anchor.diff:  ")
   
   (defparameter +sphere-template+ "sphere {
  -  <~F,~F,~F>,0.5
  +  <~F,~F,~F>,0.25
     texture {
       pigment { color Yellow }
     }
  
positive.code:                  ;; Synchronize CUDA context.
                   (synchronize-context)
                   ;; Output POV file.
                   ;(sync-memory-block pos :device-to-host)
                   ;(output i pos)
                  )))))))
  
negative.code:           (initialize pos vel particles)
            (sync-memory-block pos :host-to-device)
            (sync-memory-block vel :host-to-device)
            ;(output 0 pos)
            ;; Do simulation.
            (time
             (loop repeat 300
  