Re: Anyone understand this?

Here is properly working code, just FYI:

(and with the (fli:with-dynamic-lisp-array-pointer (parr arr2 :type :double), using a :START arg defaulting to zero makes the code portable into the future, when someday the function is fixed.)

#+:MACOSX
(defvar *vdsp-lib*
  "/System/Library/Frameworks/Accelerate.framework/Versions/A/Frameworks/vecLib.framework/Versions/A/libvDSP.dylib")

#+:MACOSX
(fli:define-foreign-function (_vdsp-dotprd "vDSP_dotprD" :source)
    ((va  :lisp-simple-1d-array)
     (ia  :long)
     (vb  :pointer)
     (ib  :long)
     (pc  (:pointer :double-float))
     (nel :long))
  :result-type :void
  :language :c
  :calling-convention :cdecl
  :module *vdsp-lib*)

#+:MACOSX
(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)
          (fli:incf-pointer parr start2)
          (_vdsp-dotprd arr1 1 parr 1 ans (length arr1))
          (fli:dereference ans))
        ))))



> On Jan 22, 2025, at 12:39, David McClain (as dbm at refined-audiometrics dot com) <[email protected]> wrote:
> 
> YES!! Thanks for that suggestion!
> 
> Use FLI:INCF-POINTER by START * 8 for a :DOUBLE array. And now it works!
> 
> Thanks for the suggestion!!
> 
> 
>> On Jan 22, 2025, at 12:36, David McClain <[email protected]> wrote:
>> 
>> I do seem to recall doing that sort of thing, many years ago when I wrote a direct memory file access mechanism for Lisp. Maybe…
>> 
>> 
>> 
>>> On Jan 22, 2025, at 12:35, Yuri Davidovsky <[email protected]> wrote:
>>> 
>>> 
>>> Is there a way to increment a pointer in a separate step after creation?
>>> 
>>>> On 22 Jan 2025, at 20:15, David McClain <[email protected]> wrote:
>>>> 
>>>> 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))))
>> 
>