[exikyut]

Oh, okay, my bad!

And wow, fibonacci using hand-rolled AVX :) that would definitely be a sight to see.

...although, I should explicitly point out, AVX is a set of vector streaming/processing instructions. Fibonacci is inherently a single-step operation, with no lookahead.

Okay, so I googled "fibonacci avx". The results were quite a mess but some careful wading found me http://www.insideloop.io/blog/2014/10/14/arrays-part-iii-vec..., which states: "A a consequence, the following code that computes the sequence of Fibonacci can’t get vectorized."

So, forgive my own (bullish!) naivete. AVX, and _possibly_ SIMD, SSE, etc _may not_ be applicable to/usable for Fibonacci computation.

[userbinator]

Vector instructions are certainly usable for scalar computation, although it doesn't make much sense --- you basically just use one piece of one vector and throw away all the other results.

Fibonacci is a toy example but illustrates where the vector instructions do become useful: if you want to compute the n'th term of various Fibonacci-like sequences with different starting conditions but the same recurrence, then you could do them in parallel using those instructions.

[leghifla]

Unrolling the computation of the series, it is possible to compute f(n) using only f(n-4) and f(n-8):

f(n) = 7*f(n-4)-f(n-8)

So, using 4-vector operations, you can compute 4 numbers in one step.