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Optimize ResourceConstraintManager v2 code #421

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Optimize ResourceConstraintManager v2 code #421

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64 changes: 29 additions & 35 deletions src/chain/ResourceConstraintManager.sol
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Original file line number Diff line number Diff line change
Expand Up @@ -132,6 +132,9 @@ contract ResourceConstraintManager is AccessControlEnumerable {
) {
revert InvalidPeriod(targetPerSec, adjustmentWindowSecs, startingBacklogValue);
}

uint256 nResources = constraints[i].resources.length;
uint64 maxWeight = 0;
{
// Check for unsorted or duplicate resource kinds within this constraint
// The check is performed here instead of in the loop below (for calculating pricing exponents)
Expand All @@ -140,7 +143,6 @@ contract ResourceConstraintManager is AccessControlEnumerable {
// lastResourceKind starts at 0 so that Unknown (kind=0) is rejected by the sorted check
// out-of-range enum values are automatically rejected
uint8 lastResourceKind = 0;
uint256 nResources = constraints[i].resources.length;
for (uint256 j = 0; j < nResources; ++j) {
uint8 kind = uint8(constraints[i].resources[j].resource);
// check that resource kinds are sorted and contain no duplicates
Expand All @@ -154,50 +156,42 @@ contract ResourceConstraintManager is AccessControlEnumerable {
revert InvalidResources(kind);
}
lastResourceKind = kind;
}
}
if (startingBacklogValue > 0) {
// Find the maximum weight among all resources in this constraint
uint64 maxWeight = 0;
uint256 nResources = constraints[i].resources.length;
for (uint256 j = 0; j < nResources; ++j) {

// Find the maximum weight among all resources in this constraint
uint64 weight = constraints[i].resources[j].weight;
if (weight > maxWeight) {
maxWeight = weight;
}
}

if (maxWeight > 0) {
// Neither of these values can be zero due to the earlier checks, so this division is safe
uint256 divisor =
uint256(adjustmentWindowSecs) * uint256(targetPerSec) * uint256(maxWeight);

// Calculate per-resource-kind exponent contribution
// we scale by 1000 to improve precision in calculating the exponent
// since this division will round down, it's always possible for the real exponent to be up to
// the number of constraints greater than the value we measure
// Operation is performed in uint256 to avoid overflow, but the result is guaranteed to fit in uint64 due to the earlier check
for (uint256 j = 0; j < nResources; ++j) {
uint8 kind = uint8(constraints[i].resources[j].resource);
uint64 weight = constraints[i].resources[j].weight;
pricingExponents[kind] +=
uint64(uint256(startingBacklogValue) * uint256(weight) * 1000 / divisor);
}
if ((startingBacklogValue > 0) && (maxWeight > 0)) {
// Neither of these values can be zero due to the earlier checks, so this division is safe
uint256 divisor =
uint256(adjustmentWindowSecs) * uint256(targetPerSec) * uint256(maxWeight);

// Calculate per-resource-kind exponent contribution
// we scale by 1000 to improve precision in calculating the exponent
// since this division will round down, it's always possible for the real exponent to be up to
// the number of constraints greater than the value we measure
// Operation is performed in uint256 to avoid overflow, but the result is guaranteed to fit in uint64 due to the earlier check
for (uint256 j = 0; j < nResources; ++j) {
uint8 kind = uint8(constraints[i].resources[j].resource);
uint64 weight = constraints[i].resources[j].weight;
pricingExponents[kind] +=
uint64(uint256(startingBacklogValue) * uint256(weight) * 1000 / divisor);

// this calculated pricing exponent will be used by nitro to calculate the gas price
// we check that the pricing exponent is below some reasonable number to avoid setting the gas price astronomically high
// as long as the gas price is not so high that no-one at all can send a transaction the chain will be able to function
// eg. these constraints can be changed again, or the sec council can send admin transactions
// with min base fee of 0.02, exponent of 8 (scaled by 1000) corresponds to a gas price of ~60 Gwei
if (pricingExponents[kind] > MAX_PRICING_EXPONENT) {
revert PricingExponentTooHigh(pricingExponents[kind]);
}
}
}
}

// this calculated pricing exponent will be used by nitro to calculate the gas price
// we check that the pricing exponent is below some reasonable number to avoid setting the gas price astronomically high
// as long as the gas price is not so high that no-one at all can send a transaction the chain will be able to function
// eg. these constraints can be changed again, or the sec council can send admin transactions
// with min base fee of 0.02, exponent of 8 (scaled by 1000) corresponds to a gas price of ~60 Gwei
for (uint8 k = 0; k < numResourceKinds; ++k) {
if (pricingExponents[k] > MAX_PRICING_EXPONENT) {
revert PricingExponentTooHigh(pricingExponents[k]);
}
}

ARB_OWNER.setMultiGasPricingConstraints(constraints);
}
}
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