Add ULP error plot script

Simple script to visualize the output of the ulp test tool, e.g.

$ build/bin/ulp -e .0001 log 0.5 2.0 2345678 | math/tools/plot.py

1 files changed, 56 insertions, 0 deletions

diff --git a/math/tools/plot.py b/math/tools/plot.py
new file mode 100755
index 0000000..09c8ec6
--- /dev/null
+++ b/math/tools/plot.py
@@ -0,0 +1,56 @@
+#!/usr/bin/python
+
+# ULP error plot tool.
+#
+# Copyright (c) 2019, Arm Limited.
+# SPDX-License-Identifier: MIT
+
+import numpy as np
+import matplotlib.pyplot as plt
+import sys
+import re
+
+# example usage:
+# build/bin/ulp -e .0001 log 0.5 2.0 2345678 | math/tools/plot.py
+
+def fhex(s):
+	return float.fromhex(s)
+
+def parse(f):
+	xs = []
+	ys = []
+	es = []
+	# Has to match the format used in ulp.c
+	r = re.compile(r'[^ (]+\(([^ )]*)\) got [^ ]+ want ([^ ]+) [^ ]+ ulp err ([^ ]+)')
+	for line in f:
+		m = r.match(line)
+		if m:
+			x = fhex(m.group(1))
+			y = fhex(m.group(2))
+			e = float(m.group(3))
+			xs.append(x)
+			ys.append(y)
+			es.append(e)
+		elif line.startswith('PASS') or line.startswith('FAIL'):
+			# Print the summary line
+			print(line)
+	return xs, ys, es
+
+def plot(xs, ys, es):
+	if len(xs) < 2:
+		print('not enough samples')
+		return
+	a = min(xs)
+	b = max(xs)
+	fig, (ax0,ax1) = plt.subplots(nrows=2)
+	es = map(abs, es) # ignore the sign
+	emax = max(es)
+	ax0.text(a+(b-a)*0.7, emax*0.8, '%s\n%g'%(emax.hex(),emax))
+	ax0.plot(xs,es,'rx')
+	ax0.grid()
+	ax1.plot(xs,ys,'rx')
+	ax1.grid()
+	plt.show()
+
+xs, ys, es = parse(sys.stdin)
+plot(xs, ys, es)