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src.it.unimi.dsi.util.package-info Maven / Gradle / Ivy

/**
 * 
Miscellaneaous utility classes.
 *
 * 
Pseudorandom number generators
 *
 * 
We provide a number of fast, high-quality PRNGs with different features. You can get detailed
 * information about the generators at our PRNG page, together
 * with a reasoned guide to the choice of the generator that's right for you.
 *
 * 
A table summarizing timings is provided below. The timings were measured on an
 * Intel® Core™ i7-7700 CPU @ 3.60GHz (Kaby Lake),
 * and they are now obtained by means of
 * JMH microbenchmarks. The JMH timings were decreased by 1ns, as
 * using the low-level {@code perfasm} profiler the JMH overhead was estimated at ≈1ns per call.
 *
 * 

 * 

 * 
{@link java.util.Random Random}
 * 
{@link java.util.concurrent.ThreadLocalRandom ThreadLocalRandom}
 * 
{@link java.util.SplittableRandom SplittableRandom}
 * 
{@link it.unimi.dsi.util.SplitMix64RandomGenerator SplitMix64}
 * 
{@link it.unimi.dsi.util.XoRoShiRo128StarStarRandom xoroshiro128**}
 * 
{@link it.unimi.dsi.util.XoRoShiRo128PlusRandom xoroshiro128+}
 * 
{@link it.unimi.dsi.util.XoShiRo256StarStarRandom xoshiro256**}
 * 
{@link it.unimi.dsi.util.XoShiRo256PlusRandom xoshiro256+}
 * 
{@link it.unimi.dsi.util.XorShift1024StarPhiRandom xorshift1024*φ}
 *
 * 
nextLong()                                 
15.825
1.450
1.482
1.553
1.850
1.524
2.135
1.876
2.157
 * 
nextInt(100000)                            
7.391
2.400
2.805
2.858
2.933
2.407
3.266
2.754
3.509
 * 
nextDouble()                               
15.825
2.125
2.434
2.453
2.503
2.105
2.802
2.382
3.077
 * 
 *
 * 
Note that generators that are extremely fast in C, such as xoshiro256+, do not perform particularly well in Java, most likely
 * because of the cost of accessing variables, which rises as the size of the state space grows.
 *
 * 
For each generator, we provide a version that extends {@link java.util.Random}, overriding (as usual) the {@link java.util.Random#next(int) next(int)} method. Nonetheless,
 * since the generators are all inherently 64-bit also {@link java.util.Random#nextInt() nextInt()}, {@link java.util.Random#nextFloat() nextFloat()},
 * {@link java.util.Random#nextLong() nextLong()}, {@link java.util.Random#nextDouble() nextDouble()}, {@link java.util.Random#nextBoolean() nextBoolean()}
 * and {@link java.util.Random#nextBytes(byte[]) nextBytes(byte[])} have been overridden for speed (preserving, of course, {@link java.util.Random}'s semantics).
 *
 * 
If you do not need an instance of {@link java.util.Random}, or if you need a {@link org.apache.commons.math3.random.RandomGenerator} to use
 * with Commons Math, there is for each generator a corresponding {@link org.apache.commons.math3.random.RandomGenerator RandomGenerator}
 * implementation, which indeed we suggest to use in general if you do not need a generator implementing {@link java.util.Random}.
 */

package it.unimi.dsi.util;