blender/tests/gtests/blenlib/BLI_math_base_test.cc

/* Apache License, Version 2.0 */

#include "testing/testing.h"

#include "BLI_math.h"

/* In tests below, when we are using -1.0f as max_diff value, we actually turn the function into a
 * pure-ULP one. */

/* Put this here, since we cannot use BLI_assert() in inline math files it seems... */
TEST(math_base, CompareFFRelativeValid)
{
  EXPECT_TRUE(sizeof(float) == sizeof(int));
}

TEST(math_base, CompareFFRelativeNormal)
{
  float f1 = 1.99999988f; /* *(float *)&(*(int *)&f2 - 1) */
  float f2 = 2.00000000f;
  float f3 = 2.00000048f; /* *(float *)&(*(int *)&f2 + 2) */
  float f4 = 2.10000000f; /* *(float *)&(*(int *)&f2 + 419430) */

  const float max_diff = FLT_EPSILON * 0.1f;

  EXPECT_TRUE(compare_ff_relative(f1, f2, max_diff, 1));
  EXPECT_TRUE(compare_ff_relative(f2, f1, max_diff, 1));

  EXPECT_TRUE(compare_ff_relative(f3, f2, max_diff, 2));
  EXPECT_TRUE(compare_ff_relative(f2, f3, max_diff, 2));

  EXPECT_FALSE(compare_ff_relative(f3, f2, max_diff, 1));
  EXPECT_FALSE(compare_ff_relative(f2, f3, max_diff, 1));

  EXPECT_FALSE(compare_ff_relative(f3, f2, -1.0f, 1));
  EXPECT_FALSE(compare_ff_relative(f2, f3, -1.0f, 1));

  EXPECT_TRUE(compare_ff_relative(f3, f2, -1.0f, 2));
  EXPECT_TRUE(compare_ff_relative(f2, f3, -1.0f, 2));

  EXPECT_FALSE(compare_ff_relative(f4, f2, max_diff, 64));
  EXPECT_FALSE(compare_ff_relative(f2, f4, max_diff, 64));

  EXPECT_TRUE(compare_ff_relative(f1, f3, max_diff, 64));
  EXPECT_TRUE(compare_ff_relative(f3, f1, max_diff, 64));
}

TEST(math_base, CompareFFRelativeZero)
{
  float f0 = 0.0f;
  float f1 = 4.2038954e-045f; /* *(float *)&(*(int *)&f0 + 3) */

  float fn0 = -0.0f;
  float fn1 = -2.8025969e-045f; /* *(float *)&(*(int *)&fn0 - 2) */

  const float max_diff = FLT_EPSILON * 0.1f;

  EXPECT_TRUE(compare_ff_relative(f0, f1, -1.0f, 3));
  EXPECT_TRUE(compare_ff_relative(f1, f0, -1.0f, 3));

  EXPECT_FALSE(compare_ff_relative(f0, f1, -1.0f, 1));
  EXPECT_FALSE(compare_ff_relative(f1, f0, -1.0f, 1));

  EXPECT_TRUE(compare_ff_relative(fn0, fn1, -1.0f, 8));
  EXPECT_TRUE(compare_ff_relative(fn1, fn0, -1.0f, 8));

  EXPECT_TRUE(compare_ff_relative(f0, f1, max_diff, 1));
  EXPECT_TRUE(compare_ff_relative(f1, f0, max_diff, 1));

  EXPECT_TRUE(compare_ff_relative(fn0, f0, max_diff, 1));
  EXPECT_TRUE(compare_ff_relative(f0, fn0, max_diff, 1));

  EXPECT_TRUE(compare_ff_relative(f0, fn1, max_diff, 1));
  EXPECT_TRUE(compare_ff_relative(fn1, f0, max_diff, 1));

  /* Note: in theory, this should return false, since 0.0f  and -0.0f have 0x80000000 diff,
   *       but overflow in subtraction seems to break something here
   *       (abs(*(int *)&fn0 - *(int *)&f0) == 0x80000000 == fn0), probably because int32 cannot
   * hold this abs value. this is yet another illustration of why one shall never use (near-)zero
   * floats in pure-ULP comparison. */
  //  EXPECT_FALSE(compare_ff_relative(fn0, f0, -1.0f, 1024));
  //  EXPECT_FALSE(compare_ff_relative(f0, fn0, -1.0f, 1024));

  EXPECT_FALSE(compare_ff_relative(fn0, f1, -1.0f, 1024));
  EXPECT_FALSE(compare_ff_relative(f1, fn0, -1.0f, 1024));
}