Both `GetSelectionWaste()` and `ComputeAndSetWaste()` now are part of
`SelectionResult`. Instead of `ComputeAndSetWaste()` being a wrapper for
`GetSelectionWaste()`, we combine them to a new function
`RecalculateWaste()`.
As I was combining the logic of the two functions, I noticed that
`GetSelectionWaste()` was making the odd assumption that the
`change_cost` being set to zero means that no change is created.
However, if we build transactions at a feerate of zero with the
`discard_feerate` also set to zero, we'd organically have a
`change_cost` of zero, even when we create change on a transaction.
This commit cleans up this duplicate meaning of `change_cost` and relies
on `GetChange()` to figure out whether there is change on basis of the
`min_viable_change` and whatever is left after deducting fees.
Since this broke a bunch of tests that relied on the double-meaning of
`change_cost` a bunch of tests had to be fixed.
Given a lot of small amount UTXOs it is possible that the lookahead
indicates sufficient funds, but any combination of them would push us
beyond the current best_weight.
We can estimate a lower bound for the minimal necessary weight to reach
target from the maximal amount and minimal weight in the tail of the
UTXO pool: if adding a number of hypothetical UTXOs of this maximum
amount and minimum weight would not be able to beat `best_weight`, we
can SHIFT to the omission branch, and CUT if the last selected UTXO is
not heavier than the minimum weight of the remainder.
In situations where we have UTXO groups of various weight, we can CUT
rather than SHIFT when we exceeded the max_weight or the best
selection’s weight while the last step was equal to the minimum weight
in the lookahead.
When two successive UTXOs match in effective value and weight, we can
skip the second if the prior is not selected: adding it would create an
equivalent input set to a previously evaluated.
E.g. if we have three UTXOs with effective values {5, 3, 3} of the same
weight each, we want to evaluate
{5, _, _}, {5, 3, _}, {5, 3, 3}, {_, 3, _}, {_, 3, 3},
but skip {5, _, 3}, and {_, _, 3}, because the first 3 is not selected,
and we therefore do not need to evaluate the second 3 at the same
position in the input set.
If we reach the end of the branch, we must SHIFT the previously selected
UTXO group instead.
Introduces a dedicated data structure to track the total
effective_value available in the remaining UTXOs at each index of the
UTXO pool. In contrast to the approach in BnB, this allows us to
immediately jump to a lower index instead of visiting every UTXO to add
back their eff_value to the lookahead.
576bee88fd fuzz: disable BnB when SFFO is enabled (furszy)
05e5ff194c test: add coverage for BnB-SFFO restriction (furszy)
0c5755761c wallet: create tx, log resulting coin selection info (furszy)
5cea25ba79 wallet: skip BnB when SFFO is active (Murch)
Pull request description:
Solves #28918. Coming from https://github.com/bitcoin/bitcoin/issues/28918#issuecomment-1838626406 discussion.
The intention is to decouple only the bugfix relevant commits from #28985, allowing them to be included in the 26.x release. This way, we can avoid disabling the coin selection fuzzing test for an entire release.
Note:
Have introduced few changes to the bug fix commit so that the unit tests pass without the additional burden introduced in #28985.
ACKs for top commit:
josibake:
ACK 576bee88fd
murchandamus:
ACK 576bee88fd
achow101:
ACK 576bee88fd
Tree-SHA512: f5d90eb3f3f524265afe4719495c9bf30f98b9af26cf039f7df5a7db977abae72caa7a3478cdd0ab10cd143bc1662e8fc5286b5bc10fc10f0dd582a45b45c31a
Verify the transaction creation process does not produce
a BnB solution when SFFO is enabled.
This is currently problematic because it could require a
change output. And BnB is specialized on changeless solutions.
Co-authored-by: Andrew Chow <achow101@gmail.com>
Co-authored-by: Murch <murch@murch.one>
Instead of having a separate CCoinControl::SelectExternal function, we
can use the normal CCoinControl::Select function and explicitly use
PreselectedInput::SetTxOut in the caller. The semantics of what an
external input is remains.
When a transaction uses an unconfirmed input, preceding this commit it
would not consider the feerate of the parent transaction. Given a parent
transaction with a lower ancestor feerate, this resulted in the new
transaction's ancestor feerate undershooting the target feerate.
This commit changes how we calculate the effective value of unconfirmed UTXOs.
The effective value of unconfirmed UTXOs is decreased by the fee
necessary to bump its ancestry to the target feerate. This also impacts
the calculation of the waste metric: since the estimate for the current
fee is increased by the bump fees, unconfirmed UTXOs current fees appear less
favorable compared to their unchanged long term fees.
This has one caveat: if multiple UTXOs have overlapping ancestries, each
of their individual estimates will account for bumping all ancestors.
GetSelectionWaste will need to access more context within a selection
result, and so should be a private member function rather than a static
function. It's only use outside of SelectionResult was for tests which
have now been updated to just make a SelectionResult.
Co-authored-by: Murch <murch@murch.one>
1771daa815 [fuzz] Show that SRD budgets for non-dust change (Murch)
941b8c6539 [bug] Increase SRD target by change_fee (Murch)
Pull request description:
I discovered via fuzzing of another coin selection approach that at extremely high feerates SRD may find input sets that lead to transactions without change outputs. This is an unintended outcome since SRD is meant to always produce a transaction with a change output—we use other algorithms to specifically search for changeless solutions.
The issue occurs when the flat allowance of 50,000 ṩ for change is insufficient to pay for the creation of a change output with a non-dust amount, at and above 1,613 ṩ/vB. Increasing the change budget by `change_fee` makes SRD behave as expected at any feerates.
Note: The intermittent failures of `test/functional/interface_usdt_mempool.py` are a known issue: https://github.com/bitcoin/bitcoin/issues/27380
ACKs for top commit:
achow101:
ACK 1771daa815
S3RK:
ACK 1771daa815
Tree-SHA512: 3f36a3e317ef0a711d0e409069c05032bff1d45403023f3728bf73dfd55ddd9e0dc2a9969d4d69fe0a426807ebb0bed1f54abfc05581409bfe42c327acf766d4
I discovered via fuzzing of another coin selection approach that at
extremely high feerates SRD may find input sets that lead to
transactions without change outputs. This is an unintended outcome since
SRD is meant to always produce a transaction with a change output—we use
other algorithms to specifically search for changeless solutions.
The issue occures when the flat allowance of 50,000 ṩ for change is
insufficient to pay for the creation of a change output with a non-dust
amount, at and above 1,613 ṩ/vB. Increasing the change budget by
change_fees makes SRD behave as expected at any feerates.
Since we have a mockable wallet database, we don't really need to be
using BDB or SQLite's in-memory database capabilities. It doesn't really
help us to be using those as we aren't doing anything that requires one
type of db over the other, and will just prefer SQLite if it's
available.
MockableDatabase is suitable for these uses, so use
CreateMockableWalletDatabase to use that.
-BEGIN VERIFY SCRIPT-
sed -i "s/CreateMockWalletDatabase(options)/CreateMockableWalletDatabase()/" $(git grep -l "CreateMockWalletDatabase(options)" -- ":(exclude)src/wallet/walletdb.*")
sed -i "s/CreateMockWalletDatabase/CreateMockableWalletDatabase/" $(git grep -l "CreateMockWalletDatabase" -- ":(exclude)src/wallet/walletdb.*")
-END VERIFY SCRIPT-
The simplest scenario where this is useful is on the 'check_max_weight' unit test
already:
We create 1515 UTXOs with 0.033 BTC each, and 1 UTXO with 50 BTC. Then perform
Coin Selection.
As the selection of the 1515 small UTXOs exceeds the max allowed tx size, the
expectation here is to receive a selection result that only contain the big
UTXO (which is not happening for the reasons stated below).
As knapsack returns a result that exceeds the max allowed transaction size, we
fallback to SRD, which selects coins randomly up until the target is met. So
we end up with a selection result with lot more coins than what is needed.
Optimizes coin selection by performing the "group outputs"
procedure only once, outside the "attempt selection" process.
Avoiding the repeated execution of the 'GroupOutputs' operation
that occurs on each coin eligibility filters (up to 8 of them);
then for every coin vector type plus one for all the coins together.
This also let us not perform coin selection over coin eligibility
filtered groups that don't add new elements.
(because, if the previous round failed, and the subsequent one has
the same coins, then this new round will fail again).
The 'GroupOutputs()' function performs the same
calculations for only-positive and mixed groups,
the only difference is that when we look for
only-positive groups, we discard negative utxos.
So, instead of wasting resources calling GroupOutputs()
for positive-only first, then call it again to include
the negative ones in the result, we can execute
GroupOutputs() only once, including in the response
both group types (positive-only and mixed).
And not hide it inside the `OutputGroup::Insert` method.
This method does not return anything if insertion fails.
We can know before calling `Insert` whether the coin
will be accepted or not.
52f4d567d6 refactor: remove <util/system.h> include from wallet.h (furszy)
6c9b342c30 refactor: wallet, remove global 'ArgsManager' access (furszy)
d8f5fc4462 wallet: set '-walletnotify' script instead of access global args manager (furszy)
3477a28dd3 wallet: set keypool_size instead of access global args manager (furszy)
Pull request description:
Structurally, the wallet class shouldn't access the global `ArgsManager` class, its internal behavior shouldn't be coupled to a global command line args parsing object.
So this PR migrates the only two places where we depend on it: (1) the keypool size, and (2) the "-walletnotify" script. And cleans up the, now unneeded, wallet `ArgsManager` ref member.
Extra note:
In the process of removing the args ref member, discovered and fixed files that were invalidly depending on the wallet header including `util/system.h`.
ACKs for top commit:
achow101:
ACK 52f4d567d6
TheCharlatan:
Re-ACK 52f4d567d6
hebasto:
re-ACK 52f4d567d6
Tree-SHA512: 0cffd99b4dd4864bf618aa45aeaabbef2b6441d27b6dbb03489c4e013330877682ff17b418d07aa25fbe1040bdf2c67d7559bdeb84128c5437bf0e6247719016
f2fc03ec85 refactor: use braced init for integer constants instead of c style casts (Pasta)
Pull request description:
See https://github.com/bitcoin/bitcoin/pull/23810 for more context. This is broken out from that PR, as it is less breaking, and should be trivial to review and merge.
EDIT: Long term, the intention is to remove all C-style casts, as they can dangerously introduce reinterpret_casts. This is one step which removes a number of trivially removable C-style casts
ACKs for top commit:
aureleoules:
ACK f2fc03ec85
Tree-SHA512: 2fd11b92c9147e3f970ec3e130e3b3dce70e707ff02950a8c697d4b111ddcbbfa16915393db20cfc8f384bc76f13241c9b994a187987fcecd16a61f8cc0af14c
76dc547ee7 gui: create tx, launch error dialog if backend throws runtime_error (furszy)
f4d79477ff wallet: coin selection, add duplicated inputs checks (furszy)
0aa065b14e wallet: return accurate error messages from Coin Selection (furszy)
7e8340ab1a wallet: make SelectCoins flow return util::Result (furszy)
e5e147fe97 wallet: refactor eight consecutive 'AttemptSelection' calls into a loop (furszy)
Pull request description:
Work decoupled from #25806, which cleanup and improves the Coin Selection flow further.
Adding the capability to propagate specific error messages from the Coin Selection process to the user.
Instead of always returning the general "Insufficient funds" message which is not always accurate to what happened internally.
Letting us instruct the user how to proceed under certain circumstances.
The following error messages were added:
1) If the selection result exceeds the maximum transaction weight,
we now will return:
-> "The inputs size exceeds the maximum weight. Please try sending
a smaller amount or manually consolidating your wallet's UTXOs".
2) If the user pre-selected inputs and disallowed the automatic coin
selection process (no other inputs are allowed), we now will
return:
-> "The preselected coins total amount does not cover the transaction
target. Please allow other inputs to be automatically selected or include
more coins manually".
3) The double-counted preset inputs during Coin Selection error will now
throw an "internal bug detected" message instead of crashing the node.
The essence of this work comes from several comments:
1. https://github.com/bitcoin/bitcoin/pull/26560#discussion_r1037395665
2. https://github.com/bitcoin/bitcoin/pull/25729#discussion_r940619491
3. https://github.com/bitcoin/bitcoin/pull/25269#pullrequestreview-1135240825
4. https://github.com/bitcoin/bitcoin/issues/23144 (which is connected to #24845)
ACKs for top commit:
ishaanam:
crACK 76dc547ee7
achow101:
ACK 76dc547ee7
aureleoules:
ACK 76dc547ee7
theStack:
ACK 76dc547ee7🌇
Tree-SHA512: 9de30792d7a5849cae77747aa978e70390b66ee9d082779a56088a024f82e725b0af050e6603aece0ac8229f6d73bc471ba97b4ab69dc7eddf419f5f56ae89a5
Aside from the cleanup, this solves a bug in the following-up commit. Because, in these
tests, we are manually adding/erasing outputs from the CoinsResult object but never
updating the internal total amount field.
so if there is an error in any of the pre-set coins, we can fail right away
without computing the wallet available coins set (calling `AvailableCoins`)
which is a slow operation as it goes through the entire wallet's txes map.
----------------------
And to make the Coin Selection flow cleared, have decoupled SelectCoins in two functions:
1) AutomaticCoinSelection.
2) SelectCoins.
1) AutomaticCoinSelection:
Receives a set of coins and selects the best subset of them to
cover the target amount.
2) SelectCoins
In charge of select all the user manually selected coins first ("pre-set inputs"), and
if coin_control 'm_allow_other_inputs=true', call 'AutomaticCoinSelection' to select a
subset of coins owned by the wallet to cover for the target - preset_inputs.total_amount
remaining value.
