Hi Robby, Please pardon my ignorance, but is there an easy to use thread library with Racket? I've used threads in other environments and I don't recall so many restrictions.
For example, how would you do something like a %-done meter if you have very limited ability to instrument the code you are metering? Thanks, -Joe On Thu, Jul 25, 2013 at 5:40 PM, Robby Findler <ro...@eecs.northwestern.edu>wrote: > hashes are definitely not future-safe, unfortunately. > > Robby > > > On Thu, Jul 25, 2013 at 6:50 PM, Joe Gilray <jgil...@gmail.com> wrote: > >> Here is an update: >> >> I rewrote gcd and used a hash-table for the squares check. The >> hash-table change sped up the sequential code about 10x! Then I tried >> using future / touch and it seems to improve the performance a little, but >> there is quite a bit of blocking (on >= and hash-ref) still. >> >> New code below. >> >> -Joe >> >> ; function that searches for progressive numbers for a given range of b >> values >> (define (find-progressive-num2 b-start b-end b-incr lim ht) >> (define (mgcd a b) (if (= b 0) a (mgcd b (modulo a b)))) >> (for/sum ([b (in-range b-start b-end b-incr)]) >> (let loopa ([a (add1 b)] [suma 0]) >> (cond >> [(> (mgcd a b) 1) (loopa (add1 a) suma)] >> [(>= (* a a a b) lim) suma] >> [else >> (let loopc ([c 1] [sumc 0]) >> (define n (+ (* a a a c c b) (* c b b))) >> (cond >> [(>= n lim) (loopa (add1 a) (+ suma sumc))] >> [(hash-has-key? ht n) (loopc (add1 c) (+ sumc n))] >> [else (loopc (add1 c) sumc)]))])))) >> >> ;(require future-visualizer) >> (define (euler141b) >> (define lim 1000000000000) >> (define ht (make-hash)) >> (for ([i (in-range 1 1000000)]) (hash-set! ht (sqr i) 1)) >> ; (visualize-futures >> (let ([f1 (future (λ () (find-progressive-num2 1 1000 4 lim ht)))] >> [f2 (future (λ () (find-progressive-num2 2 1000 4 lim ht)))] >> [f3 (future (λ () (find-progressive-num2 3 1000 4 lim ht)))]) >> (+ (find-progressive-num2 4 1000 4 lim ht) (touch f1) (touch f2) >> (touch f3)))) >> >> >> On Wed, Jul 24, 2013 at 9:46 PM, Robby Findler < >> ro...@eecs.northwestern.edu> wrote: >> >>> You might try places. Writing your own gcd seems straightforward. I'm >>> not sure about integer-sqrt?, tho. Maybe you could make a table or >>> something if you know there are not that many numbers. >>> >>> Or maybe someone will adjust the runtime to make those future safe! >>> >>> Robby >>> >>> >>> On Wed, Jul 24, 2013 at 11:34 PM, Joe Gilray <jgil...@gmail.com> wrote: >>> >>>> So I should write my own (gcd ) and (square? ) functions? >>>> >>>> I can try that, but isn't there a simple way to use threads? >>>> >>>> Thanks, >>>> -Joe >>>> >>>> >>>> >>>> >>>> On Wed, Jul 24, 2013 at 7:47 PM, Robby Findler < >>>> ro...@eecs.northwestern.edu> wrote: >>>> >>>>> When I run this, the future visualizer shows that gcd and >>>>> square-number? block the futures. square-number? is implemented in TR and >>>>> if you take it, you find that integer-sqrt also blocks the futures. I'm >>>>> not >>>>> sure if those functions can be made to run safely in futures or not. >>>>> >>>>> Robby >>>>> >>>>> >>>>> On Wed, Jul 24, 2013 at 7:26 PM, Joe Gilray <jgil...@gmail.com> wrote: >>>>> >>>>>> I have a ProjectEuler problem that I wanted to speed up so I thought >>>>>> I would try to speed it up with future / touch. >>>>>> >>>>>> I tried the following: >>>>>> >>>>>> ; function that searches for progressive numbers for a given range of >>>>>> b values >>>>>> (define (find-progressive-num b-start b-end b-incr lim) >>>>>> (for/sum ([b (in-range b-start b-end b-incr)]) >>>>>> (let loopa ([a (add1 b)] [suma 0]) >>>>>> (cond >>>>>> [(> (gcd a b) 1) (loopa (add1 a) suma)] >>>>>> [(>= (* a a a b) lim) suma] >>>>>> [else >>>>>> (let loopc ([c 1] [sumc 0]) >>>>>> (define n (+ (* a a a c c b) (* c b b))) >>>>>> (cond >>>>>> [(>= n lim) (loopa (add1 a) (+ suma sumc))] >>>>>> [(square-number? n) (loopc (add1 c) (+ sumc n))] >>>>>> [else (loopc (add1 c) sumc)]))])))) >>>>>> >>>>>> ; ProjectEuler problem #141 >>>>>> ; n = q * d + r >>>>>> ; q/d = d/r = a/b (where a and b are relatively prime) >>>>>> ; so d = a*r/b and q = a^2 * r / b^2 >>>>>> ; since a and b are coprime r must be divisible by b^2 or r = c*b^2 >>>>>> ; substituting: d = a*c*b and q = a^2*c >>>>>> ; n = a^3 * c^2 * b + c * b^2 >>>>>> (define (euler141) >>>>>> (define lim 10000000000) >>>>>> (let ([f1 (future (λ () (find-progressive-num 1 1000 2 lim)))]) >>>>>> (+ (find-progressive-num 2 1000 2 lim) (touch f1)))) >>>>>> >>>>>> Unfortunately this runs no faster than the sequential version. I >>>>>> tried using the future-visualizer but I couldn't understand what it was >>>>>> telling me (I guess some operation is blocking). I also tried finer >>>>>> grained threads (one for each value of b), but that did no better. >>>>>> >>>>>> Can anyone give me some pointers to successfully using future / touch? >>>>>> >>>>>> Thanks, >>>>>> -Joe >>>>>> >>>>>> ____________________ >>>>>> Racket Users list: >>>>>> http://lists.racket-lang.org/users >>>>>> >>>>>> >>>>> >>>> >>> >> >
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