(2.4) Fix mulSpectrums inplace #7819
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zchrissirhcz
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So, the key for inplace checking and avoid compiler optimization, is to check two Mat's data, instead of two InputArray/OutputArray's obj?
i.e. the follwing approaches, which is correct?
void som_function(InputArray _src, OutputArray _dst)
{
Mat src = _src.getMat( );
Mat dst = _dst.getMat( );
// check approach 1
if ( _src.getObj( ) == _dst.getObj( ) ) {
_src.copyTo(src);
}
// check approach 2
if ( src.data == dst.data ) {
_src.copyTo(src);
}
}| // correct inplace support | ||
| // Case 'dst.data == srcA.data' is handled by implementation, | ||
| // because it is used frequently (filter2D, matchTemplate) | ||
| if (dst.data == srcB.data) |
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dst is a new created Mat, would dst.data equal to srcB.data? Since srcB = _srcB.getMat, and _srcB is passing from external calling, I don't think if (dst.data == srcB.data) is necessary.
@alalek
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dst is a new created Mat
.create() do not reallocate buffer if requested size is the same. Some problems come from this behavior.
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(Review this pull from cvtColor performance issue in #6760 ) |
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Compiler optimizer might reorder instructions for statements like these:
In case of mixed read/write instructions result becomes wrong.