This allows passing in a fallback order comparator to Linearize(), which
is used as final tiebreak when deciding the order of chunks and
transactions within a chunk, rather than a random tiebreak.
The order of transactions within a chunk becomes:
1. Topology (parents before children)
2. Individual transaction feerate (high to low)
3. Weight (small to large)
4. Fallback (low to high fallback order)
The order of chunks within a cluster becomes:
1. Topology (chunks after their dependencies)
2. Feerate (high to low)
3. Weight (small to large)
4. Max-fallback (chunk with lowest maximum-fallback-tx first)
For now, txgraph passes a naive comparator to Linearize(), which makes
the cluster order deterministic when treating the input transactions as
identified by the DepGraphIndex. However, since DepGraphIndexes are the
result of possibly-randomized operations inside txgraph, this doesn't
actually make txgraph's per-cluster ordering deterministic. That will be
changed in a later commit, by using a txid-based fallback instead.
After the normal optimization process finishes, and finds an optimal
spanning forest, run a second process (while computation budget remains)
to split chunks into minimal equal-feerate chunks.
This replaces the existing LIMO linearization algorithm (which internally uses
ancestor set finding and candidate set finding) with the much more performant
spanning-forest linearization algorithm.
This removes the old candidate-set search algorithm, and several of its tests,
benchmarks, and needed utility code.
The worst case time per cost is similar to the previous algorithm, so
ACCEPTABLE_ITERS is unchanged.
Since cluster_linearize.h does not actually have a Cluster type anymore, it is more
appropriate to rename the index type to DepGraphIndex.
-BEGIN VERIFY SCRIPT-
sed -i 's/Data type to represent transaction indices in clusters./Data type to represent transaction indices in DepGraphs and the clusters they represent./' $(git grep -l 'using ClusterIndex')
sed -i 's|\<ClusterIndex\>|DepGraphIndex|g' $(git grep -l 'ClusterIndex')
-END VERIFY SCRIPT-
This commits introduces support in DepGraph for the transaction positions to be
non-continuous. Specifically, it adds:
* DepGraph::RemoveTransactions which removes 0 or more positions from a DepGraph.
* DepGraph::Positions() to get a set of which positions are in use.
* DepGraph::PositionRange() to get the highest used position in a DepGraph + 1.
In addition, it extends the DepGraphFormatter format to support holes in a
compatible way (it serializes non-holey DepGraphs identically to the old code,
and deserializes them the same way)
This introduces a bespoke fuzzing-focused serialization format for DepGraphs,
and then tests that this format can represent any graph, roundtrips, and then
uses that to test the correctness of DepGraph itself.
This forms the basis for future fuzz tests that need to work with interesting
graphs.
