go /
exp /
1f324b6b2dcc90f2fb09a94cac109ba3495d39c9 x/exp/rand: new rand package
This is an approximately compatible new implementation of math/rand.
The differences are:
Source emits uint64s rather than positive int64s.
The method is now
Uint64() uint64; not
Int63() int64
There are corresponding new methods on Rand:
func (r *Rand) Uint64() uint64
func (r *Rand) Uint64n(n uint64) uint64
The default Source is now an exported type, PCGSource.
The default Source holds 128 bits of state for a 64-bit
result. This has good statistical properties but is slower,
largely because the multiplication step is inefficient.
That can be improved with assembler.
Thus the default Source has a two 64-bit words of state (in
math/rand it has 607 words). It is thus practical to have
millions of Sources in the address space, making it well
suited to lock-free simulations using random numbers.
Benchmarks:
benchmark old ns/op new ns/op delta
BenchmarkInt63Threadsafe-4 20.0 24.4 +22.00%
BenchmarkInt63Unthreadsafe-4 6.32 13.0 +105.70%
BenchmarkIntn1000-4 16.4 23.8 +45.12%
BenchmarkInt63n1000-4 25.5 23.8 -6.67%
BenchmarkInt31n1000-4 14.2 23.8 +67.61%
BenchmarkFloat32-4 11.8 21.0 +77.97%
BenchmarkFloat64-4 8.76 18.3 +108.90%
BenchmarkPerm3-4 80.3 94.3 +17.43%
BenchmarkPerm30-4 627 814 +29.82%
The new generator is PCG XSL RR 128/64 (LCG) from
http://www.pcg-random.org/pdf/toms-oneill-pcg-family-v1.02.pdf
It has been tested against the C version and generates the same
output if initialized to the same value.
See also http://www.pcg-random.org/.
TODO: Improve performance, make initialization better.
Independently, this fixes a bug in the bias-prevention code that
appears, in this package, in Uint64n.
This also exports LockedSource:
Update golang/go#21393.
Change-Id: I48a410fade5d78b8ec993cc1210b96b7a9ab462f
Reviewed-on: https://go-review.googlesource.com/10161
Reviewed-by: Rob Pike <r@golang.org>
11 files changed
