X-Git-Url: https://git.sesse.net/?p=movit;a=blobdiff_plain;f=fp16_test.cpp;h=7a9d56612b53dbe942d2b6d1b8a079b5cdfa6c3c;hp=d5d7fc04c22396a48fc7bbf73b239629f6fd39e6;hb=7f1fabb816ee5010be83abf5da58e92429609547;hpb=1f4a7aefd4a149e93a1dc41f85958e827670c98b

diff --git a/fp16_test.cpp b/fp16_test.cpp
index d5d7fc0..7a9d566 100644
--- a/fp16_test.cpp
+++ b/fp16_test.cpp
@@ -4,77 +4,92 @@
 #include <gtest/gtest.h>
 
 namespace movit {
+namespace {
+
+fp16_int_t make_fp16(unsigned short x)
+{
+	fp16_int_t ret;
+	ret.val = x;
+	return ret;
+}
+
+}  // namespace
 
 TEST(FP16Test, Simple) {
-	EXPECT_EQ(0x0000, fp64_to_fp16(0.0));
-	EXPECT_DOUBLE_EQ(0.0, fp16_to_fp64(0x0000));
+	EXPECT_EQ(0x0000, fp32_to_fp16(0.0).val);
+	EXPECT_DOUBLE_EQ(0.0, fp16_to_fp32(make_fp16(0x0000)));
 
-	EXPECT_EQ(0x3c00, fp64_to_fp16(1.0));
-	EXPECT_DOUBLE_EQ(1.0, fp16_to_fp64(0x3c00));
+	EXPECT_EQ(0x3c00, fp32_to_fp16(1.0).val);
+	EXPECT_DOUBLE_EQ(1.0, fp16_to_fp32(make_fp16(0x3c00)));
 
-	EXPECT_EQ(0x3555, fp64_to_fp16(1.0 / 3.0));
-	EXPECT_DOUBLE_EQ(0.333251953125, fp16_to_fp64(0x3555));
+	EXPECT_EQ(0x3555, fp32_to_fp16(1.0 / 3.0).val);
+	EXPECT_DOUBLE_EQ(0.333251953125, fp16_to_fp32(make_fp16(0x3555)));
 }
 
-TEST(FP16Test, NaN) {
-	EXPECT_EQ(0xfe00, fp64_to_fp16(0.0 / 0.0));
-	EXPECT_TRUE(isnan(fp16_to_fp64(0xfe00)));
+TEST(FP16Test, RoundToNearestEven) {
+	ASSERT_DOUBLE_EQ(1.0, fp16_to_fp32(make_fp16(0x3c00)));
+
+	double x0 = fp16_to_fp32(make_fp16(0x3c00));
+	double x1 = fp16_to_fp32(make_fp16(0x3c01));
+	double x2 = fp16_to_fp32(make_fp16(0x3c02));
+	double x3 = fp16_to_fp32(make_fp16(0x3c03));
+	double x4 = fp16_to_fp32(make_fp16(0x3c04));
+
+	EXPECT_EQ(0x3c00, fp32_to_fp16(0.5 * (x0 + x1)).val);
+	EXPECT_EQ(0x3c02, fp32_to_fp16(0.5 * (x1 + x2)).val);
+	EXPECT_EQ(0x3c02, fp32_to_fp16(0.5 * (x2 + x3)).val);
+	EXPECT_EQ(0x3c04, fp32_to_fp16(0.5 * (x3 + x4)).val);
 }
 
 union fp64 {
 	double f;
 	unsigned long long ll;
 };
+
+#ifdef __F16C__
 union fp32 {
 	float f;
 	unsigned int u;
 };
+#endif
+
+TEST(FP16Test, NaN) {
+	// Ignore the sign bit.
+	EXPECT_EQ(0x7e00, fp32_to_fp16(0.0 / 0.0).val & 0x7fff);
+	EXPECT_TRUE(isnan(fp16_to_fp32(make_fp16(0xfe00))));
+
+	fp32 borderline_inf;
+	borderline_inf.u = 0x7f800000ull;
+	fp32 borderline_nan;
+	borderline_nan.u = 0x7f800001ull;
+
+	ASSERT_FALSE(isfinite(borderline_inf.f));
+	ASSERT_FALSE(isnan(borderline_inf.f));
+
+	ASSERT_FALSE(isfinite(borderline_nan.f));
+	ASSERT_TRUE(isnan(borderline_nan.f));
+
+	double borderline_inf_roundtrip = fp16_to_fp32(fp32_to_fp16(borderline_inf.f));
+	double borderline_nan_roundtrip = fp16_to_fp32(fp32_to_fp16(borderline_nan.f));
+
+	EXPECT_FALSE(isfinite(borderline_inf_roundtrip));
+	EXPECT_FALSE(isnan(borderline_inf_roundtrip));
 
-// Randomly test a large number of fp64 -> fp32 conversions, comparing
-// against the FPU.
-TEST(FP16Test, FP32ReferenceDownconvert) {
-	srand(12345);
-
-	for (int i = 0; i < 1000000; ++i) {
-		unsigned r1 = rand();
-		unsigned r2 = rand();
-		unsigned r3 = rand();
-		union fp64 src;
-		union fp32 reference, result;
-
-		src.ll = (((unsigned long long)r1) << 33) ^ ((unsigned long long)r2 << 16) ^ r3;
-		reference.f = float(src.f);
-		result.u = fp64_to_fp32(src.f);
-
-		EXPECT_EQ(isnan(result.f), isnan(reference.f));
-		if (!isnan(result.f)) {
-			EXPECT_EQ(result.u, reference.u)
-			    << src.f << " got rounded to " << result.u << " (" << result.f << ")";
-		}
-	}
+	EXPECT_FALSE(isfinite(borderline_nan_roundtrip));
+	EXPECT_TRUE(isnan(borderline_nan_roundtrip));
 }
 
-// Randomly test a large number of fp32 -> fp64 conversions, comparing
-// against the FPU.
-TEST(FP16Test, FP32ReferenceUpconvert) {
-	srand(12345);
-
-	for (int i = 0; i < 1000000; ++i) {
-		unsigned r1 = rand();
-		unsigned r2 = rand();
-		union fp32 src;
-		union fp64 reference, result;
-
-		src.u = ((unsigned long long)r1 << 16) ^ r2;
-		reference.f = double(src.f);
-		result.f = fp32_to_fp64(src.u);
-
-		EXPECT_EQ(isnan(result.f), isnan(reference.f));
-		if (!isnan(result.f)) {
-			EXPECT_EQ(result.ll, reference.ll)
-			    << src.f << " got converted to " << result.ll << " (" << result.f << ")";
-		}
-	}
+TEST(FP16Test, Denormals) {
+	const double smallest_fp16_denormal = 5.9604644775390625e-08;
+	EXPECT_EQ(0x0001, fp32_to_fp16(smallest_fp16_denormal).val);
+	EXPECT_EQ(0x0000, fp32_to_fp16(0.5 * smallest_fp16_denormal).val);  // Round-to-even.
+	EXPECT_EQ(0x0001, fp32_to_fp16(0.51 * smallest_fp16_denormal).val);
+	EXPECT_EQ(0x0002, fp32_to_fp16(1.5 * smallest_fp16_denormal).val);
+
+	const double smallest_fp16_non_denormal = 6.103515625e-05;
+	EXPECT_EQ(0x0400, fp32_to_fp16(smallest_fp16_non_denormal).val);
+	EXPECT_EQ(0x0400, fp32_to_fp16(smallest_fp16_non_denormal - 0.5 * smallest_fp16_denormal).val);  // Round-to-even.
+	EXPECT_EQ(0x03ff, fp32_to_fp16(smallest_fp16_non_denormal - smallest_fp16_denormal).val);
 }
 
 }  // namespace movit