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8202449: overflow handling in Random.doubles

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Reviewed-by: darcy
This commit is contained in:
Raffaello Giulietti 2022-06-08 16:28:18 +00:00 • committed by Joe Darcy
parent c15e10fb6c
commit c8cff1bd6f
5 changed files with 82 additions and 71 deletions
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41
src/java.base/share/classes/java/util/Random.java
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@ -256,7 +256,8 @@ public class Random implements RandomGenerator, java.io.Serializable {
private static final long addend = 0xBL;
private static final long mask = (1L << 48) - 1;
private static final double DOUBLE_UNIT = 0x1.0p-53; // 1.0 / (1L << 53)
private static final double DOUBLE_UNIT = 0x1.0p-53; // 1.0 / (1L << Double.PRECISION)
private static final float FLOAT_UNIT = 0x1.0p-24f; // 1.0f / (1 << Float.PRECISION)
/**
* Creates a new random number generator. This constructor sets
@ -598,12 +599,12 @@ public class Random implements RandomGenerator, java.io.Serializable {
* low-order bit of the significand would be 0 than that it would be 1.]
*
* @return the next pseudorandom, uniformly distributed {@code float}
* value between {@code 0.0} and {@code 1.0} from this
* value between {@code 0.0f} and {@code 1.0f} from this
* random number generator's sequence
*/
@Override
public float nextFloat() {
return next(24) / ((float)(1 << 24));
return next(Float.PRECISION) * FLOAT_UNIT;
}
/**
@ -644,7 +645,7 @@ public class Random implements RandomGenerator, java.io.Serializable {
*/
@Override
public double nextDouble() {
return (((long)(next(26)) << 27) + next(27)) * DOUBLE_UNIT;
return (((long)(next(Double.PRECISION - 27)) << 27) + next(27)) * DOUBLE_UNIT;
}
private double nextNextGaussian;
@ -1070,26 +1071,12 @@ public class Random implements RandomGenerator, java.io.Serializable {
* pseudorandom {@code double} values, each conforming to the given origin
* (inclusive) and bound (exclusive).
*
* <p>A pseudorandom {@code double} value is generated as if it's the result
* of calling the following method with the origin and bound:
* <pre> {@code
* double nextDouble(double origin, double bound) {
* double r = nextDouble();
* r = r * (bound - origin) + origin;
* if (r >= bound) // correct for rounding
* r = Math.nextDown(bound);
* return r;
* }}</pre>
*
* @param streamSize the number of values to generate
* @param randomNumberOrigin the origin (inclusive) of each random value
* @param randomNumberBound the bound (exclusive) of each random value
* @return a stream of pseudorandom {@code double} values,
* each with the given origin (inclusive) and bound (exclusive)
* @throws IllegalArgumentException if {@code streamSize} is less than zero,
* or {@code randomNumberOrigin} is not finite,
* or {@code randomNumberBound} is not finite, or {@code randomNumberOrigin}
* is greater than or equal to {@code randomNumberBound}
* @throws IllegalArgumentException {@inheritDoc}
* @since 1.8
*/
@Override
@ -1101,18 +1088,7 @@ public class Random implements RandomGenerator, java.io.Serializable {
* Returns an effectively unlimited stream of pseudorandom {@code
* double} values, each conforming to the given origin (inclusive) and bound
* (exclusive).
*
* <p>A pseudorandom {@code double} value is generated as if it's the result
* of calling the following method with the origin and bound:
* <pre> {@code
* double nextDouble(double origin, double bound) {
* double r = nextDouble();
* r = r * (bound - origin) + origin;
* if (r >= bound) // correct for rounding
* r = Math.nextDown(bound);
* return r;
* }}</pre>
*
* @implNote This method is implemented to be equivalent to {@code
* doubles(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
*
@ -1120,8 +1096,7 @@ public class Random implements RandomGenerator, java.io.Serializable {
* @param randomNumberBound the bound (exclusive) of each random value
* @return a stream of pseudorandom {@code double} values,
* each with the given origin (inclusive) and bound (exclusive)
* @throws IllegalArgumentException if {@code randomNumberOrigin}
* is greater than or equal to {@code randomNumberBound}
* @throws IllegalArgumentException {@inheritDoc}
* @since 1.8
*/
@Override