optimize code

modules/core/src/mathfuncs.cpp

@@ -2532,29 +2532,29 @@ double cv::solvePoly( InputArray _coeffs0, OutputArray _roots0, int maxIters )
                 for( j = 0; j < square_root_times; j++)
                 {
                     num.re = old_num_re*old_num_re + old_num_im*old_num_im;
-                    num.re = std::sqrt(num.re);
+                    num.re = sqrt(num.re);
                     num.re += old_num_re;
                     num.im = num.re - old_num_re;
                     num.re /= 2;
-                    num.re = std::sqrt(num.re);
+                    num.re = sqrt(num.re);
 
                     num.im /= 2;
-                    num.im = std::sqrt(num.im);
+                    num.im = sqrt(num.im);
                     if( old_num_re < 0 ) num.im = -num.im;
                 }
 
                 if( num_same_root % 2 != 0){
                     Mat cube_coefs(4, 1, CV_64FC1);
                     Mat cube_roots(3, 1, CV_64FC2);
-                    cube_coefs.at<double>(3) = -(std::pow(old_num_re, 3));
-                    cube_coefs.at<double>(2) = -(15*std::pow(old_num_re, 2) + 27*std::pow(old_num_im, 2));
+                    cube_coefs.at<double>(3) = -(pow(old_num_re, 3));
+                    cube_coefs.at<double>(2) = -(15*pow(old_num_re, 2) + 27*pow(old_num_im, 2));
                     cube_coefs.at<double>(1) = -48*old_num_re;
                     cube_coefs.at<double>(0) = 64;
-                    cv::solveCubic(cube_coefs, cube_roots);
+                    solveCubic(cube_coefs, cube_roots);
 
-                    num.re = std::pow(std::abs(cube_roots.at<double>(0)), 1/3);
-                    if(cube_roots.at<double>(0) < 0) num.re = -num.re;
-                    num.im = std::sqrt(std::pow(num.re, 2) / 3 - old_num_re / (3*num.re));
+                    if(cube_roots.at<double>(0) >= 0) num.re = pow(cube_roots.at<double>(0), 1./3);
+                    else num.re = -pow(-cube_roots.at<double>(0), 1./3);
+                    num.im = sqrt(pow(num.re, 2) / 3 - old_num_re / (3*num.re));
                 }
             }