Re: Anyone understand this?

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…
> 
> 
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