km3_toa_utils.cc

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/*
 * km3_toa_utils.cpp
 *
 *  Created on: 03/mar/2015
 *      \author  Carlo A. Nicolau
 */

#include "km3_toa_utils.hpp"

namespace KM3 {
namespace TOALIB {

void vectorMultiply(complex_type* _vectorSrcA, complex_type* _vectorSrcB, complex_type* _vectorDest, size_t _length)
{

        // TODO: there is space for optimization
        // for instance: how do we manage denormals?
        // do we use SSE/2?
        // so: search for a ready-to-use lib and use it

        /*
         * given two complex numbers: a = a_real + j*a_imag, b = b_real + j*b_imag
         * the product c = a*b can be calculated as:
         * c = (d1-d2) + j*(d1+d3)
         * with:
         * d1 = a_real*(b_real+b_imag)
         * d2 = b_imag*(a_real+b_real)
         * d3 = b_real*(a_imag-a_real)
         *
         * see: http://www.embedded.com/design/real-time-and-performance/4007256/Digital-Signal-Processing-Tricks--Fast-multiplication-of-complex-numbers
         */

        real_type a_real, b_real, a_imag, b_imag;
        real_type k1, k2, k3;
        for(unsigned int k = 0; k < _length; k++) {
                a_real = _vectorSrcA[k][0];
                a_imag = _vectorSrcA[k][1];
                b_real = _vectorSrcB[k][0];
                b_imag = _vectorSrcB[k][1];

                k1 = a_real*(b_real+b_imag);
                k2 = b_imag*(a_real+a_imag);
                k3 = b_real*(a_imag-a_real);

                _vectorDest[k][0] = k1-k2;
                _vectorDest[k][1] = k1+k3;
        }

}

} /* namespace TOALIB */
} /* namespace KM3 */