[GSLL-devel] Fixing up make-grid-data for clisp (was making copy-to working in clisp+grid: fix to element-type)

[Liam Healy]

My fix (as opposed to your fix) to the problem you reported in your
previous email should not exhibit this problem, see my previous email. A
better summary is CLISP is not a preferred platform for anything. There is
a Windows port of SBCL, and has been for quite some time. A better
cross-check on portability would be CCL.

Liam


On Fri, Jan 4, 2013 at 11:47 AM, Mirko Vukovic <mirko.vukovic at gmail.com>wrote:

> This is a follow up on my posted fix to copy-to.  For some reason this has
> triggered another
> error.  I do not understand how that other error is triggered.  The error
> and the fix are discussed
> at the bottom of the email
>
> On Fri, Jan 4, 2013 at 10:39 AM, Mirko Vukovic <mirko.vukovic at gmail.com>wrote:
>
>> The following works in sbcl+grid:
>>
>> (copy-to (make-array 2 :element-type 'double-float :initial-contents
>> '(1.0d0 2.0d0)) 'grid:foreign-array)
>>
>> But it does not work in clisp+grid.
>>
>> The root cause lies in the function grid/array.lisp/element-type.  It
>> uses `(array-element-type grid)'.
>>
>> But this can present a problem.  Quoting hyperspec:
>>
>> (Because of *array* <http://26_glo_a.htm#array> *upgrading*, this *type
>> specifier* <http://26_glo_t.htm#type_specifier> can in some cases denote
>> a *supertype* <http://26_glo_s.htm#supertype> of the *expressed array
>> element type* <http://26_glo_e.htm#expressed_array_element_type> of the
>> *array*.)
>>
>> In CLISP, array-element-type returns `T' when passed #(1d0 2d0)
>>
>> It returns T even when passed a simple array:
>>
>> (array-element-type (make-array 2 :element-type 'double-float
>> :initial-contents
>>                       '(1.0d0 2.0d0)
>>                       :adjustable nil
>>                       :fill-pointer nil
>>                       :displaced-to nil) )
>>
>> The proposed fix is
>>
>> (defmethod element-type ((grid array))
>>   (type-of (row-major-aref grid 0))
>>   #+skip(array-element-type grid))
>>
>> Now copy-to works in clisp as well.
>>
>> Mirko
>>
>>
>> After finishing this, I recompiled afresh, and got another error that I
> traced to make-grid-data and make-array
>
> In clisp, make-array will return an array of NIL's even if the
> element-type is specified as double float.  In SBCL make-array
> will return an array filled with 1d0.
>
> I had to add some clisp specific code to make-grid-data in order for it to
> initialize properly.
>
> First, a helper function:
> (defun default-element (element-type)
>    "Return a default element depending on element-type
> "
>    (let ((a-list '((double-float . 1d0)
>            (symbol . T))))
>      (let ((match (cdr (assoc element-type a-list))))
>        (assert match ()
>            "Default element type undefined for element-type ~a"
>            element-type)
>        match)))
>
> And second, a bit of set-up code in make-grid-data.  I broke apart the
> (let* statement
> to provide an explicit initial element if it has not been specified
> already:
>
> (defmethod make-grid-data
>   ((type (eql 'array)) dimensions rest-spec
>    &key (initial-element nil initial-element-p)
>    (initial-contents nil initial-contents-p))
>   (let ((element-type (top-spec-type rest-spec)))
>     #+clisp
>     (unless (or initial-element-p
>         initial-contents-p)
>       (setf initial-element (default-element element-type)
>         initial-element-p t))
>     (let ((array ... UNCHANGED
>
>
> Summary:  To fix to copy-to, I modified (defmethod element-type ((grid
> array))
> For some unknown reason, that triggered an error in the array
> initialization routine.
> To fix that, I had to add code to make-grid-data, so that it fills
> double-float arrays with 0d0
> instead of NIL's
>
> I will continue using this code to see if there are additional problems.
>
> BTW, I realize that CLISP is not a preferred platform for speedy
> computation, but that is what I use
> on Windows, until SBCL gets officially ported to it.  And in addition, it
> is a nice cross-check on portability.
>
> Mirko
>
>
>
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>
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