From 4d6528a3d6bf3821c216c68f99170e2faab5d63c Mon Sep 17 00:00:00 2001 From: Greg Sanders Date: Fri, 12 Jan 2024 11:17:47 -0500 Subject: [PATCH] fuzz: fuzz diagram creation and comparison Co-authored-by: Suhas Daftuar Co-authored-by: Pieter Wuille --- src/Makefile.test.include | 1 + src/test/fuzz/feeratediagram.cpp | 119 +++++++++++++++++++++++++++++++ 2 files changed, 120 insertions(+) create mode 100644 src/test/fuzz/feeratediagram.cpp diff --git a/src/Makefile.test.include b/src/Makefile.test.include index 83ea4b139ca..2e475f08039 100644 --- a/src/Makefile.test.include +++ b/src/Makefile.test.include @@ -315,6 +315,7 @@ test_fuzz_fuzz_SOURCES = \ test/fuzz/deserialize.cpp \ test/fuzz/eval_script.cpp \ test/fuzz/fee_rate.cpp \ + test/fuzz/feeratediagram.cpp \ test/fuzz/fees.cpp \ test/fuzz/flatfile.cpp \ test/fuzz/float.cpp \ diff --git a/src/test/fuzz/feeratediagram.cpp b/src/test/fuzz/feeratediagram.cpp new file mode 100644 index 00000000000..6d710093cbb --- /dev/null +++ b/src/test/fuzz/feeratediagram.cpp @@ -0,0 +1,119 @@ +// Copyright (c) 2023 The Bitcoin Core developers +// Distributed under the MIT software license, see the accompanying +// file COPYING or http://www.opensource.org/licenses/mit-license.php. + +#include + +#include + +#include +#include + +#include +#include + +#include + +namespace { + +/** Evaluate a diagram at a specific size, returning the fee as a fraction. + * + * Fees in diagram cannot exceed 2^32, as the returned evaluation could overflow + * the FeeFrac::fee field in the result. */ +FeeFrac EvaluateDiagram(int32_t size, Span diagram) +{ + assert(diagram.size() > 0); + unsigned not_above = 0; + unsigned not_below = diagram.size() - 1; + // If outside the range of diagram, extend begin/end. + if (size < diagram[not_above].size) return {diagram[not_above].fee, 1}; + if (size > diagram[not_below].size) return {diagram[not_below].fee, 1}; + // Perform bisection search to locate the diagram segment that size is in. + while (not_below > not_above + 1) { + unsigned mid = (not_below + not_above) / 2; + if (diagram[mid].size <= size) not_above = mid; + if (diagram[mid].size >= size) not_below = mid; + } + // If the size matches a transition point between segments, return its fee. + if (not_below == not_above) return {diagram[not_below].fee, 1}; + // Otherwise, interpolate. + auto dir_coef = diagram[not_below] - diagram[not_above]; + assert(dir_coef.size > 0); + // Let A = diagram[not_above] and B = diagram[not_below] + const auto& point_a = diagram[not_above]; + // We want to return: + // A.fee + (B.fee - A.fee) / (B.size - A.size) * (size - A.size) + // = A.fee + dir_coef.fee / dir_coef.size * (size - A.size) + // = (A.fee * dir_coef.size + dir_coef.fee * (size - A.size)) / dir_coef.size + assert(size >= point_a.size); + return {point_a.fee * dir_coef.size + dir_coef.fee * (size - point_a.size), dir_coef.size}; +} + +std::weak_ordering CompareFeeFracWithDiagram(const FeeFrac& ff, Span diagram) +{ + return FeeRateCompare(FeeFrac{ff.fee, 1}, EvaluateDiagram(ff.size, diagram)); +} + +std::partial_ordering CompareDiagrams(Span dia1, Span dia2) +{ + bool all_ge = true; + bool all_le = true; + for (const auto p1 : dia1) { + auto cmp = CompareFeeFracWithDiagram(p1, dia2); + if (std::is_lt(cmp)) all_ge = false; + if (std::is_gt(cmp)) all_le = false; + } + for (const auto p2 : dia2) { + auto cmp = CompareFeeFracWithDiagram(p2, dia1); + if (std::is_lt(cmp)) all_le = false; + if (std::is_gt(cmp)) all_ge = false; + } + if (all_ge && all_le) return std::partial_ordering::equivalent; + if (all_ge && !all_le) return std::partial_ordering::greater; + if (!all_ge && all_le) return std::partial_ordering::less; + return std::partial_ordering::unordered; +} + +void PopulateChunks(FuzzedDataProvider& fuzzed_data_provider, std::vector& chunks) +{ + chunks.clear(); + + LIMITED_WHILE(fuzzed_data_provider.ConsumeBool(), 50) + { + chunks.emplace_back(fuzzed_data_provider.ConsumeIntegralInRange(INT32_MIN>>1, INT32_MAX>>1), fuzzed_data_provider.ConsumeIntegralInRange(1, 1000000)); + } + return; +} + +} // namespace + +FUZZ_TARGET(build_and_compare_feerate_diagram) +{ + // Generate a random set of chunks + FuzzedDataProvider fuzzed_data_provider(buffer.data(), buffer.size()); + std::vector chunks1, chunks2; + FeeFrac empty{0, 0}; + + PopulateChunks(fuzzed_data_provider, chunks1); + PopulateChunks(fuzzed_data_provider, chunks2); + + std::vector diagram1{BuildDiagramFromChunks(chunks1)}; + std::vector diagram2{BuildDiagramFromChunks(chunks2)}; + + assert(diagram1.front() == empty); + assert(diagram2.front() == empty); + + auto real = CompareFeerateDiagram(diagram1, diagram2); + auto sim = CompareDiagrams(diagram1, diagram2); + assert(real == sim); + + // Do explicit evaluation at up to 1000 points, and verify consistency with the result. + LIMITED_WHILE(fuzzed_data_provider.remaining_bytes(), 1000) { + int32_t size = fuzzed_data_provider.ConsumeIntegralInRange(0, diagram2.back().size); + auto eval1 = EvaluateDiagram(size, diagram1); + auto eval2 = EvaluateDiagram(size, diagram2); + auto cmp = FeeRateCompare(eval1, eval2); + if (std::is_lt(cmp)) assert(!std::is_gt(real)); + if (std::is_gt(cmp)) assert(!std::is_lt(real)); + } +}