anchor.diff:      ;; add ample margin for *next* GC: 200 MiB
       (incf (sb-alien:extern-alien "auto_gc_trigger" sb-alien:long) (* 200 1024 1024))
       #|(sb-ext:gc :full t)|#)
  -  #+ccl
  +  #+clozure
     (progn
       (ccl::configure-egc 32768 65536 98304)
       (ccl::set-lisp-heap-gc-threshold (* 384 1024 1024))
  
positive.code: (defun seed-random-state (seed) ; seed is a integer
    (declare (ignorable seed))
    #+sbcl (sb-ext:seed-random-state seed)
    #+ccl (flet ((get-bits (&aux bits)
                   (multiple-value-setq (seed bits) (floor seed ccl::mrg31k3p-limit))
                   bits))
            (multiple-value-bind (x0 x1 x2 x3 x4 x5)
                (apply 'values (loop :repeat 6 :collect (get-bits)))
              (when (zerop (logior x0 x1 x2))
                (setf x0 (logior (get-bits) 1)))
              (when (zerop (logior x3 x4 x5))
                (setf x3 (logior (get-bits) 1)))
              (ccl::initialize-mrg31k3p-state x0 x1 x2 x3 x4 x5)))
    #-(or sbcl ccl) (make-random-state *initial-random-state*))
  
  (defun call-with-determinism (seed thunk)
    ;;; The seed is an arbitrary object from (a hash of) which we initialize
  
negative.code: (defun get-optimization-settings ()
    "Get current compiler optimization settings, ready to PROCLAIM again"
    (let ((settings '(speed space safety debug compilation-speed)))
      #-(or clisp clozure sbcl)
      (warn "xcvb-driver::get-optimization-settings does not your implementation. Please help me fix that.")
      #.`(loop :for x :in settings
           ,@(or #+clozure '(:for v :in '(ccl::*nx-speed* ccl::*nx-space* ccl::*nx-safety* ccl::*nx-debug* ccl::*nx-cspeed*)))
           :for y = (or #+clisp (gethash x system::*optimize*)
  