[Matlisp-users] Re: [Matlisp-devel] Re: (DOT REAL-MAT COMPLEX-MAT) ERROR

[Raymond T. <to...@rt...>]

>>>>> "Raymond" == Raymond Toy <to...@rt...> writes:

>>>>> "Mike" == mak  <ma...@ll...> writes:
    Mike> Ray,
    Mike> I may have spoken too soon.  Yes, the SEGMENT violation is gone.  However, 
    Mike> I stumbled upon this.  I define three distinct vectors *WS*, *WD*, and D.
    Mike> Then I compute the following

    Mike> (dot *ws* d): 			      5.771771444577276d0
    Mike> (dot *wd* d): 			      #C(0.0d0 -8.946814341083627d0)
    Mike> (/ (m:dot *wd* d) (m:dot *ws* d)):    #C(1.0d0 0.0d0)

    Mike> ==> THIS SHOULD HAVE BEEN #C(0.0D0 -1.5500985142939754D0) <==

    Mike> Now what?  I'm clueless on how to track this one down.  

    Raymond> This is very, very weird.  I'll look in to it.  And actually, it's an

I have a sneaking suspicion that this is a compiler bug where it
thinks that the temp variable used to hold the result of zdotc/zdotu
is never modified.  And since that temp variable is initialized to the
constant #c(0d0 0d0), it leaves it in a fixed place.  Thus, the result
of zdotc is recycled over and over.  We don't see it if you save the
intermediate result because a copy is made.

In any case, I think the following solves the immediate problem:

(defmethod dot ((x complex-matrix) (y complex-matrix) &optional (conjugate-p t))
  (let* ((nxm (number-of-elements x))
	 (store-x (store x))
	 (store-y (store y))
	 (dot (if conjugate-p
		  (zdotc nxm store-x 1 store-y 1)
		  (zdotu nxm store-x 1 store-y 1))))
    (if (zerop (imagpart dot))
	(realpart dot)
	(complex (realpart dot) (imagpart dot)))))

I think this need to be fixed in ffi-cmu.lisp in some way.  There's no
telling what other bugs will be found because of this, if I'm right.

Ray