The second is faster because an intermediate list requires more allocation than an intermediate array of values.
(The `call-with-values' expression is compiled to an internal `apply-values' form, so no closure is allocated in that case. Also, `make-prefab-struct' receives its arguments in an internal array in either case.) At Mon, 22 Feb 2010 08:42:08 -0700, Jay McCarthy wrote: > I guess my real question is: should I rely on this or is it a coincidence? > > Jay > > On Mon, Feb 22, 2010 at 8:40 AM, Sam Tobin-Hochstadt <sa...@ccs.neu.edu> > wrote: > > On Mon, Feb 22, 2010 at 10:37 AM, Jay McCarthy <jay.mccar...@gmail.com> > wrote: > >> How should I expect these two lines to compare performance-wise: > >> > >> (apply make-prefab-struct > >> (vector->list v)) > >> > >> vs > >> > >> (call-with-values (lambda () (vector->values v)) > >> make-prefab-struct) > > > > #lang scheme > > > > (define v '#(foo 1 2 3)) > > > > (define k 1000000) > > > > (define (run1) > > (for ((i (in-range k))) > > (apply make-prefab-struct > > (vector->list v)))) > > > > > > (define (run2) > > (for ((i (in-range k))) > > (call-with-values (lambda () (vector->values v)) > > make-prefab-struct))) > > > > (time (run1)) > > (time (run2)) > > > > cpu time: 1068 real time: 1075 gc time: 60 > > cpu time: 864 real time: 866 gc time: 44 > > > > > > > > > > -- > > sam th > > sa...@ccs.neu.edu > > > > > > -- > Jay McCarthy <j...@cs.byu.edu> > Assistant Professor / Brigham Young University > http://teammccarthy.org/jay > > "The glory of God is Intelligence" - D&C 93 > _________________________________________________ > For list-related administrative tasks: > http://list.cs.brown.edu/mailman/listinfo/plt-dev _________________________________________________ For list-related administrative tasks: http://list.cs.brown.edu/mailman/listinfo/plt-dev
