Caps subnet size to ensure network scalability.
Current Value
256The Big Picture
Each subnet has a limited number of slots (UIDs) for miners and validators. This constant sets the initial cap when a subnet is created. Larger subnets allow more participants but increase computational overhead for validators who must evaluate everyone. Subnet owners can adjust this within bounds after creation.
Why This Matters
If you want to join a subnet, you need to know if there's room. Full subnets require you to outperform an existing participant to take their slot (via pruning).
Example
A subnet with MaxAllowedUids of 256 can have at most 256 active neurons. If all slots are full and you register, your registration replaces the lowest-performing neuron. With 4096 UIDs, there's more room but validators have more work evaluating everyone.
Common Questions
- Can subnet owners change the maximum?
- Yes, via hyperparameter updates, but there are upper limits enforced by the network.
- What happens if I'm the 257th registration on a 256-slot subnet?
- You don't get rejected - instead, the neuron with the lowest pruning score is removed to make room for you. If you have the lowest score, you get pruned.
From Chain Metadata
Initial maximum allowed network UIDs
Use Cases
- Registration limits
- Subnet capacity checks
Value History
| Version | Block | Change | Value |
|---|---|---|---|
| v101 | #1 | Added | 4096 |
| v385 | #7,782,670 | Changed | 4096 → 256 |
Code Examples
import { ApiPromise, WsProvider } from "@polkadot/api";
import { stringCamelCase } from "@polkadot/util";
const provider = new WsProvider("wss://entrypoint-finney.opentensor.ai:443");
const api = await ApiPromise.create({ provider });
// Query InitialMaxAllowedUids constant
const value = api.consts[stringCamelCase("SubtensorModule")][stringCamelCase("InitialMaxAllowedUids")];
console.log("InitialMaxAllowedUids:", value.toHuman());Type Information
- Type
- u16
- Byte Size
- 2 bytes
- Encoding
- fixed
- Raw Hex
- 0x0001
Version History
Runtime Info
- Pallet
- SubtensorModule
- First Version
- v101
- Latest Version
- v101
- Current Runtime
- v393