LI75817: INCORRECT CALCULATION FOR COMPLEX NUMBER

XL C/C++ for Linux Fix Pack 9 (August 2013 Update) for 11.1
April 2011 Update for XL C/C++ for Linux, V11.1
July 2011 Update for XL C/C++ for Linux, V11.1
October 2011 Update for XL C/C++ for Linux, V11.1
June 2012 Update for XL C/C++ for Linux, V11.1
October 2012 Update for XL C/C++ for Linux, V11.1
XL C/C++ for Linux Fix Pack 8 (June 2013 Update) for 11.1

APAR status

• Closed as program error.

Error description

• When dividing a complex number by one, an incorrect real number
  is observed and a core is generated.
  
  This occurs when compiling the below test case with any of the
  following options:
  
  " -qsmp=omp"
  " -qsmp=omp -qinline=level=5"
  
  ==== Test Case:
  test.cpp:
  #include <iostream>
  #include <complex>
  
  using namespace std;
  
  int main()
  {
     complex<double> ddd;
     ddd = 1.0;
  
  #pragma omp parallel for
     for ( int i=0; i<4; ++i )
     {
        complex<double> csum;
  
        csum = 2.0 / ddd;
  
  #pragma omp critical
        clog << csum << " <- expected:  (2,0)" << endl;
     }
  }
  ==========
  
  ==== Actual Output:
  # xlC_r -qsmp=omp test.cpp && ./a.out
  (-1.78686e-308,-0) <- expected:  (2,0)
  (-1.78686e-308,-0) <- expected:  (2,0)
  Segmentation fault (core dumped)
  #
  

Local fix

• Use '-qsmp=omp -qinline=level=4'.
  

Problem summary

• PROBLEM DESCRIPTION:
  Incorrect calculation of complex number with -O3 -qhot.
  
  USERS AFFECTED:
  Users of at levels -O3 -qhot and higher.
  

Problem conclusion

• In an outlined procedure the real and complex members of a
  complex number were not privatized into that procedure but the
  owner was. So the stores into them did not go into the location
  of the owner causing runtime failures when the owner was
  referenced. The fix ensures that the owner and its members will
  become local to the outlined procedure.
  

Temporary fix

Comments

APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

  IZ96359

Fix information

• Fixed component name

  XL C/C++ FOR LI

• Fixed component ID

  5724X1400

Applicable component levels

• RB10 PSY

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