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Merge bitcoin/bitcoin#29192: Weaken serfloat tests
6e873df serfloat: improve/simplify tests (Pieter Wuille) b45f1f5 serfloat: do not test encode(bits)=bits anymore (Pieter Wuille) Pull request description: Closes #28941. Our current tests for serfloat verify two distinct properties: 1. Whether they roundtrip `double`->`uint64_t`->`double` (excluding NaN values) on all systems. 2. Whether on systems with a typical floating point unit that encoding matches the hardware representation, as before v22.0, we would dump the hardware representation directly to disk and we wanted to retain compatibility with that. #28941 seems to show that the second property doesn't always hold, but just for "subnormal" numbers (below $2^{-1021}$). Since we don't care about encoding these numbers, we could exclude such subnormal numbers from the hardware-identical representation test, but this PR goes further and just drops the second property entirely, as I don't think we care about edge-case compatibility with pre-v22.0 code for fee_estimates.dat (the only place it is used). ACKs for top commit: glozow: ACK 6e873df fanquake: ACK 6e873df - It's not as much of a priority, but I think we could still backport this. Tree-SHA512: e18ceee0753a7ee7e999fdfa10b014dc5bb67b6ef79522a0f8c76b889adcfa785772fc26ed7559bcb5a09a9938e243bb54eedd9549bc59080a2c8090155e2267
2 parents 8e95a9c + 6e873df commit 479ecc0

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‎src/test/serfloat_tests.cpp‎

Lines changed: 69 additions & 47 deletions
Original file line numberDiff line numberDiff line change
@@ -37,6 +37,7 @@ uint64_t TestDouble(double f) {
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} // namespace
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BOOST_AUTO_TEST_CASE(double_serfloat_tests) {
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// Test specific values against their expected encoding.
4041
BOOST_CHECK_EQUAL(TestDouble(0.0), 0U);
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BOOST_CHECK_EQUAL(TestDouble(-0.0), 0x8000000000000000);
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BOOST_CHECK_EQUAL(TestDouble(std::numeric_limits<double>::infinity()), 0x7ff0000000000000U);
@@ -46,55 +47,76 @@ BOOST_AUTO_TEST_CASE(double_serfloat_tests) {
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BOOST_CHECK_EQUAL(TestDouble(2.0), 0x4000000000000000ULL);
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BOOST_CHECK_EQUAL(TestDouble(4.0), 0x4010000000000000ULL);
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BOOST_CHECK_EQUAL(TestDouble(785.066650390625), 0x4088888880000000ULL);
50+
BOOST_CHECK_EQUAL(TestDouble(3.7243058682384174), 0x400dcb60e0031440);
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BOOST_CHECK_EQUAL(TestDouble(91.64070592566159), 0x4056e901536d447a);
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BOOST_CHECK_EQUAL(TestDouble(-98.63087668642575), 0xc058a860489c007a);
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BOOST_CHECK_EQUAL(TestDouble(4.908737756962054), 0x4013a28c268b2b70);
54+
BOOST_CHECK_EQUAL(TestDouble(77.9247330021754), 0x40537b2ed3547804);
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BOOST_CHECK_EQUAL(TestDouble(40.24732825357566), 0x40441fa873c43dfc);
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BOOST_CHECK_EQUAL(TestDouble(71.39395607929222), 0x4051d936938f27b6);
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BOOST_CHECK_EQUAL(TestDouble(58.80100710817612), 0x404d668766a2bd70);
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BOOST_CHECK_EQUAL(TestDouble(-30.10665786964975), 0xc03e1b4dee1e01b8);
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BOOST_CHECK_EQUAL(TestDouble(60.15231509068704), 0x404e137f0f969814);
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BOOST_CHECK_EQUAL(TestDouble(-48.15848711335961), 0xc04814494e445bc6);
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BOOST_CHECK_EQUAL(TestDouble(26.68450101125353), 0x403aaf3b755169b0);
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BOOST_CHECK_EQUAL(TestDouble(-65.72071986604303), 0xc0506e2046378ede);
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BOOST_CHECK_EQUAL(TestDouble(17.95575825512381), 0x4031f4ac92b0a388);
64+
BOOST_CHECK_EQUAL(TestDouble(-35.27171863226279), 0xc041a2c7ad17a42a);
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BOOST_CHECK_EQUAL(TestDouble(-8.58810329425124), 0xc0212d1bdffef538);
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BOOST_CHECK_EQUAL(TestDouble(88.51393044338977), 0x405620e43c83b1c8);
67+
BOOST_CHECK_EQUAL(TestDouble(48.07224932612732), 0x4048093f77466ffc);
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BOOST_CHECK_EQUAL(TestDouble(9.867348871395659e+117), 0x586f4daeb2459b9f);
69+
BOOST_CHECK_EQUAL(TestDouble(-1.5166424385129721e+206), 0xeabe3bbc484bd458);
70+
BOOST_CHECK_EQUAL(TestDouble(-8.585156555624594e-275), 0x8707c76eee012429);
71+
BOOST_CHECK_EQUAL(TestDouble(2.2794371091628822e+113), 0x5777b2184458f4ee);
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BOOST_CHECK_EQUAL(TestDouble(-1.1290476594131867e+163), 0xe1c91893d3488bb0);
73+
BOOST_CHECK_EQUAL(TestDouble(9.143848423979275e-246), 0x0d0ff76e5f2620a3);
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BOOST_CHECK_EQUAL(TestDouble(-2.8366718125941117e+81), 0xd0d7ec7e754b394a);
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BOOST_CHECK_EQUAL(TestDouble(-1.2754409481684012e+229), 0xef80d32f8ec55342);
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BOOST_CHECK_EQUAL(TestDouble(6.000577060053642e-186), 0x197a1be7c8209b6a);
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BOOST_CHECK_EQUAL(TestDouble(2.0839423284378986e-302), 0x014c94f8689cb0a5);
78+
BOOST_CHECK_EQUAL(TestDouble(-1.422140051483753e+259), 0xf5bd99271d04bb35);
79+
BOOST_CHECK_EQUAL(TestDouble(-1.0593973991188853e+46), 0xc97db0cdb72d1046);
80+
BOOST_CHECK_EQUAL(TestDouble(2.62945125875249e+190), 0x67779b36366c993b);
81+
BOOST_CHECK_EQUAL(TestDouble(-2.920377657275094e+115), 0xd7e7b7b45908e23b);
82+
BOOST_CHECK_EQUAL(TestDouble(9.790289014855851e-118), 0x27a3c031cc428bcc);
83+
BOOST_CHECK_EQUAL(TestDouble(-4.629317182034961e-114), 0xa866ccf0b753705a);
84+
BOOST_CHECK_EQUAL(TestDouble(-1.7674605603846528e+279), 0xf9e8ed383ffc3e25);
85+
BOOST_CHECK_EQUAL(TestDouble(2.5308171727712605e+120), 0x58ef5cd55f0ec997);
86+
BOOST_CHECK_EQUAL(TestDouble(-1.05034156412799e+54), 0xcb25eea1b9350fa0);
4987

50-
// Roundtrip test on IEC559-compatible systems
51-
if (std::numeric_limits<double>::is_iec559) {
52-
BOOST_CHECK_EQUAL(sizeof(double), 8U);
53-
BOOST_CHECK_EQUAL(sizeof(uint64_t), 8U);
54-
// Test extreme values
55-
TestDouble(std::numeric_limits<double>::min());
56-
TestDouble(-std::numeric_limits<double>::min());
57-
TestDouble(std::numeric_limits<double>::max());
58-
TestDouble(-std::numeric_limits<double>::max());
59-
TestDouble(std::numeric_limits<double>::lowest());
60-
TestDouble(-std::numeric_limits<double>::lowest());
61-
TestDouble(std::numeric_limits<double>::quiet_NaN());
62-
TestDouble(-std::numeric_limits<double>::quiet_NaN());
63-
TestDouble(std::numeric_limits<double>::signaling_NaN());
64-
TestDouble(-std::numeric_limits<double>::signaling_NaN());
65-
TestDouble(std::numeric_limits<double>::denorm_min());
66-
TestDouble(-std::numeric_limits<double>::denorm_min());
67-
// Test exact encoding: on currently supported platforms, EncodeDouble
68-
// should produce exactly the same as the in-memory representation for non-NaN.
69-
for (int j = 0; j < 1000; ++j) {
70-
// Iterate over 9 specific bits exhaustively; the others are chosen randomly.
71-
// These specific bits are the sign bit, and the 2 top and bottom bits of
72-
// exponent and mantissa in the IEEE754 binary64 format.
73-
for (int x = 0; x < 512; ++x) {
74-
uint64_t v = InsecureRandBits(64);
75-
v &= ~(uint64_t{1} << 0);
76-
if (x & 1) v |= (uint64_t{1} << 0);
77-
v &= ~(uint64_t{1} << 1);
78-
if (x & 2) v |= (uint64_t{1} << 1);
79-
v &= ~(uint64_t{1} << 50);
80-
if (x & 4) v |= (uint64_t{1} << 50);
81-
v &= ~(uint64_t{1} << 51);
82-
if (x & 8) v |= (uint64_t{1} << 51);
83-
v &= ~(uint64_t{1} << 52);
84-
if (x & 16) v |= (uint64_t{1} << 52);
85-
v &= ~(uint64_t{1} << 53);
86-
if (x & 32) v |= (uint64_t{1} << 53);
87-
v &= ~(uint64_t{1} << 61);
88-
if (x & 64) v |= (uint64_t{1} << 61);
89-
v &= ~(uint64_t{1} << 62);
90-
if (x & 128) v |= (uint64_t{1} << 62);
91-
v &= ~(uint64_t{1} << 63);
92-
if (x & 256) v |= (uint64_t{1} << 63);
93-
double f;
94-
memcpy(&f, &v, 8);
95-
uint64_t v2 = TestDouble(f);
96-
if (!std::isnan(f)) BOOST_CHECK_EQUAL(v, v2);
88+
// Test extreme values
89+
BOOST_CHECK_EQUAL(TestDouble(std::numeric_limits<double>::min()), 0x10000000000000);
90+
BOOST_CHECK_EQUAL(TestDouble(-std::numeric_limits<double>::min()), 0x8010000000000000);
91+
BOOST_CHECK_EQUAL(TestDouble(std::numeric_limits<double>::max()), 0x7fefffffffffffff);
92+
BOOST_CHECK_EQUAL(TestDouble(-std::numeric_limits<double>::max()), 0xffefffffffffffff);
93+
BOOST_CHECK_EQUAL(TestDouble(std::numeric_limits<double>::lowest()), 0xffefffffffffffff);
94+
BOOST_CHECK_EQUAL(TestDouble(-std::numeric_limits<double>::lowest()), 0x7fefffffffffffff);
95+
BOOST_CHECK_EQUAL(TestDouble(std::numeric_limits<double>::denorm_min()), 0x1);
96+
BOOST_CHECK_EQUAL(TestDouble(-std::numeric_limits<double>::denorm_min()), 0x8000000000000001);
97+
// Note that all NaNs are encoded the same way.
98+
BOOST_CHECK_EQUAL(TestDouble(std::numeric_limits<double>::quiet_NaN()), 0x7ff8000000000000);
99+
BOOST_CHECK_EQUAL(TestDouble(-std::numeric_limits<double>::quiet_NaN()), 0x7ff8000000000000);
100+
BOOST_CHECK_EQUAL(TestDouble(std::numeric_limits<double>::signaling_NaN()), 0x7ff8000000000000);
101+
BOOST_CHECK_EQUAL(TestDouble(-std::numeric_limits<double>::signaling_NaN()), 0x7ff8000000000000);
102+
103+
// Construct doubles to test from the encoding.
104+
static_assert(sizeof(double) == 8);
105+
static_assert(sizeof(uint64_t) == 8);
106+
for (int j = 0; j < 1000; ++j) {
107+
// Iterate over 9 specific bits exhaustively; the others are chosen randomly.
108+
// These specific bits are the sign bit, and the 2 top and bottom bits of
109+
// exponent and mantissa in the IEEE754 binary64 format.
110+
for (int x = 0; x < 512; ++x) {
111+
uint64_t v = InsecureRandBits(64);
112+
int x_pos = 0;
113+
for (int v_pos : {0, 1, 50, 51, 52, 53, 61, 62, 63}) {
114+
v &= ~(uint64_t{1} << v_pos);
115+
if ((x >> (x_pos++)) & 1) v |= (uint64_t{1} << v_pos);
97116
}
117+
double f;
118+
memcpy(&f, &v, 8);
119+
TestDouble(f);
98120
}
99121
}
100122
}

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