Initial Jack import.

Change-Id: I953cf0a520195a7187d791b2885848ad0d5a9b43

1 files changed, 379 insertions, 0 deletions

diff --git a/guava/src/com/google/common/math/DoubleMath.java b/guava/src/com/google/common/math/DoubleMath.java
new file mode 100644
index 0000000..95e8fb4
--- /dev/null
+++ b/guava/src/com/google/common/math/DoubleMath.java
@@ -0,0 +1,379 @@
+/*
+ * Copyright (C) 2011 The Guava Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.common.math;
+
+import static com.google.common.base.Preconditions.checkArgument;
+import static com.google.common.math.DoubleUtils.IMPLICIT_BIT;
+import static com.google.common.math.DoubleUtils.SIGNIFICAND_BITS;
+import static com.google.common.math.DoubleUtils.getSignificand;
+import static com.google.common.math.DoubleUtils.isFinite;
+import static com.google.common.math.DoubleUtils.isNormal;
+import static com.google.common.math.DoubleUtils.scaleNormalize;
+import static com.google.common.math.MathPreconditions.checkInRange;
+import static com.google.common.math.MathPreconditions.checkNonNegative;
+import static com.google.common.math.MathPreconditions.checkRoundingUnnecessary;
+import static java.lang.Math.abs;
+import static java.lang.Math.copySign;
+import static java.lang.Math.getExponent;
+import static java.lang.Math.log;
+import static java.lang.Math.rint;
+
+import com.google.common.annotations.Beta;
+import com.google.common.annotations.VisibleForTesting;
+import com.google.common.primitives.Booleans;
+
+import java.math.BigInteger;
+import java.math.RoundingMode;
+
+/**
+ * A class for arithmetic on doubles that is not covered by {@link java.lang.Math}.
+ *
+ * @author Louis Wasserman
+ * @since 11.0
+ */
+@Beta
+public final class DoubleMath {
+  /*
+   * This method returns a value y such that rounding y DOWN (towards zero) gives the same result
+   * as rounding x according to the specified mode.
+   */
+  static double roundIntermediate(double x, RoundingMode mode) {
+    if (!isFinite(x)) {
+      throw new ArithmeticException("input is infinite or NaN");
+    }
+    switch (mode) {
+      case UNNECESSARY:
+        checkRoundingUnnecessary(isMathematicalInteger(x));
+        return x;
+
+      case FLOOR:
+        if (x >= 0.0 || isMathematicalInteger(x)) {
+          return x;
+        } else {
+          return x - 1.0;
+        }
+
+      case CEILING:
+        if (x <= 0.0 || isMathematicalInteger(x)) {
+          return x;
+        } else {
+          return x + 1.0;
+        }
+
+      case DOWN:
+        return x;
+
+      case UP:
+        if (isMathematicalInteger(x)) {
+          return x;
+        } else {
+          return x + Math.copySign(1.0, x);
+        }
+
+      case HALF_EVEN:
+        return rint(x);
+
+      case HALF_UP: {
+        double z = rint(x);
+        if (abs(x - z) == 0.5) {
+          return x + copySign(0.5, x);
+        } else {
+          return z;
+        }
+      }
+
+      case HALF_DOWN: {
+        double z = rint(x);
+        if (abs(x - z) == 0.5) {
+          return x;
+        } else {
+          return z;
+        }
+      }
+
+      default:
+        throw new AssertionError();
+    }
+  }
+
+  /**
+   * Returns the {@code int} value that is equal to {@code x} rounded with the specified rounding
+   * mode, if possible.
+   *
+   * @throws ArithmeticException if
+   *         <ul>
+   *         <li>{@code x} is infinite or NaN
+   *         <li>{@code x}, after being rounded to a mathematical integer using the specified
+   *         rounding mode, is either less than {@code Integer.MIN_VALUE} or greater than {@code
+   *         Integer.MAX_VALUE}
+   *         <li>{@code x} is not a mathematical integer and {@code mode} is
+   *         {@link RoundingMode#UNNECESSARY}
+   *         </ul>
+   */
+  public static int roundToInt(double x, RoundingMode mode) {
+    double z = roundIntermediate(x, mode);
+    checkInRange(z > MIN_INT_AS_DOUBLE - 1.0 & z < MAX_INT_AS_DOUBLE + 1.0);
+    return (int) z;
+  }
+
+  private static final double MIN_INT_AS_DOUBLE = -0x1p31;
+  private static final double MAX_INT_AS_DOUBLE = 0x1p31 - 1.0;
+
+  /**
+   * Returns the {@code long} value that is equal to {@code x} rounded with the specified rounding
+   * mode, if possible.
+   *
+   * @throws ArithmeticException if
+   *         <ul>
+   *         <li>{@code x} is infinite or NaN
+   *         <li>{@code x}, after being rounded to a mathematical integer using the specified
+   *         rounding mode, is either less than {@code Long.MIN_VALUE} or greater than {@code
+   *         Long.MAX_VALUE}
+   *         <li>{@code x} is not a mathematical integer and {@code mode} is
+   *         {@link RoundingMode#UNNECESSARY}
+   *         </ul>
+   */
+  public static long roundToLong(double x, RoundingMode mode) {
+    double z = roundIntermediate(x, mode);
+    checkInRange(MIN_LONG_AS_DOUBLE - z < 1.0 & z < MAX_LONG_AS_DOUBLE_PLUS_ONE);
+    return (long) z;
+  }
+
+  private static final double MIN_LONG_AS_DOUBLE = -0x1p63;
+  /*
+   * We cannot store Long.MAX_VALUE as a double without losing precision.  Instead, we store
+   * Long.MAX_VALUE + 1 == -Long.MIN_VALUE, and then offset all comparisons by 1.
+   */
+  private static final double MAX_LONG_AS_DOUBLE_PLUS_ONE = 0x1p63;
+
+  /**
+   * Returns the {@code BigInteger} value that is equal to {@code x} rounded with the specified
+   * rounding mode, if possible.
+   *
+   * @throws ArithmeticException if
+   *         <ul>
+   *         <li>{@code x} is infinite or NaN
+   *         <li>{@code x} is not a mathematical integer and {@code mode} is
+   *         {@link RoundingMode#UNNECESSARY}
+   *         </ul>
+   */
+  public static BigInteger roundToBigInteger(double x, RoundingMode mode) {
+    x = roundIntermediate(x, mode);
+    if (MIN_LONG_AS_DOUBLE - x < 1.0 & x < MAX_LONG_AS_DOUBLE_PLUS_ONE) {
+      return BigInteger.valueOf((long) x);
+    }
+    int exponent = getExponent(x);
+    long significand = getSignificand(x);
+    BigInteger result = BigInteger.valueOf(significand).shiftLeft(exponent - SIGNIFICAND_BITS);
+    return (x < 0) ? result.negate() : result;
+  }
+
+  /**
+   * Returns {@code true} if {@code x} is exactly equal to {@code 2^k} for some finite integer
+   * {@code k}.
+   */
+  public static boolean isPowerOfTwo(double x) {
+    return x > 0.0 && isFinite(x) && LongMath.isPowerOfTwo(getSignificand(x));
+  }
+
+  /**
+   * Returns the base 2 logarithm of a double value.
+   *
+   * <p>Special cases:
+   * <ul>
+   * <li>If {@code x} is NaN or less than zero, the result is NaN.
+   * <li>If {@code x} is positive infinity, the result is positive infinity.
+   * <li>If {@code x} is positive or negative zero, the result is negative infinity.
+   * </ul>
+   *
+   * <p>The computed result is within 1 ulp of the exact result.
+   *
+   * <p>If the result of this method will be immediately rounded to an {@code int},
+   * {@link #log2(double, RoundingMode)} is faster.
+   */
+  public static double log2(double x) {
+    return log(x) / LN_2; // surprisingly within 1 ulp according to tests
+  }
+
+  private static final double LN_2 = log(2);
+
+  /**
+   * Returns the base 2 logarithm of a double value, rounded with the specified rounding mode to an
+   * {@code int}.
+   *
+   * <p>Regardless of the rounding mode, this is faster than {@code (int) log2(x)}.
+   *
+   * @throws IllegalArgumentException if {@code x <= 0.0}, {@code x} is NaN, or {@code x} is
+   *         infinite
+   */
+  @SuppressWarnings("fallthrough")
+  public static int log2(double x, RoundingMode mode) {
+    checkArgument(x > 0.0 && isFinite(x), "x must be positive and finite");
+    int exponent = getExponent(x);
+    if (!isNormal(x)) {
+      return log2(x * IMPLICIT_BIT, mode) - SIGNIFICAND_BITS;
+      // Do the calculation on a normal value.
+    }
+    // x is positive, finite, and normal
+    boolean increment;
+    switch (mode) {
+      case UNNECESSARY:
+        checkRoundingUnnecessary(isPowerOfTwo(x));
+        // fall through
+      case FLOOR:
+        increment = false;
+        break;
+      case CEILING:
+        increment = !isPowerOfTwo(x);
+        break;
+      case DOWN:
+        increment = exponent < 0 & !isPowerOfTwo(x);
+        break;
+      case UP:
+        increment = exponent >= 0 & !isPowerOfTwo(x);
+        break;
+      case HALF_DOWN:
+      case HALF_EVEN:
+      case HALF_UP:
+        double xScaled = scaleNormalize(x);
+        // sqrt(2) is irrational, and the spec is relative to the "exact numerical result,"
+        // so log2(x) is never exactly exponent + 0.5.
+        increment = (xScaled * xScaled) > 2.0;
+        break;
+      default:
+        throw new AssertionError();
+    }
+    return increment ? exponent + 1 : exponent;
+  }
+
+  /**
+   * Returns {@code true} if {@code x} represents a mathematical integer.
+   *
+   * <p>This is equivalent to, but not necessarily implemented as, the expression {@code
+   * !Double.isNaN(x) && !Double.isInfinite(x) && x == Math.rint(x)}.
+   */
+  public static boolean isMathematicalInteger(double x) {
+    return isFinite(x)
+        && (x == 0.0 ||
+            SIGNIFICAND_BITS - Long.numberOfTrailingZeros(getSignificand(x)) <= getExponent(x));
+  }
+
+  /**
+   * Returns {@code n!}, that is, the product of the first {@code n} positive
+   * integers, {@code 1} if {@code n == 0}, or e n!}, or
+   * {@link Double#POSITIVE_INFINITY} if {@code n! > Double.MAX_VALUE}.
+   *
+   * <p>The result is within 1 ulp of the true value.
+   *
+   * @throws IllegalArgumentException if {@code n < 0}
+   */
+  public static double factorial(int n) {
+    checkNonNegative("n", n);
+    if (n > MAX_FACTORIAL) {
+      return Double.POSITIVE_INFINITY;
+    } else {
+      // Multiplying the last (n & 0xf) values into their own accumulator gives a more accurate
+      // result than multiplying by EVERY_SIXTEENTH_FACTORIAL[n >> 4] directly.
+      double accum = 1.0;
+      for (int i = 1 + (n & ~0xf); i <= n; i++) {
+        accum *= i;
+      }
+      return accum * EVERY_SIXTEENTH_FACTORIAL[n >> 4];
+    }
+  }
+
+  @VisibleForTesting
+  static final int MAX_FACTORIAL = 170;
+
+  @VisibleForTesting
+  static final double[] EVERY_SIXTEENTH_FACTORIAL = {
+      0x1.0p0,
+      0x1.30777758p44,
+      0x1.956ad0aae33a4p117,
+      0x1.ee69a78d72cb6p202,
+      0x1.fe478ee34844ap295,
+      0x1.c619094edabffp394,
+      0x1.3638dd7bd6347p498,
+      0x1.7cac197cfe503p605,
+      0x1.1e5dfc140e1e5p716,
+      0x1.8ce85fadb707ep829,
+      0x1.95d5f3d928edep945};
+
+  /**
+   * Returns {@code true} if {@code a} and {@code b} are within {@code tolerance} of each other.
+   *
+   * <p>Technically speaking, this is equivalent to
+   * {@code Math.abs(a - b) <= tolerance || Double.valueOf(a).equals(Double.valueOf(b))}.
+   *
+   * <p>Notable special cases include:
+   * <ul>
+   * <li>All NaNs are fuzzily equal.
+   * <li>If {@code a == b}, then {@code a} and {@code b} are always fuzzily equal.
+   * <li>Positive and negative zero are always fuzzily equal.
+   * <li>If {@code tolerance} is zero, and neither {@code a} nor {@code b} is NaN, then
+   * {@code a} and {@code b} are fuzzily equal if and only if {@code a == b}.
+   * <li>With {@link Double#POSITIVE_INFINITY} tolerance, all non-NaN values are fuzzily equal.
+   * <li>With finite tolerance, {@code Double.POSITIVE_INFINITY} and {@code
+   * Double.NEGATIVE_INFINITY} are fuzzily equal only to themselves.
+   * </li>
+   *
+   * <p>This is reflexive and symmetric, but <em>not</em> transitive, so it is <em>not</em> an
+   * equivalence relation and <em>not</em> suitable for use in {@link Object#equals}
+   * implementations.
+   *
+   * @throws IllegalArgumentException if {@code tolerance} is {@code < 0} or NaN
+   * @since 13.0
+   */
+  @Beta
+  public static boolean fuzzyEquals(double a, double b, double tolerance) {
+    MathPreconditions.checkNonNegative("tolerance", tolerance);
+    return
+          Math.copySign(a - b, 1.0) <= tolerance
+           // copySign(x, 1.0) is a branch-free version of abs(x), but with different NaN semantics
+          || (a == b) // needed to ensure that infinities equal themselves
+          || ((a != a) && (b != b)); // x != x is equivalent to Double.isNaN(x), but faster
+  }
+
+  /**
+   * Compares {@code a} and {@code b} "fuzzily," with a tolerance for nearly-equal values.
+   *
+   * <p>This method is equivalent to
+   * {@code fuzzyEquals(a, b, tolerance) ? 0 : Double.compare(a, b)}. In particular, like
+   * {@link Double#compare(double, double)}, it treats all NaN values as equal and greater than all
+   * other values (including {@link Double#POSITIVE_INFINITY}).
+   *
+   * <p>This is <em>not</em> a total ordering and is <em>not</em> suitable for use in
+   * {@link Comparable#compareTo} implementations.  In particular, it is not transitive.
+   *
+   * @throws IllegalArgumentException if {@code tolerance} is {@code < 0} or NaN
+   * @since 13.0
+   */
+  @Beta
+  public static int fuzzyCompare(double a, double b, double tolerance) {
+    if (fuzzyEquals(a, b, tolerance)) {
+      return 0;
+    } else if (a < b) {
+      return -1;
+    } else if (a > b) {
+      return 1;
+    } else {
+      return Booleans.compare(Double.isNaN(a), Double.isNaN(b));
+    }
+  }
+
+  private DoubleMath() {}
+}