Shortcut for 2^e #233
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Shortcut for 2^e #233
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axic
reviewed
Jun 3, 2020
| auto exp_bytes = as_bytes(exponent); | ||
| uint8_t bit_to_set = exp_bytes[0]; | ||
| exp_bytes[0] = 0; | ||
| exp_bytes[bit_to_set >> 3] = uint8_t(uint8_t(1) << (bit_to_set & 7)); |
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Why not something like exponent = 2 << exponent; ?
@chfast would either of these solutions have a significant speed difference?
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Looks like at least in my benchmarks the 1 << exponent is the fastest (surprisingly). Full story in chfast/intx#146.
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Yes, this makes sense, but I think I will move to the implementation of |
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There are a lot of contracts on the Ethereum mainnet that were compiled with Solidity prior to the shifting operations were available. For those, exponentiation 2^160 is used to emulate 1<<160. Measurements performed on turbo-geth confirm this. Since we are planning to integrate evmone into turbo-geth, and we have already implemented this shortcut (erigontech/erigon#505), it would be good to maintain that in evmone.
For #231