[racket] performance problem in math/matrix

Modification of the above to use FlVector did not show a difference.


On Sun, Jan 20, 2013 at 2:35 PM, Jens Axel Søgaard <jensaxel at soegaard.net>wrote:

> 2013/1/20 Berthold Bäuml <berthold.baeuml at dlr.de>:
> >> Ah! The Numpy example uses floats and not doubles.
> >
> > On my machine Numpy says it is using float64, hence, double.
> >  big1.dtype.name -> float64
>
> Sorry for the confusion. I am used to the Racket documentation
> were float means single precision, so I misinterpreted the Numpy
> documentation.
>
> Also
>
> > numpy.random.random((5,5))
> array([[ 0.04748764,  0.15242073,  0.2366255 ,  0.86926654,  0.16586114],
>        [ 0.33117124,  0.7504899 ,  0.43179013,  0.1992083 ,  0.83266119],
>        [ 0.25741902,  0.36912007,  0.38273193,  0.29622522,  0.75817261],
>        [ 0.49313726,  0.20514653,  0.45329344,  0.964105  ,  0.77459153],
>        [ 0.5267172 ,  0.87269101,  0.34530438,  0.38218051,  0.05107181]])
>
> suggested, that the numbers were single precision. It turns out
> that random only produces 53 bit random floats.
>
> Anyways, here is a standard matrix multiplication algorithm in
> Typed Racket.
>
> #lang typed/racket
> (require racket/unsafe/ops
>          racket/flonum)
>
> (define-type NF Nonnegative-Fixnum)
>
> (: matrix* :
>    (Vectorof Flonum) (Vectorof Flonum) Index Index Index
>    -> (Vectorof Flonum))
> (define (matrix* A B m p n)
>   (define size (* m n))
>   (define: v : (Vectorof Flonum) (make-vector size 0.0))
>   (define index 0)
>   (: loop-i : NF -> (Vectorof Flonum))
>   (define (loop-i i)
>     (cond [(< i m)
>            (loop-j i 0)
>            (loop-i (+ i 1))]
>           [else v]))
>   (: loop-j : NF NF -> Void)
>   (define (loop-j i j)
>     (when (< j n)
>       (loop-k i j 0 0.0)
>       (set! index (+ index 1))
>       (loop-j i (+ j 1))))
>   (: loop-k : NF NF NF Flonum -> Void)
>   (define (loop-k i j k sum)
>     (define i*p (* i p))
>     (define k*n (* k n))
>     (cond
>       [(< k p)
>        (loop-k i j (+ k 1)
>                (+ sum
>                   (* (unsafe-vector-ref A (+ i*p k))
>                      (unsafe-vector-ref B (+ k*n j)))))]
>       [else
>        (vector-set! v index sum)]))
>   (loop-i 0))
>
> (define dim 200)
> (define A (build-vector (* dim dim) (λ (_) (random))))
> (define B (build-vector (* dim dim) (λ (_) (random))))
> (collect-garbage)
> (collect-garbage)
> (define A*B (time (matrix* A B dim dim dim)))
>
> /Jens Axel
>
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