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testRandom.cpp

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#include <testRandom.h>
#include <ImathRandom.h>
#include <ImathVec.h>
#include <ImathFun.h>
#include <iostream>
#include <iomanip>
#include <assert.h>


using namespace std;
using Imath::abs;

namespace {


template <class Rand>
void
testGenerator ()
{
    //
    // Test if the values, and the differences between
    // successive values, are evenly distributed.
    //

    const int N = 10;
    const int M = 100000;

    int values[N + 1];
    int diffs[2 * N + 3];
    int *v = &values[0];
    int *d = &diffs[N + 2];

    for (int i = 0; i <= N; ++i)
      v[i] = 0;

    for (int i = -N; i <= N; ++i)
      d[i] = 0;

    Rand rand (0);
    float previous = 0;

    for (int i = 0; i < M * N; ++i)
    {
      float r = rand.nextf (0.0, 1.0);
      float diff = r - previous;
      previous = r;

      v[int (r * N)] += 1;
      d[Imath::floor (diff * N + 0.5)] += 1;
    }

    cout << "  values" << endl;

    for (int i = 0; i < N; ++i)
    {
      // cout << setw (4) << i << ' ' << setw(6) << v[i] << ' ';
      assert (abs (v[i] - M) < 0.01 * M);

      // for (int j = 0; j < v[i] * 60 / M; ++j)
      //     cout << '*';

      // cout << endl;
    }

    assert (v[N] == 0);

    cout << "  differences between successive values" << endl;

    for (int i = -N; i <= N; ++i)
    {
      // cout << setw (4) << i << ' ' << setw (6) << d[i] << ' ';
      assert (abs ((N - abs (i)) * M / N - d[i]) < 0.05 * M);

      // for (int j = 0; j < d[i] * 60 / M; ++j)
      //     cout << '*';

      // cout << endl;
    }
}


template <class Rand>
void
testSolidSphere ()
{
    const int N = 10;
    const int M = 10000;
    int v[N + 1];

    for (int i = 0; i <= N; ++i)
      v[i] = 0;

    Rand rand (0);

    for (int i = 0; i < M * N; ++i)
    {
      Imath::V3f p = Imath::solidSphereRand<Imath::V3f> (rand);
      float l = p.length();
      v[Imath::floor (l * N)] += 1;

      assert (l < 1.00001);
    }

    for (int i = 0; i < N; ++i)
      assert (v[i] > 0);
}


template <class Rand>
void
testHollowSphere ()
{
    const int M = 100000;
    Rand rand (0);

    for (int i = 0; i < M; ++i)
    {
      Imath::V3f p = Imath::hollowSphereRand<Imath::V3f> (rand);
      float l = p.length();

      assert (abs (l - 1) < 0.00001);
    }
}


} // namespace


void
testRandom ()
{
    cout << "Testing random number generators" << endl;

    cout << "Rand32" << endl;
    testGenerator<Imath::Rand32>();

    cout << "Rand48" << endl;
    testGenerator<Imath::Rand32>();

    cout << "solidSphereRand()" << endl;
    testSolidSphere<Imath::Rand32>();

    cout << "hollowSphereRand()" << endl;
    testHollowSphere<Imath::Rand32>();

    cout << "ok\n" << endl;
}

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