Adding ipython notebook to visualize stutter-invariance benchmarks.

* bench/stutter/stutter_bench.sh: Collect benchmarks for different
number of atomic propositions in a single csv file.
* bench/stutter/stutter.ipynb: Visualize benchmarks generated by
stutter_bench.sh.

bench/stutter/stutter_bench.sh

+#!/bin/sh
+
+OUTPUT=bench_formulas.csv
+RANDLTL=../../src/bin/randltl
+LTLFILT=../../src/bin/ltlfilt
+
+if test -f bench_formulas.csv; then
+  echo -n "$OUTPUT already exists. [a]ppend, [r]emove it or [q]uit?"
+  read ans
+  if test "$ans" = "r"; then
+    rm "$OUTPUT"
+  else if test "$ans" = "q" -o "$ans" != "a"; then
+    echo "abort."
+    exit 0
+  fi
+  fi
+fi
+
+for ap in 1 2 3 4; do
+  echo "Generating benchmarks for formulas with $ap atomic propositions..."
+  $RANDLTL $ap --tree-size=..30 -n 20000 | $LTLFILT --ap=$ap |
+  ./stutter_invariance_formulas -F- >> "$OUTPUT"
+done