Torquil Macdonald Sørensen <torquil@xxxxxxxxx> writes:
> #include "iostream"
> #include "blitz/array.h"
>
> int main()
> {
> blitz::Array<double,1> X(3); X = 0.0;
>
> blitz::Array<double,1> var(1); var = 0.0;
>
> for(int i = 0; i != 1; ++i) {
> for(int c = 0; c != 3; ++c) X(c) = double(c);
>
> var(i) = 0.0;
> for(int c = 0; c != 3; ++c) var(i) += X(c)*X(c);
> var(i) /= 3.0;
> }
>
> std::cout << var(0) << std::endl;
>
> return(0);
> }
> ---------------------------
>
>
> If I compile with "-O2", it prints 0, which is wrong.
>
> If I compile with "-O2 -fno-strict-aliasing", it prints the correct answer 1.6666..
In every case I've looked at, when code gives the expected answer only
when using -fno-strict-aliasing, it is because the code is using a type
cast in an invalid way.
In this case I would assume that the invalid type cast occurs in the
blitz library code. Look for invalid type casts there.
Ian
