anchor.diff:      ;; FIXEXT:
       (assert (not (same-stripes-p x)))
       (if (transpose-weights-p lump)
  +        ;; a = x*w'
           (gemm! (flt 1) (nodes x) (nodes weights)
                          (flt 0) (nodes lump)
                          :transpose-b? t :lda nx :ldb nx :ldc nl
                          :m n-stripes :n nl :k nx)
  +        ;; a = x*w
           (gemm! (flt 1) (nodes x) (nodes weights)
                          (flt 0) (nodes lump)
                          :lda nx :ldb nl :ldc nl
  
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: (defun ensure-multipliers (lump)
    (when (variance lump)
      (let ((x (nodes (x lump))))
        (setf (slot-value lump 'multipliers)
              (if (multipliers lump)
                  (adjust! (multipliers lump) (mat-size x) 0)
                  (make-mat (mat-size x) :ctype flt-ctype)))))
    (multipliers lump))
  
  (defun mgn! (l x multipliers variance)
  