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♻️ Extract internal logic of uniformIntDistribution into shared inter…
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49 changes: 49 additions & 0 deletions
49
src/distribution/internals/UniformIntDistributionInternal.ts
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,49 @@ | ||
| import RandomGenerator from '../../generator/RandomGenerator'; | ||
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| /** | ||
| * Uniformly generate number in range [0 ; rangeSize[ | ||
| * @internal | ||
| */ | ||
| export function uniformIntDistributionInternal(rangeSize: number, rng: RandomGenerator): [number, RandomGenerator] { | ||
| const MinRng = rng.min(); | ||
| const NumValues = rng.max() - rng.min() + 1; | ||
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| // Range provided by the RandomGenerator is large enough | ||
| if (rangeSize <= NumValues) { | ||
| let nrng = rng; | ||
| const MaxAllowed = NumValues - (NumValues % rangeSize); | ||
| while (true) { | ||
| const out = nrng.next(); | ||
| const deltaV = out[0] - MinRng; | ||
| nrng = out[1]; | ||
| if (deltaV < MaxAllowed) { | ||
| return [deltaV % rangeSize, nrng]; // Warning: we expect NumValues <= 2**32, so diff too | ||
| } | ||
| } | ||
| } | ||
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| // Compute number of iterations required to have enough random | ||
| // to build uniform entries in the asked range | ||
| let FinalNumValues = NumValues * NumValues; | ||
| let NumIterations = 2; // At least 2 (at this point in the code) | ||
| while (FinalNumValues < rangeSize) { | ||
| FinalNumValues *= NumValues; | ||
| ++NumIterations; | ||
| } | ||
| const MaxAcceptedRandom = rangeSize * Math.floor((1 * FinalNumValues) / rangeSize); | ||
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| let nrng = rng; | ||
| while (true) { | ||
| // Aggregate mutiple calls to next() into a single random value | ||
| let value = 0; | ||
| for (let num = 0; num !== NumIterations; ++num) { | ||
| const out = nrng.next(); | ||
| value = NumValues * value + (out[0] - MinRng); // Warning: we overflow may when diff > max_safe (eg: =max_safe-min_safe+1) | ||
| nrng = out[1]; | ||
| } | ||
| if (value < MaxAcceptedRandom) { | ||
| const inDiff = value - rangeSize * Math.floor((1 * value) / rangeSize); | ||
| return [inDiff, nrng]; | ||
| } | ||
| } | ||
| } |
48 changes: 48 additions & 0 deletions
48
test/unit/distribution/UniformBigIntDistribution.noreg.spec.ts
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,48 @@ | ||
| import { uniformBigIntDistribution } from '../../../src/distribution/UniformBigIntDistribution'; | ||
| import mersenne from '../../../src/generator/MersenneTwister'; | ||
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| const MERSENNE_MIN = mersenne(0).min(); | ||
| const MERSENNE_MAX = mersenne(0).max(); | ||
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| describe('uniformBigIntDistribution [non regression]', () => { | ||
| if (typeof BigInt === 'undefined') { | ||
| it('no test', () => { | ||
| expect(true).toBe(true); | ||
| }); | ||
| return; | ||
| } | ||
| if (typeof BigInt !== 'undefined') { | ||
| it.each` | ||
| from | to | topic | ||
| ${0} | ${2 ** 3 - 1} | ${"range of size divisor of mersenne's one"} | ||
| ${0} | ${2 ** 3 - 2} | ${"range of size divisor of mersenne's one minus one"} | ||
| ${0} | ${2 ** 3} | ${"range of size divisor of mersenne's one plus one"} | ||
| ${48} | ${69} | ${'random range'} | ||
| ${MERSENNE_MIN} | ${MERSENNE_MAX} | ${"mersenne's range"} | ||
| ${MERSENNE_MIN} | ${MERSENNE_MAX - 1} | ${"mersenne's range minus one"} | ||
| ${MERSENNE_MIN} | ${MERSENNE_MAX + 1} | ${"mersenne's range plus one"} | ||
| ${0} | ${2 ** 40 - 1} | ${"range of size multiple of mersenne's one"} | ||
| ${0} | ${2 ** 40 - 2} | ${"range of size multiple of mersenne's one minus one"} | ||
| ${0} | ${2 ** 40} | ${"range of size multiple of mersenne's one plus one"} | ||
| ${Number.MIN_SAFE_INTEGER} | ${Number.MAX_SAFE_INTEGER} | ${'full integer range'} | ||
| `('Should not change its output in range ($from, $to) except for major bumps', ({ from, to }) => { | ||
| // Remark: | ||
| // ======================== | ||
| // This test is purely there to ensure that we do not introduce any regression | ||
| // during a commit without noticing it. | ||
| // The values we expect in the output are just a snapshot taken at a certain time | ||
| // in the past. They might be wrong values with bugs. | ||
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| let rng = mersenne(0); | ||
| const distribution = uniformBigIntDistribution(BigInt(from), BigInt(to)); | ||
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| const values: bigint[] = []; | ||
| for (let idx = 0; idx !== 10; ++idx) { | ||
| const [v, nrng] = distribution(rng); | ||
| values.push(v); | ||
| rng = nrng; | ||
| } | ||
| expect(values).toMatchSnapshot(); | ||
| }); | ||
| } | ||
| }); |
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40 changes: 40 additions & 0 deletions
40
test/unit/distribution/UniformIntDistribution.noreg.spec.ts
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,40 @@ | ||
| import { uniformIntDistribution } from '../../../src/distribution/UniformIntDistribution'; | ||
| import mersenne from '../../../src/generator/MersenneTwister'; | ||
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| const MERSENNE_MIN = mersenne(0).min(); | ||
| const MERSENNE_MAX = mersenne(0).max(); | ||
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| describe('uniformIntDistribution [non regression]', () => { | ||
| it.each` | ||
| from | to | topic | ||
| ${0} | ${2 ** 3 - 1} | ${"range of size divisor of mersenne's one"} | ||
| ${0} | ${2 ** 3 - 2} | ${"range of size divisor of mersenne's one minus one"} | ||
| ${0} | ${2 ** 3} | ${"range of size divisor of mersenne's one plus one"} | ||
| ${48} | ${69} | ${'random range'} | ||
| ${MERSENNE_MIN} | ${MERSENNE_MAX} | ${"mersenne's range"} | ||
| ${MERSENNE_MIN} | ${MERSENNE_MAX - 1} | ${"mersenne's range minus one"} | ||
| ${MERSENNE_MIN} | ${MERSENNE_MAX + 1} | ${"mersenne's range plus one"} | ||
| ${0} | ${2 ** 40 - 1} | ${"range of size multiple of mersenne's one"} | ||
| ${0} | ${2 ** 40 - 2} | ${"range of size multiple of mersenne's one minus one"} | ||
| ${0} | ${2 ** 40} | ${"range of size multiple of mersenne's one plus one"} | ||
| ${Number.MIN_SAFE_INTEGER} | ${Number.MAX_SAFE_INTEGER} | ${'full integer range'} | ||
| `('Should not change its output in range ($from, $to) except for major bumps', ({ from, to }) => { | ||
| // Remark: | ||
| // ======================== | ||
| // This test is purely there to ensure that we do not introduce any regression | ||
| // during a commit without noticing it. | ||
| // The values we expect in the output are just a snapshot taken at a certain time | ||
| // in the past. They might be wrong values with bugs. | ||
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| let rng = mersenne(0); | ||
| const distribution = uniformIntDistribution(from, to); | ||
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| const values: number[] = []; | ||
| for (let idx = 0; idx !== 10; ++idx) { | ||
| const [v, nrng] = distribution(rng); | ||
| values.push(v); | ||
| rng = nrng; | ||
| } | ||
| expect(values).toMatchSnapshot(); | ||
| }); | ||
| }); |
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