MultithreadCorner/Hydra: Hydra 3.1.0

Hydra 3.1.0

This release substantially expands the set of pseudorandom number generators available in Hydra. From Random123 (see: John K. Salmon and others, (2011) "Parallel random numbers: as easy as 1, 2, 3". https://dl.acm.org/doi/10.1145/2063384.2063405), Hydra provides wrappers and implementations for

1) Philox 2) Ars 3) Threefry

Squares PRNG ( see: Widynski, Bernard (2020). "Squares: A Fast Counter-Based RNG". https://arxiv.org/abs/2004.06278v2 ), are available from now, in two versions:

1) Squares3 2) Squares4

All the new generators belong to the count-based family, have excellent statistical properties, passing BigCrush (TestU01) and other tests easily, without any failure. All implementations provide very long periods (2^64 -1 or higher). For Squares{3,4}, users get a set of 2500 precalculated seeds for generation of sequences (streams) without statistical artifacts among them (all credits to Bernard Widynski!).

In summary, Squares3, Squares4 and Philox are way faster then the any option available in the previous releases. Ars and Threefry are competitive, being most of the time slightly faster.

From this release, the default PRNG in Hydra is set to hydra::squares3.

General

• Bug fixed in hydra::unweight implementation.
• Other minor fixes and modifications across the tree.