DifficultySet

Event Re-added v101 → v219, v233 → v265, v273 → v277, v290 → current #11

Emitted when POW registration difficulty is changed.

Useful for: minersvalidatorssubnet ownersanalyticsdevelopers

The Big Picture

Proof-of-work registration lets you join a subnet by solving a computational puzzle instead of burning TAO. The difficulty controls how hard this puzzle is - higher difficulty means more computation (time/electricity) to find a valid solution. Difficulty normally adjusts automatically based on registration rate, but this event fires when it's manually set. Subnet owners might adjust difficulty to control registration pace or in response to unusual conditions.

Why This Matters

POW registration is the 'free' way to join a subnet - you pay with computation instead of TAO. Difficulty determines how much computation you need. A difficulty drop means easier registration (less GPU time). A difficulty spike means harder registration (more GPU time or switching to burn).

Example Scenario

You're mining POW to register on subnet 8. Currently difficulty is 1,000,000 and your GPU finds solutions in about 10 minutes. The subnet owner sets difficulty to 2,000,000. DifficultySet fires. Now your GPU needs about 20 minutes per solution. You might decide to burn TAO instead if time is critical.

Common Questions

Why would difficulty be manually set instead of auto-adjusting?: Usually difficulty auto-adjusts based on registration rate. Manual setting happens when the subnet owner wants to override this - perhaps to quickly open registration (lower difficulty) or slow it down (higher difficulty) for some strategic reason.
What's the relationship between difficulty and GPU time?: Roughly linear. Double the difficulty = double the expected time to find a solution. But it's probabilistic - you might get lucky quickly or take much longer.
Should I use POW or burn registration?: POW costs electricity/time, burn costs TAO directly. Compare your electricity costs and time value against the current burn rate. If you have spare GPU capacity, POW can be cheaper. If time is critical or difficulty is very high, burn might be better.

Use Cases

Monitor registration difficulty to time your registration
Track difficulty trends to predict future costs
Alert when difficulty spikes or drops significantly
Analyze subnet competitiveness based on difficulty

How to Use This Event

→ Track difficulty on subnets you want to join via POW
→ Monitor for sudden difficulty changes that affect registration strategy
→ Build difficulty history charts for subnets

From Chain Metadata

the difficulty has been set for a subnet.

Triggers

Preconditions

Caller has admin/sudo privileges
New difficulty within MinDifficulty and MaxDifficulty bounds

Effects

Postconditions

Difficulty updated for subnet
POW registrations must meet new difficulty target

Side Effects

Affects POW registration computational cost
May make registration easier or harder immediately

Event Data

#	Name	Type	Description
0	arg0	u16	Event field #0 (u16)
1	arg1	u64	Event field #1 (u64)

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 });

// Subscribe to DifficultySet events
api.query.system.events((events) => {
  events
    .filter(({ event }) =>
      event.section === stringCamelCase("SubtensorModule") &&
      event.method === "DifficultySet"
    )
    .forEach(({ event }) => {
      console.log("DifficultySet:", event.data.toHuman());
    });
});

On-Chain Activity

Emission Frequency

●●●●○○ Significant 1M–5M emissions

Major features with millions of emissions

#26 most emitted event

As of block 7,429,232

Version History

Version:

v101 block 1 2 args

v233 block 4,920,350 2 args

v273 block 5,659,032 2 args

v290 block 5,947,548 2 args Current

Runtime Info

View Source

Pallet Index: 7
Event Index: 11
First Version: v101
Current Version: v393

Back to SubtensorModule Events