anchor.diff:      new-arr))
   
   (defun set-best-children! (n-trial node)
  -  ;;(declare (optimize (speed 3) (safety 0)))
     (let* ((dtree (node-dtree node))
            (gain-test (dtree-gain-test dtree))
            (max-children-gain most-negative-double-float)
  
positive.code:                  :max-depth max-depth :min-region-samples min-region-samples
                   :n-trial n-trial
                   :gain-test gain-test
                   :tmp-arr1 (make-array len :element-type 'fixnum :initial-element 0)
                   :tmp-index1 0
                   :tmp-arr2 (make-array len :element-type 'fixnum :initial-element 0)
  
negative.code: 
  (defun make-dtree (n-class datum-dim datamatrix target
                     &key (max-depth 5) (min-region-samples 1) (n-trial 10)
                       (gain-test #'entropy) (remove-sample-indices? t) sample-indices)
    (let* ((len (if sample-indices
                    (length sample-indices)
                    (array-dimension datamatrix 0)))
  