anchor.diff:  (defun ensure-mask (lump)
     (when (dropout lump)
       (let ((x (nodes (x lump))))
  -      (unless (and (mask lump)
  -                   (= (mat-size x)
  -                      (mat-size (mask lump))))
  -        (setf (slot-value lump 'mask)
  -              (make-mat (mat-size x) :ctype flt-ctype)))))
  +      (setf (slot-value lump 'mask)
  +            (if (mask lump)
  +                (adjust! (mask lump) (mat-size x) 0)
  +                (make-mat (mat-size x) :ctype flt-ctype)))))
     (mask lump))
   
   (define-cuda-kernel (cuda-dropout-xorwow)
  
positive.code: 
  (defun ensure-randoms (lump)
    (let ((x (nodes (x lump))))
      (unless (and (randoms lump)
                   (= (mat-size x)
                      (mat-size (randoms lump))))
        (setf (slot-value lump 'randoms)
              (make-mat (mat-size x) :ctype flt-ctype))))
    (randoms lump))
  
  (defmethod transfer-lump ((lump ->sample-binary))
    (let ((x (x lump)))
  
negative.code:   "Add LUMP to BPN. MAX-N-STRIPES of LUMP gets set to equal that of
    the previous last, non-weight lump of BPN."
    (when (find-lump (name lump) bpn)
      (error "Cannot add ~S: ~
              a lump of same name has already been added to this network." lump))
    (setf (max-n-stripes lump) (max-n-stripes bpn))
    (vector-push-extend lump (slot-value bpn 'lumps) 1)
  