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improved randShuffle as suggested by John Stark in http://code.opencv.org/issues/3730

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This commit is contained in:
Vadim Pisarevsky
2015-05-02 21:31:47 +03:00
parent 96b5ec14d4
commit 9c0b740b84
1 changed files with 16 additions and 10 deletions
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26
modules/core/src/rand.cpp
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@@ -748,29 +748,35 @@ namespace cv
{
template<typename T> static void
randShuffle_( Mat& _arr, RNG& rng, double iterFactor )
randShuffle_( Mat& _arr, RNG& rng, double )
{
int sz = _arr.rows*_arr.cols, iters = cvRound(iterFactor*sz);
unsigned sz = (unsigned)_arr.total();
if( _arr.isContinuous() )
{
T* arr = _arr.ptr<T>();
for( int i = 0; i < iters; i++ )
for( unsigned i = 0; i < sz; i++ )
{
int j = (unsigned)rng % sz, k = (unsigned)rng % sz;
std::swap( arr[j], arr[k] );
unsigned j = (unsigned)rng % sz;
std::swap( arr[j], arr[i] );
}
}
else
{
CV_Assert( _arr.dims <= 2 );
uchar* data = _arr.ptr();
size_t step = _arr.step;
int rows = _arr.rows;
int cols = _arr.cols;
for( int i = 0; i < iters; i++ )
for( int i0 = 0; i0 < rows; i0++ )
{
int j1 = (unsigned)rng % sz, k1 = (unsigned)rng % sz;
int j0 = j1/cols, k0 = k1/cols;
j1 -= j0*cols; k1 -= k0*cols;
std::swap( ((T*)(data + step*j0))[j1], ((T*)(data + step*k0))[k1] );
T* p = _arr.ptr<T>(i0);
for( int j0 = 0; j0 < cols; j0++ )
{
unsigned k1 = (unsigned)rng % sz;
int i1 = (int)(k1 / cols);
int j1 = (int)(k1 - (unsigned)i1*(unsigned)cols);
std::swap( p[j0], ((T*)(data + step*i1))[j1] );
}
}
}
}