Skip to content

perf: use saturating arithmetic in balance updates for SIMD vectorization #282

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
lodekeeper-z wants to merge 2 commits into
base: main
Choose a base branch
from
Open

perf: use saturating arithmetic in balance updates for SIMD vectorization #282

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
ec89bf6
perf: use saturating arithmetic in balance updates for SIMD vectoriza…
lodekeeper-z Mar 27, 2026
29d60ec
address gemini review: debug asserts + prose comment
lodekeeper-z Mar 27, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
1 change: 1 addition & 0 deletions .gitignore
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -20,3 +20,4 @@ node_modules/
# Claude Code local config
.claude/settings.local.json
.claude/plans/
zig-pkg/
10 changes: 8 additions & 2 deletions src/state_transition/epoch/process_rewards_and_penalties.zig
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -31,14 +31,20 @@ pub fn processRewardsAndPenalties(
const balances = try state.balancesSlice(allocator);
defer allocator.free(balances);

// Use saturating arithmetic for performance. Saturating operations are branchless, which
// enables SIMD auto-vectorization of the balance update loop. This is safe because a
// balance overflow is mathematically impossible: the maximum total ETH supply (~1.2e17 Gwei)
// is more than 150x smaller than the max u64 value (~1.8e19 Gwei).
if (slashing_penalties) |slashings| {
for (rewards, penalties, balances, 0..) |reward, penalty, *balance, i| {
const slashing: u64 = if (i < slashings.len) slashings[i] else 0;
balance.* = (try std.math.add(u64, balance.*, reward)) -| penalty -| slashing;
std.debug.assert(balance.* <= std.math.maxInt(u64) - reward);
balance.* = ((balance.* +| reward) -| penalty) -| slashing;
Copy link
Copy Markdown
Contributor

@gemini-code-assist gemini-code-assist Bot Mar 27, 2026

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

medium

To uphold the style guide's emphasis on safety (Safety, performance, and developer experience. In that order., line 5), it's best to add a std.debug.assert here. This will verify the no-overflow assumption during testing without impacting performance in ReleaseFast builds. This also serves as executable documentation for the invariant you've identified.

From the style guide:

Assert all function arguments and return values, pre/postconditions and invariants. (line 51)

I've also removed a redundant set of parentheses for cleaner code.

            std.debug.assert(balance.* <= std.math.maxInt(u64) - reward);
            balance.* = (balance.* +| reward) -| penalty -| slashing;
References
  1. The style guide prioritizes safety over performance and mandates asserting all pre/postconditions and invariants. Adding a debug assertion maintains safety during testing without compromising release performance. (link)

}
} else {
for (rewards, penalties, balances) |reward, penalty, *balance| {
balance.* = (try std.math.add(u64, balance.*, reward)) -| penalty;
std.debug.assert(balance.* <= std.math.maxInt(u64) - reward);
balance.* = (balance.* +| reward) -| penalty;
Copy link
Copy Markdown
Contributor

@gemini-code-assist gemini-code-assist Bot Mar 27, 2026

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

medium

Similarly, please add a std.debug.assert here to ensure safety during testing, in line with the style guide's emphasis on assertions.

            std.debug.assert(balance.* <= std.math.maxInt(u64) - reward);
            balance.* = (balance.* +| reward) -| penalty;
References
  1. The style guide prioritizes safety over performance and mandates asserting all pre/postconditions and invariants. Adding a debug assertion maintains safety during testing without compromising release performance. (link)

}
}

Expand Down
Loading