I wrote a simple test routine:
for(int i = 0; i < 100;++i) { std::cout<< "i="<< i <<": "; print_complex(lapack_make_complex_double(1,0)); std::cout<< std::endl; }where print_complex prints the complex to console.
The routine will end with an exception:
First-chance exception at 0x00420fd0 in LTELinkLevelSimulator.exe: 0xC0000005: Access violation reading location 0x00000000.
Unhandled exception at 0x770b15de in LTELinkLevelSimulator.exe:0xC0000005: Access violation reading location 0x00000000.
and the printed complexes on the console are:
See, something goes wrong. The complex should be 1+0j, but the lapack_make_complex_double function, which is a C interface to create a complex with double precision, is not stable.
I have to write my own make_complex routine instead. It looks like:
lapack_complex_double make_complex(constdouble a, const double b) { lapack_complex_double c; c.real = a; c.imag = b; return c; }If replace the lapack_make_complex_double with make_complex, the output is:
No error happens again!
One last word, when using the CBLAS and LAPACKE library in your C/C++ code, be very careful of such flaws.