Hi there!

I was spelunking through the guile source tree and found (rnrs base). The vector-map and vector-for-each in there are horribly inefficient. They are doing (list->vector (apply map PROC (map vector->list vectors))), which means it spends quite some time checking for circular references.

This fixes that. The speedup is surprisingly small, considering we pass through the elements 2 fewer times and don't chase pointers through memory trying to find cycles. Anywhere from 30 to 300% depending on how the stars are aligned on things like (vector-map + vec vec)

One potential speedup we could do is using eq? to compare numbers, but I don't know how well fixnums in guile overlap size_t, regardless of how realistic such a limitation would be. If I change the behaviour of vector-map to go back-to-front (order is unspecified in r6rs) we can easily do (eq? -1 index) as a stop condition to avoid any eventual overhead of type checking with =. (If those are not elided, which I suspect might be the case. ). I did not look at that, since I have too little computer time these days.

As an added bonus, this speeds up quicksort.scm in ecraven's benchmarks by a little.
-- 
  Linus Björnstam