forked from bartvdbraak/blender
7837f0e833
This commit: * Adds a 'compare_ff' function for absolute 'almost equal' comparison of floats. * Makes 'compare_vxvx' functions use that new 'compare_ff' one. * Adds a 'compare_ff_relative' function for secured ulp-based relative comparison of floats. * Adds matching 'compare_vxvx_relative' functions. * Adds some basic tests for compare_ff_relative. See https://randomascii.wordpress.com/2012/02/25/comparing-floating-point-numbers-2012-edition/ Note that we could replace our python/mathutils' EXPP_FloatsAreEqual() by BLI's compare_ff_relative (using a very small absolute max_diff), but these do not have exact same behavior... Left a comment there for now, we can do it later if/when we are sure it won't break anything!
88 lines
3.0 KiB
C++
88 lines
3.0 KiB
C++
/* Apache License, Version 2.0 */
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#include "testing/testing.h"
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#include "BLI_math.h"
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/* In tests below, when we are using -1.0f as max_diff value, we actually turn the function into a pure-ULP one. */
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/* Put this here, since we cannot use BLI_assert() in inline math files it seems... */
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TEST(math_base, CompareFFRelativeValid)
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{
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EXPECT_TRUE(sizeof(float) == sizeof(int));
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}
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TEST(math_base, CompareFFRelativeNormal)
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{
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float f1 = 1.99999988f; /* *(float *)&(*(int *)&f2 - 1) */
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float f2 = 2.00000000f;
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float f3 = 2.00000048f; /* *(float *)&(*(int *)&f2 + 2) */
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float f4 = 2.10000000f; /* *(float *)&(*(int *)&f2 + 419430) */
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const float max_diff = FLT_EPSILON * 0.1f;
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EXPECT_TRUE(compare_ff_relative(f1, f2, max_diff, 1));
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EXPECT_TRUE(compare_ff_relative(f2, f1, max_diff, 1));
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EXPECT_TRUE(compare_ff_relative(f3, f2, max_diff, 2));
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EXPECT_TRUE(compare_ff_relative(f2, f3, max_diff, 2));
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EXPECT_FALSE(compare_ff_relative(f3, f2, max_diff, 1));
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EXPECT_FALSE(compare_ff_relative(f2, f3, max_diff, 1));
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EXPECT_FALSE(compare_ff_relative(f3, f2, -1.0f, 1));
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EXPECT_FALSE(compare_ff_relative(f2, f3, -1.0f, 1));
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EXPECT_TRUE(compare_ff_relative(f3, f2, -1.0f, 2));
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EXPECT_TRUE(compare_ff_relative(f2, f3, -1.0f, 2));
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EXPECT_FALSE(compare_ff_relative(f4, f2, max_diff, 64));
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EXPECT_FALSE(compare_ff_relative(f2, f4, max_diff, 64));
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EXPECT_TRUE(compare_ff_relative(f1, f3, max_diff, 64));
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EXPECT_TRUE(compare_ff_relative(f3, f1, max_diff, 64));
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}
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TEST(math_base, CompareFFRelativeZero)
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{
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float f0 = 0.0f;
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float f1 = 4.2038954e-045f; /* *(float *)&(*(int *)&f0 + 3) */
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float fn0 = -0.0f;
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float fn1 = -2.8025969e-045f; /* *(float *)&(*(int *)&fn0 - 2) */
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const float max_diff = FLT_EPSILON * 0.1f;
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EXPECT_TRUE(compare_ff_relative(f0, f1, -1.0f, 3));
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EXPECT_TRUE(compare_ff_relative(f1, f0, -1.0f, 3));
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EXPECT_FALSE(compare_ff_relative(f0, f1, -1.0f, 1));
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EXPECT_FALSE(compare_ff_relative(f1, f0, -1.0f, 1));
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EXPECT_TRUE(compare_ff_relative(fn0, fn1, -1.0f, 8));
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EXPECT_TRUE(compare_ff_relative(fn1, fn0, -1.0f, 8));
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EXPECT_TRUE(compare_ff_relative(f0, f1, max_diff, 1));
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EXPECT_TRUE(compare_ff_relative(f1, f0, max_diff, 1));
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EXPECT_TRUE(compare_ff_relative(fn0, f0, max_diff, 1));
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EXPECT_TRUE(compare_ff_relative(f0, fn0, max_diff, 1));
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EXPECT_TRUE(compare_ff_relative(f0, fn1, max_diff, 1));
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EXPECT_TRUE(compare_ff_relative(fn1, f0, max_diff, 1));
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/* Note: in theory, this should return false, since 0.0f and -0.0f have 0x80000000 diff,
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* but overflow in substraction seems to break something here
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* (abs(*(int *)&fn0 - *(int *)&f0) == 0x80000000 == fn0), probably because int32 cannot hold this abs value.
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* this is yet another illustration of why one shall never use (near-)zero floats in pure-ULP comparison. */
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// EXPECT_FALSE(compare_ff_relative(fn0, f0, -1.0f, 1024));
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// EXPECT_FALSE(compare_ff_relative(f0, fn0, -1.0f, 1024));
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EXPECT_FALSE(compare_ff_relative(fn0, f1, -1.0f, 1024));
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EXPECT_FALSE(compare_ff_relative(f1, fn0, -1.0f, 1024));
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}
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