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; vectormap.scm - 
; vector mapping functions

; the supposedly slower one is actually faster

;(time-apply proc arg-list) invokes the procedure proc with the arguments in arg-list. Four ;values are returned: a list containing the result(s) of applying thunk, the number of ;milliseconds of CPU time required to obtain this result, the number of ``real'' milliseconds ;required for the result, and the number of milliseconds of CPU time (included in the second ;result) spent on garbage collection.

    ;;; The fast version
    (define vmap-1
      (lambda (proc v)
        (let ((len (vector-length v)))
          (let ((new-v (make-vector len)))
            (let lp ((i 0))
              (if (= i len)
                  new-v
                  (begin
                    (vector-set! new-v i (proc (vector-ref v i)))
                    (lp (+ i 1)))))))))
    
    ;;;; Slower and simpler...
    (define vmap 
      (lambda (proc v) 
        (list->vector 
          (map proc (vector->list v)))))

(define (range from to)
   (if (> from to) 
       '()
       (cons from (range (+ from 1) to))))

(define (do-times n proc)
   (for-each proc
      (range 1 n)))

;(do-times 100 (lambda (x) (display (format "~A," x))))

(define (do-times-timed n proc) 
   (define-values (results cputime realtime garbagetime) 
     (time-apply  (lambda () (do-times n proc)) '()))
   (display (format "~% ~A ~A ~A" 
      (exact->inexact (/ cputime n)) 
      (exact->inexact (/ realtime n)) 
      (exact->inexact (/ garbagetime n)) )))

;-----------------------------------------------------------------------
(define long-vector (eval (cons 'vector (range 1 1000))))

; supposedly faster one:
(do-times-timed 10000 (lambda (y) (vmap-1 (lambda (x) (* 2 x)) long-vector))) 
;9.771 9.771 0.0

; supposedly slower one:
(do-times-timed 10000 (lambda (y) (vmap (lambda (x) (* 2 x)) long-vector)))
;4.268 4.268 0.0
;-----------------------------------------------------------------------
; multiply a vector by a scalar 
;(define args-list '())
;(define long-vector (eval (cons 'vector (range 1 1000))))
;(define-values (results cputime realtime garbagetime) 
;  (time-apply  (lambda () (vmap-1 (lambda (x) (* 2 x)) long-vector)) args-list))
;(display (format "~%~A, ~A, ~A" cputime realtime garbagetime))