On Fri, Feb 14, 2003 at 07:15:04PM -0500, rif wrote:
> In order to get good performance, will I have to make a single
> function that takes the whole vector and does all the operations
> internally (i.e., a function called square-vector for instance), or
> can I build a higher-order function which takes a procedure like
> square and operates on the elements of the vector? It seems that if
> I'm guaranteed to lose as soon as I call a function with a
> double-float argument, that it's going to be hard to do this fast.
> What're good strategies here?
Perhaps judicious use of inlined functions and macros (possibly
compiler macros, if you still want to have function-like behaviour
under some circumstances...)? E.g.:
(declaim (inline square-df))
(defun square-df (x)
(declare (optimize (speed 3) (safety 0) (debug 0))
(double-float x))
(* x x))
(deftype df->df-func () `(function (double-float) double-float))
(deftype df-vector () `(simple-array double-float 1))
(defmacro %nmap-df-vector (func df-vector)
(let (($func (gensym "FUNC"))
($df-vector (gensym "DF-VECTOR"))
($index (gensym "INDEX")))
`(let ((,$func ,func)
(,$df-vector ,df-vector))
(declare (type df-vector ,$df-vector)
(type df->df-func ,$func))
(loop for ,$index of-type fixnum from 0 below (length ,$df-vector)
do (setf (aref ,$df-vector ,$index)
(funcall ,$func (aref ,$df-vector ,$index)))))))
(define-compiler-macro nmap-df-vector (func df-vector)
`(%nmap-df-vector ,func ,df-vector))
(defun nmap-df-vector (func df-vector)
(%nmap-df-vector func df-vector))
(defvar *vector* (make-array (list 4096) :element-type 'double-float))
;; Runs in 0.32 seconds, 0 bytes consed
(defun test-1 ()
(declare (optimize (speed 3) (safety 0) (debug 0)))
(dotimes (i 30000)
(nmap-df-vector #'square-df *vector*)))
;; Runs in 64.33 seconds with 3.64 gigabytes consed
(defun test-2 ()
(declare (optimize (speed 3) (safety 0) (debug 0)))
(dotimes (i 30000)
(funcall #'nmap-df-vector #'square-df *vector*)))
