This is part of the protocol upgrade for 2020-05-15, and in general it
seems to go the direction of "we did this before, lets do this again".
The spec is clear enough, but there is still a lack of questioning and
testing. The problem this attempts to fix has been neutered for years[1].
The spec states:
> The essential idea of SigChecks is to perform counting solely in the
> spending transaction, and count actual executed signature check
> operations.
This, however nobel and logical, ignores that the
check-for-being-too-costly just pulled in a UTXO lookup and the loading
of the output script from the historical chain.
The goal that we protect against CPU over-use may be reached, but the
price is a total system slowdown. You can have multiple CPUs, but the
bus to permanent storage has one, max 2 parallel pipes.
To ensure theHub stays the number one scalable node, I didn't blindly
follow the spec, while making sure that the Hub is correctly going to
follow/reject consensus violations of newly mined blocks.
As a result the implementation in Flowee the Hub:
* does not check sigcheck-counts on historical blocks (more than 1000
blocks in the past).
This may increase the risk of chain-splits ever so slightly, but the cost
of disk-IO would be too high.
* No longer stores the value in the mempool, nor uses it for the
CPU-miner.
* Ties the sigcheck-limits to the user-set block-size-accept-limit.
This is contrary to the spec which mistakenly thinks that BCH has a
max block-size in the consensus rules. The effect is the same, though.
* The per-intput standardness suggestion is not implemented because
standardness checks don't currently fetch the previous outputs and
that would be too expensive to add.
* Standardness rules for the whole transaction are moved to the
mempool-acceptance logic instead. The cost would be too great
otherwise, similar to the previous point.
Again, the effect is the same as likely intented.
---
1) since the intro of the CachingTransactionSignatureChecker
Merkle-block and merkle-tree classes and methods are pretty much stand-
alone and can be moved with no efforts.
Also move the relevent unit test to qtestlib.
We used various ways to enable new features over the last 10 years.
We can remove that legacy code and just set the blockheight.
This cleans up the code quite a bit.
The "UAHF" one used to be "more equal", mostly just because it happened
to be the first.
This makes them all equally equal.
Specifically this removes the special casing and the enum for the 201708
HF (aka BCH fork-point).
We select the right branch now purely based on the historical check-
points.
TomZ