
double y = 1.0;
double x = 0x1.0p60;
double increment_x = Math.ulp(x);
double increment_y = Math.ulp(y);
y = y - 128*increment_y;
x = x - 128*increment_x;
for (int i = 0; i < 256; i++, x += increment_x) {
for (int j = 0; j < 256; j++, y += increment_y) {
failures += testAtan2Case( y, x, FdlibmTranslit.atan2( y, x));
failures += testAtan2Case(-y, x, FdlibmTranslit.atan2(-y, x));
failures += testAtan2Case( y, -x, FdlibmTranslit.atan2( y, -x));
failures += testAtan2Case(-y, -x, FdlibmTranslit.atan2(-y, -x));
failures += testAtan2Case( 2.0*y, 2.0*x, FdlibmTranslit.atan2( 2.0*y, 2.0*x));
failures += testAtan2Case(-2.0*y, 2.0*x, FdlibmTranslit.atan2(-2.0*y, 2.0*x));
failures += testAtan2Case( 2.0*y, -2.0*x, FdlibmTranslit.atan2( 2.0*y, -2.0*x));
failures += testAtan2Case(-2.0*y, -2.0*x, FdlibmTranslit.atan2(-2.0*y, -2.0*x));
failures += testAtan2Case( 0.5*y, 0.5*x, FdlibmTranslit.atan2( 0.5*y, 0.5*x));
failures += testAtan2Case(-0.5*y, 0.5*x, FdlibmTranslit.atan2(-0.5*y, 0.5*x));
failures += testAtan2Case( 0.5*y, -0.5*x, FdlibmTranslit.atan2( 0.5*y, -0.5*x));
failures += testAtan2Case(-0.5*y, -0.5*x, FdlibmTranslit.atan2(-0.5*y, -0.5*x));
// Switch argument position
failures += testAtan2Case( x, y, FdlibmTranslit.atan2( x, y));
failures += testAtan2Case(-x, y, FdlibmTranslit.atan2(-x, y));
failures += testAtan2Case( x, -y, FdlibmTranslit.atan2( x, -y));
failures += testAtan2Case(-x, -y, FdlibmTranslit.atan2(-x, -y));
failures += testAtan2Case( 0.5*x, 0.5*y, FdlibmTranslit.atan2( 0.5*x, 0.5*y));
failures += testAtan2Case(-0.5*x, 0.5*y, FdlibmTranslit.atan2(-0.5*x, 0.5*y));
failures += testAtan2Case( 0.5*x, -0.5*y, FdlibmTranslit.atan2( 0.5*x, -0.5*y));
failures += testAtan2Case(-0.5*x, -0.5*y, FdlibmTranslit.atan2(-0.5*x, -0.5*y));
}
}
// Check random values
for (int k = 0; k < 200; k++ ) {
y = random.nextDouble();
x = random.nextDouble();
failures += testAtan2Case(y, x, FdlibmTranslit.atan2(y, x));
}
return failures;
}
private static int testAtan2Case(double input1, double input2, double expected) {
int failures = 0;
failures += Tests.test("StrictMath.atan2(double)", input1, input2,
StrictMath::atan2, expected);
return failures;
}
}

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@ -23,7 +23,7 @@
/*
* @test
* @bug 8301833 8302026 8301444
* @bug 8301833 8302026 8301444 8302028
* @build Tests
* @build FdlibmTranslit
* @build ExhaustingTests
@ -130,7 +130,7 @@ public class ExhaustingTests {
// probes).
BinaryTestCase[] testCases = {
new BinaryTestCase("hypot", FdlibmTranslit::hypot, StrictMath::hypot, 20, 20),
// new BinaryTestCase("atan2", FdlibmTranslit::atan2, StrictMath::atan2, 20, 20),
new BinaryTestCase("atan2", FdlibmTranslit::atan2, StrictMath::atan2, 20, 20),
};
for (var testCase : testCases) {

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@ -82,6 +82,10 @@ public class FdlibmTranslit {
return Atan.compute(x);
}
public static double atan2(double y, double x) {
return Atan2.compute(y, x);
}
public static double hypot(double x, double y) {
return Hypot.compute(x, y);
}
@ -396,6 +400,110 @@ public class FdlibmTranslit {
}
}
/**
* Returns the angle theta from the conversion of rectangular
* coordinates (x, y) to polar coordinates (r, theta).
*
* Method :
* 1. Reduce y to positive by atan2(y,x)=-atan2(-y,x).
* 2. Reduce x to positive by (if x and y are unexceptional):
* ARG (x+iy) = arctan(y/x) ... if x > 0,
* ARG (x+iy) = pi - arctan[y/(-x)] ... if x < 0,
*
* Special cases:
*
* ATAN2((anything), NaN ) is NaN;
* ATAN2(NAN , (anything) ) is NaN;
* ATAN2(+-0, +(anything but NaN)) is +-0 ;
* ATAN2(+-0, -(anything but NaN)) is +-pi ;
* ATAN2(+-(anything but 0 and NaN), 0) is +-pi/2;
* ATAN2(+-(anything but INF and NaN), +INF) is +-0 ;
* ATAN2(+-(anything but INF and NaN), -INF) is +-pi;
* ATAN2(+-INF,+INF ) is +-pi/4 ;
* ATAN2(+-INF,-INF ) is +-3pi/4;
* ATAN2(+-INF, (anything but,0,NaN, and INF)) is +-pi/2;
*
* Constants:
* The hexadecimal values are the intended ones for the following
* constants. The decimal values may be used, provided that the
* compiler will convert from decimal to binary accurately enough
* to produce the hexadecimal values shown.
*/
static class Atan2 {
private static final double
tiny = 1.0e-300,
zero = 0.0,
pi_o_4 = 7.8539816339744827900E-01, /* 0x3FE921FB, 0x54442D18 */
pi_o_2 = 1.5707963267948965580E+00, /* 0x3FF921FB, 0x54442D18 */
pi = 3.1415926535897931160E+00, /* 0x400921FB, 0x54442D18 */
pi_lo = 1.2246467991473531772E-16; /* 0x3CA1A626, 0x33145C07 */
static double compute(double y, double x) {
double z;
int k,m,hx,hy,ix,iy;
/*unsigned*/ int lx,ly;
hx = __HI(x); ix = hx&0x7fffffff;
lx = __LO(x);
hy = __HI(y); iy = hy&0x7fffffff;
ly = __LO(y);
if(((ix|((lx|-lx)>>>31))>0x7ff00000)|| // Note unsigned shifts
((iy|((ly|-ly)>>>31))>0x7ff00000)) /* x or y is NaN */
return x+y;
if(((hx-0x3ff00000)|lx)==0) return atan(y); /* x=1.0 */
m = ((hy>>31)&1)|((hx>>30)&2); /* 2*sign(x)+sign(y) */
/* when y = 0 */
if((iy|ly)==0) {
switch(m) {
case 0:
case 1: return y; /* atan(+-0,+anything)=+-0 */
case 2: return pi+tiny;/* atan(+0,-anything) = pi */
case 3: return -pi-tiny;/* atan(-0,-anything) =-pi */
}
}
/* when x = 0 */
if((ix|lx)==0) return (hy<0)? -pi_o_2-tiny: pi_o_2+tiny;
/* when x is INF */
if(ix==0x7ff00000) {
if(iy==0x7ff00000) {
switch(m) {
case 0: return pi_o_4+tiny;/* atan(+INF,+INF) */
case 1: return -pi_o_4-tiny;/* atan(-INF,+INF) */
case 2: return 3.0*pi_o_4+tiny;/*atan(+INF,-INF)*/
case 3: return -3.0*pi_o_4-tiny;/*atan(-INF,-INF)*/
}
} else {
switch(m) {
case 0: return zero ; /* atan(+...,+INF) */
case 1: return -1.0*zero ; /* atan(-...,+INF) */
case 2: return pi+tiny ; /* atan(+...,-INF) */
case 3: return -pi-tiny ; /* atan(-...,-INF) */
}
}
}
/* when y is INF */
if(iy==0x7ff00000) return (hy<0)? -pi_o_2-tiny: pi_o_2+tiny;
/* compute y/x */
k = (iy-ix)>>20;
if(k > 60) z=pi_o_2+0.5*pi_lo; /* |y/x| > 2**60 */
else if(hx<0&&k<-60) z=0.0; /* |y|/x < -2**60 */
else z=atan(Math.abs(y/x)); /* safe to do y/x */
switch (m) {
case 0: return z ; /* atan(+,+) */
case 1:
// original:__HI(z) ^= 0x80000000;
z = __HI(z, __HI(z) ^ 0x80000000);
return z ; /* atan(-,+) */
case 2: return pi-(z-pi_lo);/* atan(+,-) */
default: /* case 3 */
return (z-pi_lo)-pi;/* atan(-,-) */
}
}
}
/**
* cbrt(x)
* Return cube root of x