Re: Anyone understand this?

Indeed, going back to the examples in the LW Manual,

This produces 10.0 instead of 30.0.

(let* ((arr (make-array 3
                        :element-type 'double-float
                        :allocation :pinnable
                        :initial-contents '(10d0 20d0 30d0))))
  (hcl:with-pinned-objects (arr)
    (fli:with-dynamic-lisp-array-pointer (parr arr :start 2 :type :double-float)
      (fli:dereference parr))))


> On Jan 22, 2025, at 12:11, David McClain (as dbm at refined-audiometrics dot com) <[email protected]> wrote:
> 
> More properly, it appears to be a bug in FLI::SET-DYNAMIC-LISP-ARRAY-POINTER, which is part of the macro expansion.
> 
> 
> 
> 
>> On Jan 22, 2025, at 12:10, David McClain <[email protected]> wrote:
>> 
>> It appears now that the fault actually lies with FLI:WITH-DYNAMIC-LISP-ARRAY-POINTER. 
>> 
>> Using this code to produce a dummy second pointer with explicit :START 0, alongside the actual pointer of interest with a non-zero :START parameter, and then stepping through this code with a breakpoint set where the pointers are created, shows that both pointers produce identical FLI:POINTER objects. There is no base + offset in a composite object. The POINTER is expected to have a reduced direct address. And the two pointers do not differ when they ought to be different.
>> 
>> So looks like a bug in FLI:WITH-DYNAMIC-LISP-ARRAY-POINTER.
>> 
>> (defun vdot (arr1 arr2 &key (start2 0))
>>   ;; intended for pre-decimation FIR filtering, where:
>>   ;;   arr1 = FIR filter kernel
>>   ;;   arr2 = input data buffer
>>   ;;   nel  = length of FIR filter (ntaps)
>>   ;;   start2 = starting position in data buffer for filtering,
>>   ;;            as kernel steps along by ndec
>>   (declare (array (double-float *) arr1 arr2))
>>   (fli:with-dynamic-foreign-objects ()
>>     (let ((ans (fli:allocate-dynamic-foreign-object :type :double-float)))
>>       (hcl:with-pinned-objects (arr2)
>>         (fli:with-dynamic-lisp-array-pointer (parr arr2 :type :double-float :start start2)
>>           (fli:with-dynamic-lisp-array-pointer (parrx arr2 :type :double-float :start 0)
>>             (_vdsp-dotprd arr1 1 parr 1 ans (length arr1))
>>             (inspect (list parr parrx))
>>             (fli:dereference ans)))
>>         ))))
>> 
>> #|
>> (let* ((arr2 (make-array 5
>>                          :element-type 'double-float
>>                          :allocation :pinnable
>>                          :initial-contents '(1d0 2d0 3d0 4d0 5d0)))
>>        (arr1 (make-array 3
>>                          :element-type 'double-float
>>                          :allocation :pinnable
>>                          :initial-contents '(10d0 20d0 30d0))))
>>   (vdot arr1 arr2 :start2 1)) ;; should produce 200.0, but produces 140.0.
>> |#
>> 
>> 
>>> On Jan 22, 2025, at 11:57, Yuri Davidovsky (as work at disclosure dot ie) <[email protected]> wrote:
>>> 
>>> That’s some classy email formatting. 
>>> 
>>>> On 22 Jan 2025, at 18:52, David McClain (as dbm at refined-audiometrics dot com) <[email protected]> wrote…
>>> 
>>> 
>>> _______________________________________________
>>> Lisp Hug - the mailing list for LispWorks users
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>> 
>