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txgraph: Introduce BlockBuilder interface (feature)

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This interface lets one iterate efficiently over the chunks of the main
graph in a TxGraph, in the same order as CompareMainOrder. Each chunk
can be marked as "included" or "skipped" (and in the latter case,
dependent chunks will be skipped).
This commit is contained in:
Pieter Wuille
2025-03-28 09:58:09 -04:00
parent 883df3648e
commit 394dbe2142
3 changed files with 254 additions and 8 deletions
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120
src/test/fuzz/txgraph.cpp
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@@ -269,6 +269,24 @@ FUZZ_TARGET(txgraph)
sims.reserve(2);
sims.emplace_back(max_count);
/** Struct encapsulating information about a BlockBuilder that's currently live. */
struct BlockBuilderData
{
/** BlockBuilder object from real. */
std::unique_ptr<TxGraph::BlockBuilder> builder;
/** The set of transactions marked as included in *builder. */
SimTxGraph::SetType included;
/** The set of transactions marked as included or skipped in *builder. */
SimTxGraph::SetType done;
/** The last chunk feerate returned by *builder. IsEmpty() if none yet. */
FeePerWeight last_feerate;
BlockBuilderData(std::unique_ptr<TxGraph::BlockBuilder> builder_in) : builder(std::move(builder_in)) {}
};
/** Currently active block builders. */
std::vector<BlockBuilderData> block_builders;
/** Function to pick any Ref (for either sim in sims: from sim.simmap or sim.removed, or the
* empty Ref). */
auto pick_fn = [&]() noexcept -> TxGraph::Ref* {
@@ -342,6 +360,8 @@ FUZZ_TARGET(txgraph)
LIMITED_WHILE(provider.remaining_bytes() > 0, 200) {
// Read a one-byte command.
int command = provider.ConsumeIntegral<uint8_t>();
int orig_command = command;
// Treat the lowest bit of a command as a flag (which selects a variant of some of the
// operations), and the second-lowest bit as a way of selecting main vs. staging, and leave
// the rest of the bits in command.
@@ -349,6 +369,11 @@ FUZZ_TARGET(txgraph)
bool use_main = command & 2;
command >>= 2;
/** Use the bottom 2 bits of command to select an entry in the block_builders vector (if
* any). These use the same bits as alt/use_main, so don't use those in actions below
* where builder_idx is used as well. */
int builder_idx = block_builders.empty() ? -1 : int((orig_command & 3) % block_builders.size());
// Provide convenient aliases for the top simulated graph (main, or staging if it exists),
// one for the simulated graph selected based on use_main (for operations that can operate
// on both graphs), and one that always refers to the main graph.
@@ -359,7 +384,7 @@ FUZZ_TARGET(txgraph)
// Keep decrementing command for each applicable operation, until one is hit. Multiple
// iterations may be necessary.
while (true) {
if (top_sim.GetTransactionCount() < SimTxGraph::MAX_TRANSACTIONS && command-- == 0) {
if ((block_builders.empty() || sims.size() > 1) && top_sim.GetTransactionCount() < SimTxGraph::MAX_TRANSACTIONS && command-- == 0) {
// AddTransaction.
int64_t fee;
int32_t size;
@@ -381,7 +406,7 @@ FUZZ_TARGET(txgraph)
// Move it in place.
*ref_loc = std::move(ref);
break;
} else if (top_sim.GetTransactionCount() + top_sim.removed.size() > 1 && command-- == 0) {
} else if ((block_builders.empty() || sims.size() > 1) && top_sim.GetTransactionCount() + top_sim.removed.size() > 1 && command-- == 0) {
// AddDependency.
auto par = pick_fn();
auto chl = pick_fn();
@@ -395,7 +420,7 @@ FUZZ_TARGET(txgraph)
top_sim.AddDependency(par, chl);
real->AddDependency(*par, *chl);
break;
} else if (top_sim.removed.size() < 100 && command-- == 0) {
} else if ((block_builders.empty() || sims.size() > 1) && top_sim.removed.size() < 100 && command-- == 0) {
// RemoveTransaction. Either all its ancestors or all its descendants are also
// removed (if any), to make sure TxGraph's reordering of removals and dependencies
// has no effect.
@@ -425,7 +450,7 @@ FUZZ_TARGET(txgraph)
}
sel_sim.removed.pop_back();
break;
} else if (command-- == 0) {
} else if (block_builders.empty() && command-- == 0) {
// ~Ref (of any transaction).
std::vector<TxGraph::Ref*> to_destroy;
to_destroy.push_back(pick_fn());
@@ -447,7 +472,7 @@ FUZZ_TARGET(txgraph)
}
}
break;
} else if (command-- == 0) {
} else if (block_builders.empty() && command-- == 0) {
// SetTransactionFee.
int64_t fee;
if (alt) {
@@ -578,7 +603,7 @@ FUZZ_TARGET(txgraph)
sims.back().modified = SimTxGraph::SetType{};
real->StartStaging();
break;
} else if (sims.size() > 1 && command-- == 0) {
} else if (block_builders.empty() && sims.size() > 1 && command-- == 0) {
// CommitStaging.
real->CommitStaging();
sims.erase(sims.begin());
@@ -664,6 +689,65 @@ FUZZ_TARGET(txgraph)
assert(FeeRateCompare(real_staged_diagram[i], real_staged_diagram[i - 1]) <= 0);
}
break;
} else if (block_builders.size() < 4 && !main_sim.IsOversized() && command-- == 0) {
// GetBlockBuilder.
block_builders.emplace_back(real->GetBlockBuilder());
break;
} else if (!block_builders.empty() && command-- == 0) {
// ~BlockBuilder.
block_builders.erase(block_builders.begin() + builder_idx);
break;
} else if (!block_builders.empty() && command-- == 0) {
// BlockBuilder::GetCurrentChunk, followed by Include/Skip.
auto& builder_data = block_builders[builder_idx];
auto new_included = builder_data.included;
auto new_done = builder_data.done;
auto chunk = builder_data.builder->GetCurrentChunk();
if (chunk) {
// Chunk feerates must be monotonously decreasing.
if (!builder_data.last_feerate.IsEmpty()) {
assert(!(chunk->second >> builder_data.last_feerate));
}
builder_data.last_feerate = chunk->second;
// Verify the contents of GetCurrentChunk.
FeePerWeight sum_feerate;
for (TxGraph::Ref* ref : chunk->first) {
// Each transaction in the chunk must exist in the main graph.
auto simpos = main_sim.Find(ref);
assert(simpos != SimTxGraph::MISSING);
// Verify the claimed chunk feerate.
sum_feerate += main_sim.graph.FeeRate(simpos);
// Make sure no transaction is reported twice.
assert(!new_done[simpos]);
new_done.Set(simpos);
// The concatenation of all included transactions must be topologically valid.
new_included.Set(simpos);
assert(main_sim.graph.Ancestors(simpos).IsSubsetOf(new_included));
}
assert(sum_feerate == chunk->second);
} else {
// When we reach the end, if nothing was skipped, the entire graph should have
// been reported.
if (builder_data.done == builder_data.included) {
assert(builder_data.done.Count() == main_sim.GetTransactionCount());
}
}
// Possibly invoke GetCurrentChunk() again, which should give the same result.
if ((orig_command % 7) >= 5) {
auto chunk2 = builder_data.builder->GetCurrentChunk();
assert(chunk == chunk2);
}
// Skip or include.
if ((orig_command % 5) >= 3) {
// Skip.
builder_data.builder->Skip();
} else {
// Include.
builder_data.builder->Include();
builder_data.included = new_included;
}
builder_data.done = new_done;
break;
}
}
}
@@ -718,6 +802,28 @@ FUZZ_TARGET(txgraph)
}
}
// The same order should be obtained through a BlockBuilder as implied by CompareMainOrder,
// if nothing is skipped.
auto builder = real->GetBlockBuilder();
std::vector<SimTxGraph::Pos> vec_builder;
while (auto chunk = builder->GetCurrentChunk()) {
FeePerWeight sum;
for (TxGraph::Ref* ref : chunk->first) {
// The reported chunk feerate must match the chunk feerate obtained by asking
// it for each of the chunk's transactions individually.
assert(real->GetMainChunkFeerate(*ref) == chunk->second);
// Verify the chunk feerate matches the sum of the reported individual feerates.
sum += real->GetIndividualFeerate(*ref);
// Chunks must contain transactions that exist in the graph.
auto simpos = sims[0].Find(ref);
assert(simpos != SimTxGraph::MISSING);
vec_builder.push_back(simpos);
}
assert(sum == chunk->second);
builder->Include();
}
assert(vec_builder == vec1);
// Check that the implied ordering gives rise to a combined diagram that matches the
// diagram constructed from the individual cluster linearization chunkings.
auto main_real_diagram = get_diagram_fn(/*main_only=*/true);
@@ -848,6 +954,8 @@ FUZZ_TARGET(txgraph)
// Sanity check again (because invoking inspectors may modify internal unobservable state).
real->SanityCheck();
// Kill the block builders.
block_builders.clear();
// Kill the TxGraph object.
real.reset();
// Kill the simulated graphs, with all remaining Refs in it. If any, this verifies that Refs