gsakkis · March 12, 2012 09:11 · Mar 12, 2012
diff --git a/gistfile1.txt b/gistfile1.txt
@@ -0,0 +1,48 @@
+-2.695
+    reduced by ROUND_UP, ROUND_FLOOR, ROUND_HALF_UP, ROUND_HALF_EVEN
+    increased by ROUND_DOWN, ROUND_05UP, ROUND_CEILING, ROUND_HALF_DOWN
+-2.669, -2.699
+    reduced by ROUND_UP, ROUND_FLOOR, ROUND_HALF_UP, ROUND_HALF_DOWN, ROUND_HALF_EVEN
+    increased by ROUND_DOWN, ROUND_05UP, ROUND_CEILING
+-2.665
+    reduced by ROUND_UP, ROUND_FLOOR, ROUND_HALF_UP
+    increased by ROUND_DOWN, ROUND_05UP, ROUND_CEILING, ROUND_HALF_DOWN, ROUND_HALF_EVEN
+-2.661, -2.691
+    reduced by ROUND_UP, ROUND_FLOOR
+    increased by ROUND_DOWN, ROUND_05UP, ROUND_CEILING, ROUND_HALF_UP, ROUND_HALF_DOWN, ROUND_HALF_EVEN
+-2.655
+    reduced by ROUND_UP, ROUND_05UP, ROUND_FLOOR, ROUND_HALF_UP, ROUND_HALF_EVEN
+    increased by ROUND_DOWN, ROUND_CEILING, ROUND_HALF_DOWN
+-2.609, -2.659
+    reduced by ROUND_UP, ROUND_05UP, ROUND_FLOOR, ROUND_HALF_UP, ROUND_HALF_DOWN, ROUND_HALF_EVEN
+    increased by ROUND_DOWN, ROUND_CEILING
+-2.605
+    reduced by ROUND_UP, ROUND_05UP, ROUND_FLOOR, ROUND_HALF_UP
+    increased by ROUND_DOWN, ROUND_CEILING, ROUND_HALF_DOWN, ROUND_HALF_EVEN
+-2.601, -2.651
+    reduced by ROUND_UP, ROUND_05UP, ROUND_FLOOR
+    increased by ROUND_DOWN, ROUND_CEILING, ROUND_HALF_UP, ROUND_HALF_DOWN, ROUND_HALF_EVEN
+2.601, 2.651
+    reduced by ROUND_DOWN, ROUND_FLOOR, ROUND_HALF_UP, ROUND_HALF_DOWN, ROUND_HALF_EVEN
+    increased by ROUND_UP, ROUND_05UP, ROUND_CEILING
+2.605
+    reduced by ROUND_DOWN, ROUND_FLOOR, ROUND_HALF_DOWN, ROUND_HALF_EVEN
+    increased by ROUND_UP, ROUND_05UP, ROUND_CEILING, ROUND_HALF_UP
+2.609, 2.659
+    reduced by ROUND_DOWN, ROUND_FLOOR
+    increased by ROUND_UP, ROUND_05UP, ROUND_CEILING, ROUND_HALF_UP, ROUND_HALF_DOWN, ROUND_HALF_EVEN
+2.655
+    reduced by ROUND_DOWN, ROUND_FLOOR, ROUND_HALF_DOWN
+    increased by ROUND_UP, ROUND_05UP, ROUND_CEILING, ROUND_HALF_UP, ROUND_HALF_EVEN
+2.661, 2.691
+    reduced by ROUND_DOWN, ROUND_05UP, ROUND_FLOOR, ROUND_HALF_UP, ROUND_HALF_DOWN, ROUND_HALF_EVEN
+    increased by ROUND_UP, ROUND_CEILING
+2.665
+    reduced by ROUND_DOWN, ROUND_05UP, ROUND_FLOOR, ROUND_HALF_DOWN, ROUND_HALF_EVEN
+    increased by ROUND_UP, ROUND_CEILING, ROUND_HALF_UP
+2.669, 2.699
+    reduced by ROUND_DOWN, ROUND_05UP, ROUND_FLOOR
+    increased by ROUND_UP, ROUND_CEILING, ROUND_HALF_UP, ROUND_HALF_DOWN, ROUND_HALF_EVEN
+2.695
+    reduced by ROUND_DOWN, ROUND_05UP, ROUND_FLOOR, ROUND_HALF_DOWN
+    increased by ROUND_UP, ROUND_CEILING, ROUND_HALF_UP, ROUND_HALF_EVEN
diff --git a/test_quantize.py b/test_quantize.py
@@ -0,0 +1,49 @@
+
+import decimal as d
+from collections import defaultdict
+from operator import itemgetter
+
+exp = d.Decimal("0.01")
+
+numbers = map(d.Decimal, [
+    "-2.601", "-2.605", "-2.609",
+    "-2.651", "-2.655", "-2.659",
+    "-2.661", "-2.665", "-2.669",
+    "-2.691", "-2.695", "-2.699",
+
+    "2.601", "2.605", "2.609",
+    "2.651", "2.655", "2.659",
+    "2.661", "2.665", "2.669",
+    "2.691", "2.695", "2.699",
+])
+
+roundings = [
+    d.ROUND_UP,
+    d.ROUND_DOWN,
+    d.ROUND_05UP,
+    d.ROUND_FLOOR,      
+    d.ROUND_CEILING,
+    d.ROUND_HALF_UP,
+    d.ROUND_HALF_DOWN,
+    d.ROUND_HALF_EVEN,  
+]
+
+groups = defaultdict(list)
+
+for n in numbers:
+    reduced, increased = [], []
+    for r in roundings:
+        q = n.quantize(exp, r)
+        if q > n:
+            increased.append(r)
+        elif q < n:
+            reduced.append(r)
+    if reduced or increased:
+        groups[tuple(reduced), tuple(increased)].append(n)
+
+assert len(groups) <= 16, len(groups)
+
+for (reduced, increased), group in sorted(groups.iteritems(), key=itemgetter(1)):
+    print ", ".join(map(str, group))
+    print "    reduced by", ", ".join(reduced)
+    print "    increased by", ", ".join(increased)