update fixing bug #5599

modules/core/src/mathfuncs.cpp

@@ -2530,21 +2530,14 @@ double cv::solvePoly( InputArray _coeffs0, OutputArray _roots0, int maxIters )
                     double old_num_im = num.im;
 
                     num.re = old_num_re*old_num_re + old_num_im*old_num_im;
-                    Mat num_re_arr = (Mat_<double>(1,1) << num.re);
-                    cv::sqrt(num_re_arr, num_re_arr);
-                    num.re = num_re_arr.at<double>(0, 0);
+                    num.re = std::sqrt(num.re);
                     num.re += old_num_re;
                     num.im = num.re - old_num_re;
                     num.re /= 2;
-                    num_re_arr.at<double>(0, 0) = num.re;
-                    cv::sqrt(num_re_arr, num_re_arr);
-                    num.re = num_re_arr.at<double>(0, 0);
+                    num.re = std::sqrt(num.re);
 
-                    Mat num_im_arr = (Mat_<double>(1,1) << num.im);
                     num.im /= 2;
-                    num_im_arr.at<double>(0, 0) = num.re;
-                    cv::sqrt(num_im_arr, num_im_arr);
-                    num.im = num_im_arr.at<double>(0, 0);
+                    num.im = std::sqrt(num.im);
                     if( old_num_re < 0 ) num.im = -num.im;
                 }
             }

samples/cpp/polynominal_equations.cpp

@@ -0,0 +1,38 @@
+ /*
+ * solves equations x^4 - x^2 = 0, and x^2 - 2x + 1 = 0
+ */
+
+#include "opencv2/core/core.hpp"
+#include <iostream>
+
+
+int main(void)
+{
+        cv::Mat coefs = (cv::Mat_<float>(1,5) << 0, 0, -1, 0, 1 );
+        std::cout << "x^4 - x^2 = 0\n\n" << "Coefficients: " << coefs << "\n" << std::endl;
+        cv::Mat r;
+
+        double prec;
+        prec = cv::solvePoly(coefs, r);
+        std::cout << "Preciseness = " << prec << std::endl;
+        std::cout << "roots after 1000 iterations:\n" << r << "\n" << std::endl;
+
+        prec = cv::solvePoly(coefs, r, 9999);
+        std::cout << "Preciseness = " << prec << std::endl;
+        std::cout << "roots after 9999 iterations:\n" << r << "\n" << std::endl;
+
+        std::cout << "\n---------------------------------------\n" << std::endl;
+
+        coefs = (cv::Mat_<float>(1,3) << 1, -2, 1 );
+        std::cout << "x^2 - 2x + 1 = 0\n\n" << "Coefficients: " << coefs << "\n" << std::endl;
+
+        prec = cv::solvePoly(coefs, r);
+        std::cout << "Preciseness = " << prec << std::endl;
+        std::cout << "roots after 1000 iterations:\n" << r << "\n" << std::endl;
+
+        prec = cv::solvePoly(coefs, r, 9999);
+        std::cout << "Preciseness = " << prec << std::endl;
+        std::cout << "roots after 9999 iterations:\n" << r << "\n" << std::endl;
+
+    return 0;
+}