Hello!
I'm trying to compute the sign() matrix (vector in this case) that is similar to GLSL's sign() https://www.khronos.org/registry/OpenGL-Refpages/gl4/html/sign.xhtml
The main difference is in the behavior of when the input is 0. GLSL returns 1 and cwiseSign returns 0. I've found two propose methods of replicating this behavior in Eigen:

Using select:

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(vector.array() >= 0.0f).select(1.0f, -1.0f)

Using unary expressions:

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vector.unaryExpr([](float in) {return in < 0 ? -1 : 1; });

What would be the most efficient way to achieve this?

Thanks!

Wanted to loop back on this. After some investigation, it looks like the most efficient way I could find was to use the unaryExpr with std::copysignf()

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vector.unaryExpr([](float in) {return std::copysignf(1.0f,in);});

This, for Vector4fs translates to only 6 SSE instructions:
https://godbolt.org/z/6q15ddTE1