--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/common/floateq.py	Thu Jun 19 16:12:29 2008 -0400
@@ -0,0 +1,49 @@
+#
+# Determine if floating point numbers are very close
+###########
+
+import math
+
+DEFAULT_SANITY_CHECK_EPSILON = 1e-6
+
+def floateq(a, b, epsilon=DEFAULT_SANITY_CHECK_EPSILON):
+    """
+    Compare two floats, with some epsilon tolerance.
+    """
+    return absolute_relative_error(a, b) < epsilon
+
+def absolute_relative_error(a, b, epsilon=DEFAULT_SANITY_CHECK_EPSILON):
+    return abs(a - b) / (abs(a) + abs(b) + epsilon)
+
+def double_epsilon_multiplicative_eq(a, b, epsilon=DEFAULT_SANITY_CHECK_EPSILON):
+    """
+    Determine if doubles are equal to within a multiplicative factor of
+    L{epsilon}.
+    @note: This function should be preferred over
+    L{double_epsilon_additive_eq}, unless the values to be compared may
+    have differing signs.
+    @precondition: sign(a) == sign(b)
+    @rtype: bool
+    """
+    if a == b: return True
+    if a == 0 and b == 0: return True
+    assert a != 0
+    assert b != 0
+    assert sign(a) == sign(b)
+    if a > b: d = a / b
+    else: d = b / a
+    assert d >= 1
+    return True if d <= 1 + SANITY_CHECK_EPSILON else False
+
+def double_epsilon_additive_eq(a, b):
+    """
+    Determine if doubles are equal to within an additive factor of
+    L{SANITY_CHECK_EPSILON}.
+    @note: Prefer L{double_epsilon_multiplicative_eq} to this function
+    unless the values to be compared may have differing signs.
+    """
+    if a == b: return True
+    if a == 0 and b == 0: return True
+    assert sign(a) != sign(b)   # Should use SANITY_CHECK_EPSILON
+    d = math.fabs(a - b)
+    return d <= SANITY_CHECK_EPSILON