# Epoch

## Overview

An epoch is a fixed period of blocks in the MAP Relay Chain during which the validator set remains constant. At the end of each epoch, a new validator set is elected for the next epoch.

## Epoch Parameters

| Parameter      | Value         | Description                |
| -------------- | ------------- | -------------------------- |
| Epoch Size     | 50,000 blocks | Number of blocks per epoch |
| Block Time     | \~5 seconds   | Time between blocks        |
| Epoch Duration | \~3 days      | Approximate time per epoch |

## Epoch Lifecycle

### 1. Epoch Start

At the beginning of each epoch:

* The new validator set becomes active
* Validators begin producing blocks in round-robin fashion
* All pending votes from the previous epoch are processed

### 2. During Epoch

Throughout the epoch:

* The validator set remains fixed
* Validators take turns proposing blocks
* Transactions and smart contracts are executed
* Votes for the next epoch's validators can be cast

### 3. Epoch End

At the last block of each epoch:

* Epoch rewards are calculated and distributed
* The election contract is called to select the next validator set
* Validator voting state is reset (pending votes cleared)

## Validator Elections

During the generation of the last block in each epoch, the election contract selects the validator set for the next epoch:

1. **Vote Tallying**: The contract maintains a sorted list of each validator's locked MAPO votes (pending or activated)
2. **Selection**: Validators are selected based on the proportion of votes received
3. **Constraints**:
   * Minimum validators: 1
   * Maximum validators: 100
   * If minimum is not met, no changes are made to the validator set

## Epoch Rewards

At the end of each epoch, rewards are distributed to:

* **Validators**: For participating in block production and consensus
* **Voters**: For locking MAPO and voting for validators

The reward distribution is proportional to:

* Validator's participation in block production
* Amount of MAPO locked and voted

## Voting and Epochs

### Vote States

* **Pending Votes**: Votes cast during the current epoch, not yet activated
* **Active Votes**: Votes that have been activated and are earning rewards

### Vote Activation

* Pending votes are automatically activated at the end of the epoch when the validator is elected
* Voters can also manually activate their pending votes after the epoch in which they voted

### Vote Reset

Every epoch transaction resets the validator voting state:

* Any pending votes for adding/removing validators are reset
* This ensures a clean slate for each epoch's governance decisions

## Related Topics

* [Proof of Stake](/dev-docs/relay-chain/consensus/pos.md)
* [Istanbul BFT](/dev-docs/relay-chain/consensus/istanbul-bft.md)
* [Election](/dev-docs/relay-chain/consensus/election.md)
* [Rewards](/dev-docs/relay-chain/consensus/rewards.md)


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