diff --git a/applications/test/Random/Test-Random.C b/applications/test/Random/Test-Random.C index b4bd2f25522fb8579fb2114cef856967d33ac83e..a724fe835770d781b5ff56f9555f2299832f370d 100644 --- a/applications/test/Random/Test-Random.C +++ b/applications/test/Random/Test-Random.C @@ -174,7 +174,21 @@ int main(int argc, char *argv[]) } } - cout<< nl << "Done." << endl; + // Test uniformity of random + { + List<label> samples(20, Zero); + + Random rnd(123456); + for (label i=0; i < 1000*samples.size(); ++i) + { + ++samples[rnd.position<label>(0,19)]; + } + + Info<< nl << "uniform [0,20)" << nl << " " + << flatOutput(samples) << nl; + } + + Info<< nl << "Done." << endl; return 0; } diff --git a/src/OpenFOAM/primitives/random/Random/Random.C b/src/OpenFOAM/primitives/random/Random/Random.C index 307fcb0eb1b0d42e5644d1780f638c1b14b41deb..ed09267b126e677d16575747219bc922c2c80a3a 100644 --- a/src/OpenFOAM/primitives/random/Random/Random.C +++ b/src/OpenFOAM/primitives/random/Random/Random.C @@ -121,14 +121,16 @@ Foam::scalar Foam::Random::position template<> Foam::label Foam::Random::position(const label& start, const label& end) { - return start + round(scalar01()*(end - start)); + // Extend range from [0, N-1] to (-0.5, N-0.5) to ensure that round() + // results in the same number density at the ends. + return start + round(scalar01()*((end - start) + 0.998) - 0.499); } template<> Foam::scalar Foam::Random::globalSample01() { - scalar value = -GREAT; + scalar value(-GREAT); if (Pstream::master()) { @@ -144,7 +146,7 @@ Foam::scalar Foam::Random::globalSample01() template<> Foam::label Foam::Random::globalSample01() { - label value = labelMin; + label value(labelMin); if (Pstream::master()) { @@ -160,7 +162,7 @@ Foam::label Foam::Random::globalSample01() template<> Foam::scalar Foam::Random::globalGaussNormal() { - scalar value = -GREAT; + scalar value(-GREAT); if (Pstream::master()) { @@ -176,16 +178,16 @@ Foam::scalar Foam::Random::globalGaussNormal() template<> Foam::label Foam::Random::globalGaussNormal() { - scalar value = -GREAT; + label value(labelMin); if (Pstream::master()) { - value = GaussNormal<scalar>(); + value = GaussNormal<label>(); } Pstream::scatter(value); - return round(value); + return value; } @@ -196,16 +198,16 @@ Foam::scalar Foam::Random::globalPosition const scalar& end ) { - scalar value = -GREAT; + scalar value(-GREAT); if (Pstream::master()) { - value = scalar01()*(end - start); + value = position<scalar>(start, end); } Pstream::scatter(value); - return start + value; + return value; } @@ -216,16 +218,16 @@ Foam::label Foam::Random::globalPosition const label& end ) { - label value = labelMin; + label value(labelMin); if (Pstream::master()) { - value = round(scalar01()*(end - start)); + value = position<label>(start, end); } Pstream::scatter(value); - return start + value; + return value; }