There is something wrong with the norm() in STL to get the norm2 of complex numbers. Suppose we have complex<double> x(8,1), the norm of x should be 8*8 + 1*1 = 65, but norm(x) returns 64, which is incorrect. If we do complex<float> x(8,1), there is no problem, norm(x) does return 65. The issue is not limited to version 4.2.1. It is observed in other versions as well.

This works for me. Please provide a testcase that fails.

I used: #include <complex> #include <algorithm> #include <iostream> int main() { std::complex<double> x(8, 1); std::cout << std::norm(x) << std::endl; }

Subject: RE: error in norm() of STL I did additional test based your test code. You are right that norm() seems to be fine. The problem happens when I try to cast the return double value of norm() to unsigned long long (please see my test code below and the corresponding output). Still, it bothers me that if I carry out the norm calculation explicitly, instead of calling norm(), there is no such an issue. Thanks, - Yongbin My test code: ================================================================= #include <iostream> #include <complex> using namespace std; main() { complex<double> tt(8,1); double x, y; x = norm(tt); double r = tt.real(), i = tt.imag(); y = r*r + i*i; cout << tt << "\t" << (unsigned long long)x << "\t" << (unsigned long long)y << endl; cout << tt << "\t" << x << "\t" << y << endl; } ====================================== The output (8,1) 64 65 (8,1) 65 65 -----Original Message----- From: rguenth at gcc dot gnu dot org [mailto:gcc-bugzilla@gcc.gnu.org] Sent: Wednesday, February 27, 2008 4:44 AM To: Wei, Yongbin Subject: [Bug c++/35389] error in norm() of STL ------- Comment #2 from rguenth at gcc dot gnu dot org 2008-02-27 12:43 ------- I used: #include <complex> #include <algorithm> #include <iostream> int main() { std::complex<double> x(8, 1); std::cout << std::norm(x) << std::endl; }

Subject: Re: error in norm() of STL On Wednesday 27 of February 2008 21:13:13 ywei at qualcomm dot com wrote: > ------- Comment #3 from ywei at qualcomm dot com 2008-02-27 20:13 ------- > Subject: RE: error in norm() of STL > > I did additional test based your test code. You are right that norm() > seems to be fine. The problem happens when I try to cast the return > double value of norm() to unsigned long long (please see my test code > below and the corresponding output). Still, it bothers me that if I > carry out the norm calculation explicitly, instead of calling norm(), > there is no such an issue. > > Thanks, > - Yongbin > > My test code: > ================================================================= > #include <iostream> > #include <complex> > > using namespace std; > > main() { > > complex<double> tt(8,1); > double x, y; > > x = norm(tt); > double r = tt.real(), i = tt.imag(); > y = r*r + i*i; > > cout << tt << "\t" << (unsigned long long)x << "\t" << (unsigned > long long)y << endl; > cout << tt << "\t" << x << "\t" << y << endl; > } > ====================================== > The output > (8,1) 64 65 > (8,1) 65 65 $ ./a.out (8,1) 64 65 (8,1) 64.999999999999985789 65 (long long)64.99999 -> 64.

Created attachment 15239 [details] test.cpp.diff

This is just the non bug with respect of percussion. See http://gcc.gnu.org/bugs.html#nonbugs_general *** This bug has been marked as a duplicate of 323 ***