Function pow

deps/opencv/modules/core/src/mathfuncs.cpp:1892–1989

void pow( InputArray _src, double power, OutputArray _dst )
{
    Mat src = _src.getMat();
    int type = src.type(), depth = src.depth(), cn = src.channels();

    _dst.create( src.dims, src.size, type );
    Mat dst = _dst.getMat();

    int ipower = cvRound(power);
    bool is_ipower = false;

    if( fabs(ipower - power) < DBL_EPSILON )
    {
        if( ipower < 0 )
        {
            divide( 1., src, dst );
            if( ipower == -1 )
                return;
            ipower = -ipower;
            src = dst;
        }

        switch( ipower )
        {
        case 0:
            dst = Scalar::all(1);
            return;
        case 1:
            src.copyTo(dst);
            return;
        case 2:
            multiply(src, src, dst);
            return;
        default:
            is_ipower = true;
        }
    }
    else
        CV_Assert( depth == CV_32F || depth == CV_64F );

    const Mat* arrays[] = {&src, &dst, 0};
    uchar* ptrs[2];
    NAryMatIterator it(arrays, ptrs);
    int len = (int)(it.size*cn);

    if( is_ipower )
    {
        IPowFunc func = ipowTab[depth];
        CV_Assert( func != 0 );

        for( size_t i = 0; i < it.nplanes; i++, ++it )
            func( ptrs[0], ptrs[1], len, ipower );
    }
    else if( fabs(fabs(power) - 0.5) < DBL_EPSILON )
    {
        MathFunc func = power < 0 ?
            (depth == CV_32F ? (MathFunc)InvSqrt_32f : (MathFunc)InvSqrt_64f) :
            (depth == CV_32F ? (MathFunc)Sqrt_32f : (MathFunc)Sqrt_64f);