[Gsll-devel] small modification to blas2.lisp

[Mirko Vukovic]

On Wed, May 14, 2008 at 5:02 PM, Liam Healy <lhealy at common-lisp.net> wrote:
> On Wed, May 14, 2008 at 2:23 PM, Mirko Vukovic <mirko.vukovic at gmail.com> wrote:
>> Hi,
>>
>>  I was playing with gsll and blas.  I modified the cblas-transpose
>>  definition in blas2.lisp (see top of file) to capture a few more
>>  values:
>>
>>  Here is the new version:
>>
>>  (cffi:defcenum cblas-transpose
>>   "CBLAS_TRANSPOSE from /usr/include/gsl/gsl_cblas.h."
>>   (:notrans 111) (:trans 112) (:conjtrans 113))
>
> I fail to see the difference with what is in there now:
> (cffi:defcenum cblas-transpose
>  "CBLAS_TRANSPOSE from /usr/include/gsl/gsl_cblas.h."
>  (:notrans 111) :trans :conjtrans)
> See http://common-lisp.net/project/cffi/manual/html_node/defcenum.html#defcenum
> "If value is omitted its value will either be 0, if it's the first
> entry, or it it will continue the progression from the last specified
> value."
> so :trans gets 112, :conjtrans 113 by default.

I was wondering why the other values were omitted.
>
>>
>>  I am posting it here because I was not able to download with svn so I
>>  don't have versioning for gsll.
>>
>>  Also, here is a code snippet that I used to test for tridiagonal
>>  matrix solving that also uses gsll-s blas2 routine gemv to double
>>  check that things work.
>>
>>  (in-package :gsll)
>>  ;; solve a tridiagonal system and then verify result by matrix multiplication
>>  ;; uses solve-tridiagonal and gemv
>>  (let* ((dim 6)
>>        (dim- (- dim 1)))
>>   (let ((d (make-array dim :element-type 'double-float :initial-element -2.d0))
>>         (e (make-array dim- :element-type 'double-float :initial-element 0.2d0))
>>         (f (make-array dim- :element-type 'double-float :initial-element 1.d0))
>>         (x (make-array dim :element-type 'double-float :initial-element 0.d0))
>>         (b (make-array dim :element-type 'double-float :initial-element 0.5d0))
>>         (mat (make-array (list dim dim)
>>                          :element-type 'double-float
>>                          :initial-element 0.d0)))
>>
>>     ;; load matrix
>>     (loop for i from 0 below dim-
>>        do (progn
>>             (setf (aref mat i i) (aref d i))
>>             (setf (aref mat (+ i 1) i) (aref f i))
>>             (setf (aref mat i (+ i 1)) (aref e i))))
>>     (setf (aref mat dim- dim-) (aref d dim-))
>>
>>     ;; gsl operations
>>     (letm ((d* (vector-double-float d))
>>            (e* (vector-double-float e))
>>            (f* (vector-double-float f))
>>            (x* (vector-double-float x))
>>            (b* (vector-double-float b))
>>            (v2* (vector-double-float
>>                        (make-array dim :element-type 'double-float
>>                                        :initial-element 0.d0)))
>>            (mat* (matrix-double-float mat)))
>>       (solve-tridiagonal d* e* f* b* x*)
>>       ;; gemv returns the result in the last argument
>>       (gemv :notrans 1.d0 mat* x* 0.d0 v2*)
>>       (data v2*))))
>>
>>  I am sure this code betrays my lack of lisp experience.  So feel free
>>  to clean it up if you want it included in the verification part.
>>
>>  Mirko
>
> I might make a few simplifications; #'1- to do decrementing and
> I don't think there's a need to make arrays in CL and then remake
> them on the foreign side.   It is possibly a candidate for
> example/ regression tests.
>
> Liam
>
I agree for regression that there is no need to duplicate the arrays.  But,

1) I will be using the arrays outside of (letm ...) to plot them etc
2) I am still feeling my way around.  Even the above point may be
un-necessary, with, for example the (data ... function)

Mirko