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Merge pull request #475 from zama-ai/docsGasDec
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docs: remove decrypt from gas page
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jatZama authored Aug 22, 2024
2 parents bbf4e73 + 0c8f146 commit 051a774
Showing 1 changed file with 4 additions and 41 deletions.
45 changes: 4 additions & 41 deletions docs/guides/gas.md
Original file line number Diff line number Diff line change
Expand Up @@ -4,11 +4,10 @@ FHE operations are typically more computationally expensive than classical opera

## ebool

| Function name | Gas |
| ---------------- | ------- |
| `and`/`or`/`xor` | 26,000 |
| `not` | 30,000 |
| `decrypt` | 500,000 |
| Function name | Gas |
| ---------------- | ------ |
| `and`/`or`/`xor` | 26,000 |
| `not` | 30,000 |

## euint4

Expand All @@ -32,7 +31,6 @@ FHE operations are typically more computationally expensive than classical opera
| `neg` | 60,000 |
| `not` | 33,000 |
| `select` | 45,000 |
| `decrypt` | 500,000 |

## euint8

Expand All @@ -56,7 +54,6 @@ FHE operations are typically more computationally expensive than classical opera
| `neg` | 95,000 |
| `not` | 34,000 |
| `select` | 47,000 |
| `decrypt` | 500,000 |
| `randEuint8()` | 100,000 |

## euint16
Expand All @@ -81,7 +78,6 @@ FHE operations are typically more computationally expensive than classical opera
| `neg` | 131,000 |
| `not` | 35,000 |
| `select` | 47,000 |
| `decrypt` | 500,000 |
| `randEuint16()` | 100,000 |

## euint32
Expand All @@ -106,7 +102,6 @@ FHE operations are typically more computationally expensive than classical opera
| `neg` | 160,000 |
| `not` | 36,000 |
| `select` | 50,000 |
| `decrypt` | 500,000 |
| `randEuint32()` | 100,000 |

## euint64
Expand All @@ -131,7 +126,6 @@ FHE operations are typically more computationally expensive than classical opera
| `neg` | 199,000 |
| `not` | 37,000 |
| `select` | 53,000 |
| `decrypt` | 500,000 |
| `randEuint64()` | 100,000 |

## eaddress
Expand All @@ -140,37 +134,6 @@ FHE operations are typically more computationally expensive than classical opera
| ------------- | ------- |
| `eq`/`ne` | 90,000 |

## Estimate gas

When you call estimate gas method, we can’t determine accurately the gas usage if your function uses `TFHE.decrypt`. During gas estimation, all `TFHE.decrypt()` will return `1`.

### What does it mean?

- `require(TFHE.decrypt(ebool));` will be ok but `require(!TFHE.decrypt(ebool));` will fail during estimation (revert transaction)
- A loop, where you expect a decrypt to be false to break, will never end in gas estimate method (and fails), since the decrypt will always return `1` (true)
- On the other hand, if your loop should last 2 or 3 cycles, until the value is 1, the estimation will be below.
- If you have branches (if/else) based on a decryption, the estimation will use the branch running when the decryption is `1`

While it’s challenging to accurately estimate gas consumption when using `TFHE.decrypt`, we strongly encourage you to take this into consideration.

### What can I do?

A possible solution is to overestimate your gas estimation. You can take this function (with ethers.js) as an example where we multiply the gas limit by `1.2`.

```typescript
export const createTransaction = async <A extends [...{ [I in keyof A]-?: A[I] | Typed }]>(
method: TypedContractMethod<A>,
...params: A
) => {
const gasLimit = await method.estimateGas(...params);
const updatedParams: ContractMethodArgs<A> = [
...params,
{ gasLimit: Math.min(Math.round(+gasLimit.toString() * 1.2), 10000000) },
];
return method(...updatedParams);
};
```

## Gas limit

The current devnet has a gas limit of **10,000,000**. If you send a transaction exceeding this limit, it won't be executed. Consequently, your wallet won't be able to emit a new transaction. To address this, emit a new transaction with the same nonce but the correct gas limit.
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