mirror of https://github.com/status-im/EIPs.git
63 lines
2.9 KiB
Markdown
63 lines
2.9 KiB
Markdown
---
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eip: 1108
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title: Reduce alt_bn128 precompile gas costs
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author: Antonio Salazar Cardozo (@shadowfiend)
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status: Draft
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type: Standards Track
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category: Core
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created: 2018-05-21
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requires: 196, 197
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---
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## Short Description
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Recent changes to the underlying library used by the official Go reference
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implementation led to significant performance gains for the `ECADD`, `ECMUL`,
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and pairing check precompiled contracts on the `alt_bn128` elliptic curve.
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What is more, the performance boost for those operations can be also observed
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for Parity client.
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Faster operations on Ethereum clients should be reflected in reduced gas costs.
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## Motivation
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Recently, the underlying library used by the [official Go reference
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implementation](https://github.com/ethereum/go-ethereum) to implement the
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`ECADD` (at address `0x06`), `ECMUL` (at address `0x07`), and pairing check (at
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address `0x08`) precompiled contracts was shifted to [Cloudflare's bn256
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library](https://github.com/cloudflare/bn256). Based on the [initial PR that
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introduced this change](https://github.com/ethereum/go-ethereum/pull/16203),
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and corroborated in [a later
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note](https://github.com/ethereum/go-ethereum/pull/16301#issuecomment-372687543),
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the computational cost of `ECADD`, `ECMUL`, and pairing checks (excepting the
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constant) has dropped roughly an order of magnitude across the board.
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Also, [optimisations in the bn library](https://github.com/paritytech/bn/pull/9)
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used by the [Parity client](https://github.com/paritytech/parity-ethereum) led to a
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significant performance boost we
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[benchmarked](https://gist.github.com/pdyraga/4649b74436940a01e8221d85e80bfeef)
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and compared against the [previous
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results](https://github.com/ethereum/benchmarking/blob/master/constantinople/analysis2.md).
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## Specification
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Following is a table with the current gas cost and new gas cost:
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| Contract | Address | Current Gas Cost | Updated Gas Cost |
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| ------------- | --------- | ----------------------------- | ------------------- |
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| `ECADD` | `0x06` | 500<sup>[1]</sup> | 150 |
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| `ECMUL` | `0x07` | 40 000<sup>[1]</sup> | 6 000 |
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| Pairing check | `0x08` | 80 000 * k + 100 000<sup>[2]</sup>| 28 300 * k + 35 450 |
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The gas costs for `ECADD` and `ECMUL` are updates to the costs listed in
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EIP-196, while the gas costs for the pairing check are updates to the cost
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listed in EIP-197. Updated gas costs have been adjusted to the less performant
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client which is Parity, according to benchmarks<sup>[3]</sup>.
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[1]- Per [EIP-196](https://github.com/ethereum/EIPs/blob/984cf5de90bbf5fbe7e49be227b0c2f9567e661e/EIPS/eip-196.md#gas-costs).
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[2]- Per [EIP-197](https://github.com/ethereum/EIPs/blob/df132cd37efb3986f9cd3ef4922b15a767d2c54a/EIPS/eip-197.md#specification).
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[3]- [Parity benchmarks.](https://gist.github.com/pdyraga/4649b74436940a01e8221d85e80bfeef)
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