Why are the return values of these doubles -1.#IND?

I have :

double score = cvMatchContourTrees( CT1, CT2, CV_CONTOUR_TREES_MATCH_I1, 0.0 );
        cout<<score<<endl;

There are values returned as -1.#IND. Other than that, the positive values are开发者_如何学Go normal, like 1.34543.

Why does this happen? How do I solve it?

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As Frederic says, it's the result of a 'Not a Number' being formatted by an application built with visual studio on windows. John D Cook has an excellent reference:

Windows displays a NaN as -1.#IND ("IND" for "indeterminate") while Linux displays nan.

...

In short, if you get 1.#INF or inf, look for overflow or division by zero. If you get 1.#IND or nan, look for illegal operations.

Watch out for truncations if you do any sort of formatting with your string; I've encountered related issues when handling these sorts of errors myself.

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std::cout << (0/0.f);
// Output: -1.#IND

It's NaN.

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In my experience -1.#IND comes from imaginary numbers. So, doing cout << sqrt(-1.); should output -1.#IND