anchor.diff:                       (setf (aref target dense-i) (aref source i)))))))
       (let ((new-sv (create-sv (height-of matrix :densep t)
                                (width-of matrix :densep t))))
  -      (compact (sv-left new-sv) (sv-left sv) #'map-row-densely)
  -      (compact (sv-right new-sv) (sv-right sv) #'map-column-densely)
  +      (compact (sv-left new-sv) (sv-left sv) #'dense-row-index)
  +      (compact (sv-right new-sv) (sv-right sv) #'dense-column-index)
         new-sv)))
   
   (defun save-svd (svd filename)
  
positive.code:                (map-matrix
                  (lambda (row column value i)
                    (declare (ignore value))
                    (let ((row (map-row-densely matrix row))
                          (column (map-column-densely matrix column)))
                      (setf (aref approximation i)
                            (funcall clip
                                     (+ (aref approximation i)
  
negative.code:   (let ((svd (subseq svd 0 max-n)))
      (lambda (row column)
        (let ((base-value (funcall base-approximator row column))
              (row (dense-row-index matrix row))
              (column (dense-column-index matrix column)))
          (svd-value svd row column :base-value base-value :clip clip)))))
  
  