dump_demos.m: Check if file exists before demo and add timing. * dump_demos.m: Skip demo if output print file already exists. Add tic/toc timing for demo (calculation + plotting) and printing. This allows benchmarks and finding regressions which causes slow plotting or printing.

#!/bin/sh
#
# Like mv $1 $2, but if the files are the same, just delete $1.
# Status is 0 if $2 is changed, 1 otherwise.

if test -r $2; then
  if cmp $1 $2 > /dev/null; then
    echo $2 is unchanged
    rm -f $1
  else
    mv -f $1 $2
  fi
else
  mv -f $1 $2
fi