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EIP-1108 updated with the new gas costs #1452

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Sep 26, 2018
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EIP-1108 updated with the new gas costs #1452

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6fa1a84
Updated EIP-1108 with the new gas costs
pdyraga Sep 26, 2018
fc623ce
Minor language fixes
pdyraga Sep 26, 2018
3611087
Updated notation for pairing check gas cost
pdyraga Sep 26, 2018
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26 changes: 20 additions & 6 deletions EIPS/eip-1108.md
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Expand Up @@ -13,8 +13,12 @@ requires: 196, 197

Recent changes to the underlying library used by the official Go reference
implementation led to significant performance gains for the `ECADD`, `ECMUL`,
and pairing check precompiled contracts on the `alt_bn128` elliptic curve, which
should be reflected in reduced gas costs.
and pairing check precompiled contracts on the `alt_bn128` elliptic curve.

What is more, the performance boost for those operations can be also observed
for Parity client.

Faster operations on Ethereum clients should be reflected in reduced gas costs.

## Motivation

Expand All @@ -29,20 +33,30 @@ note](https://github.com/ethereum/go-ethereum/pull/16301#issuecomment-372687543)
the computational cost of `ECADD`, `ECMUL`, and pairing checks (excepting the
constant) has dropped roughly an order of magnitude across the board.

Also, [optimisations in the bn library](https://github.com/paritytech/bn/pull/9)
used by the [Parity client](https://github.com/paritytech/parity-ethereum) led to a
significant performance boost we
[benchmarked](https://gist.github.com/pdyraga/4649b74436940a01e8221d85e80bfeef)
and compared against the [previous
results](https://github.com/ethereum/benchmarking/blob/master/constantinople/analysis2.md).

## Specification

Following is a table with the current gas cost and new gas cost:

| Contract | Address | Current Gas Cost | Updated Gas Cost |
| ------------- | --------- | ----------------------------- | ------------------- |
| `ECADD` | `0x06` | 500<sup>[1]</sup> | 50 |
| `ECMUL` | `0x07` | 40 000<sup>[1]</sup> | 2 000 |
| Pairing check | `0x08` | 80 000k + 100 000<sup>[2]</sup>| 5 500k + 80 000 |
| `ECADD` | `0x06` | 500<sup>[1]</sup> | 150 |
| `ECMUL` | `0x07` | 40 000<sup>[1]</sup> | 6 000 |
| Pairing check | `0x08` | 80 000 * k + 100 000<sup>[2]</sup>| 28 300 * k + 35 450 |

The gas costs for `ECADD` and `ECMUL` are updates to the costs listed in
EIP-196, while the gas costs for the pairing check are updates to the cost
listed in EIP-197.
listed in EIP-197. Updated gas costs have been adjusted to the less performant
client which is Parity, according to benchmarks<sup>[3]</sup>.

[1]- Per [EIP-196](https://github.com/ethereum/EIPs/blob/984cf5de90bbf5fbe7e49be227b0c2f9567e661e/EIPS/eip-196.md#gas-costs).

[2]- Per [EIP-197](https://github.com/ethereum/EIPs/blob/df132cd37efb3986f9cd3ef4922b15a767d2c54a/EIPS/eip-197.md#specification).

[3]- [Parity benchmarks.](https://gist.github.com/pdyraga/4649b74436940a01e8221d85e80bfeef)