88 lines
2.5 KiB
C++
88 lines
2.5 KiB
C++
#include "cpuTime.H"
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#include "Pair.H"
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#include "randomGenerator.H"
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using namespace Foam;
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//- Number of calculations to do. Need 10^8-ish to get enough time (~2 seconds)
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// to meaningfully compare.
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static const label n = 100000000;
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//- Range of exponents to calculate. From -E to +E. Zero will be omitted so
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// that we can do roots, too. At small values (<8) integer powers win. At
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// larger values (>16), scalar powers do better.
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static const label E = 4;
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//- Run a given power method
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template<class Pow>
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Pair<scalar> run(Pow pow)
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{
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randomGenerator rndGen(0);
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cpuTime time;
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scalar y = 0;
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for (label i = 0; i < n; ++ i)
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{
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const scalar x = rndGen.sampleAB<scalar>(rootSmall, rootGreat);
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const label e =
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rndGen.sample01<label>()
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? rndGen.sampleAB<label>(- E, 0)
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: rndGen.sampleAB<label>(1, E + 1);
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y = y*scalar(i)/(i + 1) + pow(x, e)/(i + 1);
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}
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return Pair<scalar>(y, time.cpuTimeIncrement());
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}
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//- Scalar power function
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scalar scalarPow(const scalar x, const scalar e)
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{
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return Foam::pow(x, e);
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}
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//- Scalar root function
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scalar scalarRoot(const scalar x, const scalar e)
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{
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return Foam::pow(x, 1/e);
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}
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//- Run tests
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int main()
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{
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Info<< "Averaging " << n << " power/root calculations with exponents "
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<< "ranging from " << - E << " to " << + E << ":" << endl;
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Info<< incrIndent;
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Info<< indent << " Scalar power: " << flush;
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const Pair<scalar> scalarPowYTime =
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run(static_cast<scalar (*)(scalar, scalar)>(&scalarPow));
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Info<< "Calculated value " << scalarPowYTime.first()
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<< " in " << scalarPowYTime.second() << " s" << endl;
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Info<< indent << " Integer power: " << flush;
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const Pair<scalar> integerPowYTime =
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run(static_cast<scalar (*)(scalar, label)>(&integerPow));
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Info<< "Calculated value " << integerPowYTime.first()
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<< " in " << integerPowYTime.second() << " s" << endl;
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Info<< indent << " Scalar root: " << flush;
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const Pair<scalar> scalarRootYTime =
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run(static_cast<scalar (*)(scalar, scalar)>(&scalarRoot));
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Info<< "Calculated value " << scalarRootYTime.first()
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<< " in " << scalarRootYTime.second() << " s" << endl;
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Info<< indent << " Integer root: " << flush;
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const Pair<scalar> integerRootYTime =
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run(static_cast<scalar (*)(scalar, label)>(&integerRoot));
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Info<< "Calculated value " << integerRootYTime.first()
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<< " in " << integerRootYTime.second() << " s" << endl;
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Info<< decrIndent;
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return 0;
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}
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