anchor.diff:                                    (or (not use-population-p)
                                         (< (n-steps state) (log 0.1 decay))))
                                (foo (ensure-batch-mean state subbatch-index)
  -                                  (ensure-batch-stddev
  +                                  (ensure-batch-variance
                                      state subbatch-index))
                                (foo (ensure-population-mean state)
  -                                  (ensure-population-stddev state))))))))))))
  +                                  (ensure-population-variance state))))))))))))
   
   (defclass-now ->batch-normalization (->weight)
     ((scale
  
positive.code:    ;; A list of means of (SIZE X), one for each subbatch, of which
     ;; there are (/ N-STRIPES BATCH-SIZE).
     (batch-mean :initform nil :accessor batch-mean)
     (batch-stddev :initform nil :accessor batch-stddev)
     (batch-size
      :initform nil :initarg :batch-size :reader batch-size
      :documentation "Normally all stripes participate in the batch.
  
negative.code:                        (reshape-and-displace! nx batch-dimensions start)
                         (reshape-and-displace! nl batch-dimensions start)
                         (foo (ensure-batch-mean state subbatch-index)
                              (ensure-batch-variance state
                                                     subbatch-index))))))))))
  
  (defmethod backward ((lump ->batch-normalized))
    (let* ((state (batch-normalization lump))
  