I have a __m256d vector packed with four 64-bit floating-point values. I need to find the horizontal maximum of the vector's elements and store the result in a double-precision scalar value; My at...

I have a packed vector of four 64-bit floating-point values. I would like to get the sum of the vector's elements. With SSE (and using 32-bit floats) I could just do the following: v_sum = ...

The v4 series of the gcc compiler can automatically vectorize loops using the SIMD processor on some modern CPUs, such as the AMD Athlon or Intel Pentium/Core chips. How is this done?

Is it better in some sense to vectorize code by hand, using explicit pragmas or to rely on or use auto-vectorization? For optimum performance using auto-vectorization, one would have to monit...