[Gsll-devel] inverse of cl-array

[Liam Healy]

There isn't an inverse to cl-array at present.

Some thoughts about this, without having yet dived into the code:  my
first recommendation is to just make-marray for everything by default.
 When you need a regular CL array, use cl-array to extract it, and
then if you need to, copy it (see below).   The problem with supplying
an array directly to be made into a marray is that it may not be
"foreign friendly".  This won't make any difference on most
implementations, but on SBCL, you will get unpredictable results
because SBCL will avoid copying the array over to the C side and just
send a pointer to the GSL functions.  I could perhaps add the ability
to supply a foreign-friendly array, as made by make-ffa, as an
:initial-contents for make-marray.

If you are willing to always have the array copied, that could be done
pretty easily too.   As a side point, please note that changing an
element of an array extracted with cl-array will change the marray in
SBCL and have unpredictable results on other implementations.  This is
why I recommend you copy the array after you extract it.

Liam

On Tue, Feb 10, 2009 at 8:49 AM, Mirko Vukovic <mirko.vukovic at gmail.com> wrote:
>
>
> On Tue, Feb 10, 2009 at 5:09 AM, Niitsuma Hirotaka
> <hirotaka.niitsuma at gmail.com> wrote:
>>
>> I can not find convert function
>> #A(...) -> #m(...)
>>
>> ( cl-array is conversion #m -> #a )
>>
>> Thus I write the following ,but that looks slow.
>> --------------
>> (defun coerce-array-to-list (in-array)
>>   (map 'list
>>           #'identity
>>           (make-array (array-total-size in-array)
>>                             :element-type (array-element-type in-array)
>>                             :displaced-to in-array)))
>> ;borrow from
>> http://groups.google.com/group/comp.lang.lisp/browse_thread/thread/a925ca60d88d4047/cc06e579dfe840a7?lnk=gst&q=displaced+array
>>
>>
>> (defun appropriate-name (element-type ar)
>>  (make-marray element-type  :dimensions (array-dimensions ar)
>> :initial-contents  (coerce-array-to-list ar))
>> )
>> ---------------
>>
>> usage:
>> ( appropriate-name 'double-float #2A((1.0d0 2.0d0) (2.0d0 5.0d0)))
>> ->
>> #m((1.0d0 2.0d0) (2.0d0 5.0d0)))
>>
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>
> I don't know an answer better than yours.  I would name the function
> gsll-array.
> Also, since marray's are objects, you may want to look into its constructor
> to see how the array is stored.
>
> I was bitten a few times by the make-marray syntax that requires a list
> input.
>
> (As far as I see, lisp's coerce syntax prevents us from customizing it to do
> the job we want.)
>
> Mirko
>
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>
>