perf(validatePayment): loop over proving periods instead of epochs

[wjmelements]

When we settle a Payment segment, FilecoinWarmStorageService.validatePayment loops over epochs like this:

        // Check each epoch in the range
        for (uint256 epoch = fromEpoch + 1; epoch <= toEpoch; epoch++) {
            bool isProven = isEpochProven(dataSetId, epoch);

            if (isProven) {
                provenEpochCount++;
                lastProvenEpoch = epoch;
            }
        }

isEpochProven ultimately does

        // Get the period this epoch belongs to
        uint256 periodId = getProvingPeriodForEpoch(dataSetId, epoch);

        // Special case: current ongoing proving period
        uint256 currentPeriod = getProvingPeriodForEpoch(dataSetId, block.number);
        if (periodId == currentPeriod) {
            // For the current period, check if it has been proven already
            return provenThisPeriod[dataSetId];
        }

        // For past periods, check the provenPeriods mapping
        return provenPeriods[dataSetId][periodId];

getProvingPeriodForEpoch calculates periodId this way:

        return (epoch - activationEpoch) / maxProvingPeriod;

So the top level loop can be optimized by looping over proving periods instead of over epochs. The first and last epochs might need special handling, but for the other proving periods, can count like provenEpochCount += maxProvingPeriod.

[wjmelements]

provenPeriods can also be optimized to be a uint256 bitmap instead of a singular bool:

    return provenPeriods[dataSetId][periodId >> 8] & (1 << (periodId & 255));

This would reduce the storage slot access of provenPeriods by a factor 256 when looping iteratively.

[wjmelements]

Can probably remove provenThisPeriod, deriving the info from provenPeriods instead.

[parzival1821]

Hey @wjmelements can I work on this? I wanna start contributing and this looks like a good starting point

[rjan90]

Hey @dev-n-dough! Yes, feel free to start working on this. I will assign the ticket to you.

Let us know if you have any questions or need some guidance