apache / commons-rng / 951

100%

push

travis-ci-com

RNG-174: Improve support for non-zero seeds

Allow specification of a range for array seeds that must be non-zero.

The values for the range are based on the result of
o.a.c.rng.simple.ProvidersCommonParametricTest.testZeroIntArraySeed.

See also the core module for tests using:
- RandomAssert.assertNextIntZeroOutput
- RandomAssert.assertIntArrayConstructorWithSingleBitInPoolIsFunctional

Any generator that fails these tests requires a non-zero seed. In most
cases this was set as the full seed length, or one less for generators
that do not use all the bits of the seed array (WELL_19937_x,
WELL_44497_x).

Notable exceptions:

The KISS generator is reduced to a simple LCG when positions [0, 3) are
all zero. Added a test to demonstrate this. With a zero seed the KISS
LCG passes testZeroIntArraySeed. To avoid a poor generator the seed will
be checked to be non-zero in [0, 3).

The MSWS generator is sensitive to the initial state. Added a test to
show that a zero seed creates zero output. Updating RandomAssert to add
an assertLongArrayConstructorWithSingleBitInPoolIsFunctional test shows
the MSWS fails with single bit seeds. The sub-range has been set to [2,
3) to ensure a non-zero Weyl increment which is the best way to escape a
bad seed. This is a functionally breaking change.

64 of 64 new or added lines in 5 files covered. (100.0%)

4678 of 4693 relevant lines covered (99.68%)

1.0 hits per line