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src/pow/test/aserti32d_tests.cpp
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// Copyright (c) 2020 The Bitcoin Core developers | |||||
// Distributed under the MIT/X11 software license, see the accompanying | |||||
// file COPYING or http://www.opensource.org/licenses/mit-license.php. | |||||
#include <pow/aserti32d.h> | |||||
#include <chain.h> | |||||
#include <chainparams.h> | |||||
#include <config.h> | |||||
#include <test/util/setup_common.h> | |||||
#include <boost/test/unit_test.hpp> | |||||
#include <cmath> | |||||
BOOST_FIXTURE_TEST_SUITE(aserti32d_tests, BasicTestingSetup) | |||||
static CBlockIndex GetBlockIndex(CBlockIndex *pindexPrev, int64_t nTimeInterval, | |||||
uint32_t nBits) { | |||||
CBlockIndex block; | |||||
block.pprev = pindexPrev; | |||||
block.nHeight = pindexPrev->nHeight + 1; | |||||
block.nTime = pindexPrev->nTime + nTimeInterval; | |||||
block.nBits = nBits; | |||||
block.nChainWork = pindexPrev->nChainWork + GetBlockProof(block); | |||||
return block; | |||||
} | |||||
static double TargetFromBits(const uint32_t nBits) { | |||||
return (nBits & 0xff'ff'ff) * pow(256, (nBits >> 24) - 3); | |||||
} | |||||
static double | |||||
GetASERTApproximationError(const CBlockIndex *pindexPrev, | |||||
const uint32_t finalBits, | |||||
const CBlockIndex *pindexReferenceBlock) { | |||||
const int64_t nHeightDiff = | |||||
pindexPrev->nHeight - pindexReferenceBlock->nHeight; | |||||
const int64_t nTimeDiff = pindexPrev->nTime - pindexReferenceBlock->nTime; | |||||
const uint32_t initialBits = pindexReferenceBlock->nBits; | |||||
BOOST_CHECK(nHeightDiff >= 0); | |||||
double dInitialPow = TargetFromBits(initialBits); | |||||
double dFinalPow = TargetFromBits(finalBits); | |||||
double dExponent = | |||||
double(nTimeDiff - nHeightDiff * 600) / double(2 * 24 * 3600); | |||||
double dTarget = dInitialPow * pow(2, dExponent); | |||||
return (dFinalPow - dTarget) / dTarget; | |||||
} | |||||
BOOST_AUTO_TEST_CASE(asert_difficulty_test) { | |||||
DummyConfig config(CBaseChainParams::MAIN); | |||||
std::vector<CBlockIndex> blocks(3000 + 2 * 24 * 3600); | |||||
const Consensus::Params ¶ms = config.GetChainParams().GetConsensus(); | |||||
const arith_uint256 powLimit = UintToArith256(params.powLimit); | |||||
arith_uint256 currentPow = powLimit >> 3; | |||||
uint32_t initialBits = currentPow.GetCompact(); | |||||
double dMaxErr = 0.0001166792656486; | |||||
// Genesis block, also ASERT reference block in this test case. | |||||
blocks[0] = CBlockIndex(); | |||||
blocks[0].nHeight = 0; | |||||
blocks[0].nTime = 1269211443; | |||||
blocks[0].nBits = initialBits; | |||||
blocks[0].nChainWork = GetBlockProof(blocks[0]); | |||||
// Block counter. | |||||
size_t i; | |||||
// Pile up some blocks every 10 mins to establish some history. | |||||
for (i = 1; i < 150; i++) { | |||||
blocks[i] = GetBlockIndex(&blocks[i - 1], 600, initialBits); | |||||
BOOST_CHECK_EQUAL(blocks[i].nBits, initialBits); | |||||
} | |||||
CBlockHeader blkHeaderDummy; | |||||
uint32_t nBits = GetNextASERTWorkRequired(&blocks[i - 1], &blkHeaderDummy, | |||||
params, &blocks[1]); | |||||
BOOST_CHECK_EQUAL(nBits, initialBits); | |||||
// Difficulty stays the same as long as we produce a block every 10 mins. | |||||
for (size_t j = 0; j < 10; i++, j++) { | |||||
blocks[i] = GetBlockIndex(&blocks[i - 1], 600, nBits); | |||||
BOOST_CHECK_EQUAL(GetNextASERTWorkRequired(&blocks[i], &blkHeaderDummy, | |||||
params, &blocks[1]), | |||||
nBits); | |||||
} | |||||
// If we add a two blocks whose solvetimes together add up to 1200s, | |||||
// then the next block's target should be the same as the one before these | |||||
// blocks (at this point, equal to initialBits). | |||||
blocks[i] = GetBlockIndex(&blocks[i - 1], 300, nBits); | |||||
nBits = GetNextASERTWorkRequired(&blocks[i++], &blkHeaderDummy, params, | |||||
&blocks[1]); | |||||
BOOST_CHECK(fabs(GetASERTApproximationError(&blocks[i - 1], nBits, | |||||
&blocks[0])) < dMaxErr); | |||||
blocks[i] = GetBlockIndex(&blocks[i - 1], 900, nBits); | |||||
nBits = GetNextASERTWorkRequired(&blocks[i++], &blkHeaderDummy, params, | |||||
&blocks[1]); | |||||
BOOST_CHECK(fabs(GetASERTApproximationError(&blocks[i - 1], nBits, | |||||
&blocks[1])) < dMaxErr); | |||||
BOOST_CHECK_EQUAL(nBits, initialBits); | |||||
BOOST_CHECK(nBits != blocks[i - 1].nBits); | |||||
// Same in reverse - this time slower block first, followed by faster block. | |||||
blocks[i] = GetBlockIndex(&blocks[i - 1], 900, nBits); | |||||
nBits = GetNextASERTWorkRequired(&blocks[i++], &blkHeaderDummy, params, | |||||
&blocks[1]); | |||||
BOOST_CHECK(fabs(GetASERTApproximationError(&blocks[i - 1], nBits, | |||||
&blocks[1])) < dMaxErr); | |||||
blocks[i] = GetBlockIndex(&blocks[i - 1], 300, nBits); | |||||
nBits = GetNextASERTWorkRequired(&blocks[i++], &blkHeaderDummy, params, | |||||
&blocks[1]); | |||||
BOOST_CHECK(fabs(GetASERTApproximationError(&blocks[i - 1], nBits, | |||||
&blocks[1])) < dMaxErr); | |||||
BOOST_CHECK_EQUAL(nBits, initialBits); | |||||
BOOST_CHECK(nBits != blocks[i - 1].nBits); | |||||
// Jumping forward 2 days should double the target (halve the difficulty) | |||||
blocks[i] = GetBlockIndex(&blocks[i - 1], 600 + 2 * 24 * 3600, nBits); | |||||
nBits = GetNextASERTWorkRequired(&blocks[i++], &blkHeaderDummy, params, | |||||
&blocks[1]); | |||||
BOOST_CHECK(fabs(GetASERTApproximationError(&blocks[i - 1], nBits, | |||||
&blocks[1])) < dMaxErr); | |||||
currentPow = arith_uint256().SetCompact(nBits) / 2; | |||||
BOOST_CHECK_EQUAL(currentPow.GetCompact(), initialBits); | |||||
// Iterate over the entire -2*24*3600..+2*24*3600 range to check that our | |||||
// integer approximation: | |||||
// 1. Should be monotonic. | |||||
// 2. Should change target at least once every 8 seconds (worst-case: | |||||
// 15-bit precision on nBits). | |||||
// 3. Should never change target by more than XXXX per 1-second step. | |||||
// 4. Never exceeds dMaxError in absolute error vs a double float | |||||
// calculation. | |||||
// 5. Has almost exactly the dMax and dMin errors we expect for the | |||||
// formula. | |||||
double dMin = 0; | |||||
double dMax = 0; | |||||
double dErr; | |||||
double dMaxStep = 0; | |||||
uint32_t nBitsRingBuffer[8]; | |||||
double dStep = 0; | |||||
blocks[i] = GetBlockIndex(&blocks[i - 1], -2 * 24 * 3600 - 30, nBits); | |||||
for (size_t j = 0; j < 4 * 24 * 3600 + 660; j++) { | |||||
blocks[i].nTime++; | |||||
nBits = GetNextASERTWorkRequired(&blocks[i], &blkHeaderDummy, params, | |||||
&blocks[1]); | |||||
if (j > 8) { | |||||
// 1: Monotonic | |||||
BOOST_CHECK( | |||||
arith_uint256().SetCompact(nBits) >= | |||||
arith_uint256().SetCompact(nBitsRingBuffer[(j - 1) % 8])); | |||||
// 2: Changes at least once every 8 seconds (worst case: nBits = | |||||
// 1d008000 to 1d008001) | |||||
BOOST_CHECK(arith_uint256().SetCompact(nBits) > | |||||
arith_uint256().SetCompact(nBitsRingBuffer[j % 8])); | |||||
// 3: Check 1-sec step size | |||||
dStep = (TargetFromBits(nBits) - | |||||
TargetFromBits(nBitsRingBuffer[(j - 1) % 8])) / | |||||
TargetFromBits(nBits); | |||||
dMaxStep = std::max(dStep, dMaxStep); | |||||
// from nBits = 1d008000 to 1d008001 | |||||
BOOST_CHECK(dStep < 0.0000314812106363); | |||||
} | |||||
nBitsRingBuffer[j % 8] = nBits; | |||||
// 4 and 5: check error vs double precision float calculation | |||||
dErr = GetASERTApproximationError(&blocks[i], nBits, &blocks[1]); | |||||
dMin = std::min(dErr, dMin); | |||||
dMax = std::max(dErr, dMax); | |||||
BOOST_CHECK_MESSAGE( | |||||
fabs(dErr) < dMaxErr, | |||||
strprintf( | |||||
"solveTime: %d\tStep size: %.8f%%\tdErr: %.8f%%\tnBits: %0x\n", | |||||
int64_t(blocks[i].nTime) - blocks[i - 1].nTime, dStep * 100, | |||||
dErr * 100, nBits)); | |||||
} | |||||
const auto failMsg = strprintf( | |||||
"Min error: %16.14f%%\tMax error: %16.14f%%\tMax step: %16.14f%%\n", | |||||
dMin * 100, dMax * 100, dMaxStep * 100); | |||||
BOOST_CHECK_MESSAGE( | |||||
dMin < -0.0001013168981059 && dMin > -0.0001013168981060 && | |||||
dMax > 0.0001166792656485 && dMax < 0.0001166792656486, | |||||
failMsg); | |||||
// Difficulty increases as long as we produce fast blocks | |||||
for (size_t j = 0; j < 100; i++, j++) { | |||||
uint32_t nextBits; | |||||
arith_uint256 currentTarget; | |||||
currentTarget.SetCompact(nBits); | |||||
blocks[i] = GetBlockIndex(&blocks[i - 1], 500, nBits); | |||||
nextBits = GetNextASERTWorkRequired(&blocks[i], &blkHeaderDummy, params, | |||||
&blocks[1]); | |||||
arith_uint256 nextTarget; | |||||
nextTarget.SetCompact(nextBits); | |||||
// Make sure that target is decreased | |||||
BOOST_CHECK(nextTarget <= currentTarget); | |||||
nBits = nextBits; | |||||
} | |||||
} | |||||
// Tests of the CalculateASERT function. | |||||
BOOST_AUTO_TEST_CASE(calculate_asert_test) { | |||||
DummyConfig config(CBaseChainParams::MAIN); | |||||
const Consensus::Params ¶ms = config.GetChainParams().GetConsensus(); | |||||
const int64_t nHalfLife = params.nDAAHalfLife; | |||||
const arith_uint256 powLimit = UintToArith256(params.powLimit); | |||||
arith_uint256 initialTarget = powLimit >> 4; | |||||
int64_t height = 0; | |||||
// The CalculateASERT function uses the absolute ASERT formulation | |||||
// and adds +1 to the height difference that it receives. | |||||
// The time difference passed to it must factor in the difference | |||||
// to the *ancestor* of the reference block. | |||||
// We assume the ancestor is ideally spaced in time before the reference | |||||
// block. | |||||
static const int64_t ancestor_time_diff = 600; | |||||
// Steady | |||||
arith_uint256 nextTarget = | |||||
CalculateASERT(initialTarget, params.nPowTargetSpacing, | |||||
ancestor_time_diff + 600 /* nTimeDiff */, ++height, | |||||
powLimit, nHalfLife); | |||||
BOOST_CHECK(nextTarget == initialTarget); | |||||
// A block that arrives in half the expected time | |||||
nextTarget = CalculateASERT(initialTarget, params.nPowTargetSpacing, | |||||
ancestor_time_diff + 600 + 300, ++height, | |||||
powLimit, nHalfLife); | |||||
BOOST_CHECK(nextTarget < initialTarget); | |||||
// A block that makes up for the shortfall of the previous one, restores the | |||||
// target to initial | |||||
arith_uint256 prevTarget = nextTarget; | |||||
nextTarget = CalculateASERT(initialTarget, params.nPowTargetSpacing, | |||||
ancestor_time_diff + 600 + 300 + 900, ++height, | |||||
powLimit, nHalfLife); | |||||
BOOST_CHECK(nextTarget > prevTarget); | |||||
BOOST_CHECK(nextTarget == initialTarget); | |||||
// Two days ahead of schedule should halve the target (double the | |||||
// difficulty) | |||||
prevTarget = nextTarget; | |||||
nextTarget = CalculateASERT(prevTarget, params.nPowTargetSpacing, | |||||
ancestor_time_diff + 288 * 1200, 288, powLimit, | |||||
nHalfLife); | |||||
BOOST_CHECK(nextTarget == prevTarget * 2); | |||||
// Two days behind schedule should double the target (halve the difficulty) | |||||
prevTarget = nextTarget; | |||||
nextTarget = | |||||
CalculateASERT(prevTarget, params.nPowTargetSpacing, | |||||
ancestor_time_diff + 288 * 0, 288, powLimit, nHalfLife); | |||||
BOOST_CHECK(nextTarget == prevTarget / 2); | |||||
BOOST_CHECK(nextTarget == initialTarget); | |||||
// Ramp up from initialTarget to PowLimit - should only take 4 doublings... | |||||
uint32_t powLimit_nBits = powLimit.GetCompact(); | |||||
uint32_t next_nBits; | |||||
for (size_t k = 0; k < 3; k++) { | |||||
prevTarget = nextTarget; | |||||
nextTarget = CalculateASERT(prevTarget, params.nPowTargetSpacing, | |||||
ancestor_time_diff + 288 * 1200, 288, | |||||
powLimit, nHalfLife); | |||||
BOOST_CHECK(nextTarget == prevTarget * 2); | |||||
BOOST_CHECK(nextTarget < powLimit); | |||||
next_nBits = nextTarget.GetCompact(); | |||||
BOOST_CHECK(next_nBits != powLimit_nBits); | |||||
} | |||||
prevTarget = nextTarget; | |||||
nextTarget = CalculateASERT(prevTarget, params.nPowTargetSpacing, | |||||
ancestor_time_diff + 288 * 1200, 288, powLimit, | |||||
nHalfLife); | |||||
next_nBits = nextTarget.GetCompact(); | |||||
BOOST_CHECK(nextTarget == prevTarget * 2); | |||||
BOOST_CHECK(next_nBits == powLimit_nBits); | |||||
// Fast periods now cannot increase target beyond POW limit, even if we try | |||||
// to overflow nextTarget. prevTarget is a uint256, so 256*2 = 512 days | |||||
// would overflow nextTarget unless CalculateASERT correctly detects this | |||||
// error | |||||
nextTarget = CalculateASERT(prevTarget, params.nPowTargetSpacing, | |||||
ancestor_time_diff + 512 * 144 * 600, 0, | |||||
powLimit, nHalfLife); | |||||
next_nBits = nextTarget.GetCompact(); | |||||
BOOST_CHECK(next_nBits == powLimit_nBits); | |||||
// We also need to watch for underflows on nextTarget. We need to withstand | |||||
// an extra ~446 days worth of blocks. This should bring down a powLimit | |||||
// target to the a minimum target of 1. | |||||
nextTarget = CalculateASERT(powLimit, params.nPowTargetSpacing, 0, | |||||
2 * (256 - 33) * 144, powLimit, nHalfLife); | |||||
next_nBits = nextTarget.GetCompact(); | |||||
BOOST_CHECK_EQUAL(next_nBits, arith_uint256(1).GetCompact()); | |||||
// Define a structure holding parameters to pass to CalculateASERT. | |||||
// We are going to check some expected results against a vector of | |||||
// possible arguments. | |||||
struct calc_params { | |||||
arith_uint256 refTarget; | |||||
int64_t targetSpacing; | |||||
int64_t timeDiff; | |||||
int64_t heightDiff; | |||||
arith_uint256 expectedTarget; | |||||
uint32_t expectednBits; | |||||
}; | |||||
// Define some named input argument values | |||||
const arith_uint256 SINGLE_300_TARGET{ | |||||
"00000000ffb1ffffffffffffffffffffffffffffffffffffffffffffffffffff"}; | |||||
const arith_uint256 FUNNY_REF_TARGET{ | |||||
"000000008000000000000000000fffffffffffffffffffffffffffffffffffff"}; | |||||
// Define our expected input and output values. | |||||
// The timeDiff entries exclude the `ancestor_time_diff` - this is | |||||
// added in the call to CalculateASERT in the test loop. | |||||
const std::vector<calc_params> calculate_args = { | |||||
/* refTarget, targetSpacing, timeDiff, heightDiff, expectedTarget, | |||||
expectednBits */ | |||||
{powLimit, 600, 0, 2 * 144, powLimit >> 1, 0x1c7fffff}, | |||||
{powLimit, 600, 0, 4 * 144, powLimit >> 2, 0x1c3fffff}, | |||||
{powLimit >> 1, 600, 0, 2 * 144, powLimit >> 2, 0x1c3fffff}, | |||||
{powLimit >> 2, 600, 0, 2 * 144, powLimit >> 3, 0x1c1fffff}, | |||||
{powLimit >> 3, 600, 0, 2 * 144, powLimit >> 4, 0x1c0fffff}, | |||||
{powLimit, 600, 0, 2 * (256 - 34) * 144, 3, 0x01030000}, | |||||
{powLimit, 600, 0, 2 * (256 - 34) * 144 + 119, 3, 0x01030000}, | |||||
{powLimit, 600, 0, 2 * (256 - 34) * 144 + 120, 2, 0x01020000}, | |||||
{powLimit, 600, 0, 2 * (256 - 33) * 144 - 1, 2, 0x01020000}, | |||||
// 1 bit less since we do not need to shift to 0 | |||||
{powLimit, 600, 0, 2 * (256 - 33) * 144, 1, 0x01010000}, | |||||
// more will not decrease below 1 | |||||
{powLimit, 600, 0, 2 * (256 - 32) * 144, 1, 0x01010000}, | |||||
{1, 600, 0, 2 * (256 - 32) * 144, 1, 0x01010000}, | |||||
{powLimit, 600, 2 * (512 - 32) * 144, 0, powLimit, powLimit_nBits}, | |||||
{1, 600, (512 - 64) * 144 * 600, 0, powLimit, powLimit_nBits}, | |||||
// clamps to powLimit | |||||
{powLimit, 600, 300, 1, SINGLE_300_TARGET, 0x1d00ffb1}, | |||||
// confuses any attempt to detect overflow by inspecting result | |||||
{FUNNY_REF_TARGET, 600, 600 * 2 * 33 * 144, 0, powLimit, | |||||
powLimit_nBits}, | |||||
}; | |||||
for (auto &v : calculate_args) { | |||||
nextTarget = CalculateASERT(v.refTarget, v.targetSpacing, | |||||
ancestor_time_diff + v.timeDiff, | |||||
v.heightDiff, powLimit, nHalfLife); | |||||
next_nBits = nextTarget.GetCompact(); | |||||
BOOST_CHECK_EQUAL(next_nBits, v.expectednBits); | |||||
BOOST_CHECK(nextTarget == v.expectedTarget); | |||||
} | |||||
} | |||||
BOOST_AUTO_TEST_SUITE_END() |