Implement binary search based fee estimation algorithm

[kkovaacs]

Starknet 0.13.4 introduces runtime L2 gas accounting. A dedicated withdraw_gas libfunc call is added by the compiler into loops. For non-tail-recursive calls withdraw_gas always requires the worst-case gas amount to be available, so the compiler inserts redeposit_gas libfunc calls onto paths that cost less than the worst-case. (For a detailed analysis please check this document.)

This means that simply taking the L2 gas costs of a transaction execution and using that as a fee cap when submitting a transaction might lead to the transaction reverting due to insufficient gas. Whether or not this happens depends on whether there are paths during the execution where worst-case gas requirements are significantly larger than the actual costs.

To get a fee estimate that guarantees that the transaction will succeed we have to resort to trial-and-error:

• Run transaction with a large fee cap (maybe balance induced but can be max as well), get consumed gas g.
• Unfortunately the VM doesn't currently do accounting on gas refunds (g'), so let's just assume that in most cases the transaction does not have a pathological case and try executing it with (1 + epsilon) * g gas.
  • If that succeeds, just use that as a fee estimate.
  • If the transaction reverts, check that the cause of the revert is insufficient gas and do a binary search for a sufficient gas cap within [ (1 + epsilon) * g, max ].