category

# `glicko2_common`

Shared internal Glicko-2 numeric helpers for rating updates, volatility search, and scale conversions.

Availability:
`logtalk_load(ranking_protocols(loader))`
Author: Paulo Moura
Version: 1:0:0
Date: 2026-05-02
Compilation flags:
`static`
Uses:
avltree
Remarks:
(none)
Inherited public predicates:
(none)

## Public predicates

(no local declarations; see entity ancestors if any)

## Protected predicates

### `update_item_parameters/10`

Computes the simultaneous Glicko-2 rating, deviation, and volatility update for one item over a rating period using the current dictionaries and aggregated game results.

Compilation flags:
`static`
Template:
`update_item_parameters(Item,ItemResults,Ratings,Deviations,Volatilities,Tau,VolatilityTolerance,UpdatedRating,UpdatedDeviation,UpdatedVolatility)`
Mode and number of proofs:
`update_item_parameters(+term,+list(compound),+compound,+compound,+compound,+number,+number,-number,-number,-number)` - `one`

### `to_mu/2`

Converts a rating on the external Glicko scale to the internal `mu` scale.

Compilation flags:
`static`
Template:
`to_mu(Rating,Mu)`
Mode and number of proofs:
`to_mu(+number,-number)` - `one`

### `to_phi/2`

Converts a rating deviation on the external Glicko scale to the internal `phi` scale.

Compilation flags:
`static`
Template:
`to_phi(Deviation,Phi)`
Mode and number of proofs:
`to_phi(+number,-number)` - `one`

### `to_rating/2`

Converts a value on the internal `mu` scale back to the external Glicko rating scale.

Compilation flags:
`static`
Template:
`to_rating(Mu,Rating)`
Mode and number of proofs:
`to_rating(+number,-number)` - `one`

### `to_deviation/2`

Converts a value on the internal `phi` scale back to the external Glicko rating-deviation scale.

Compilation flags:
`static`
Template:
`to_deviation(Phi,Deviation)`
Mode and number of proofs:
`to_deviation(+number,-number)` - `one`

## Private predicates

(no local declarations; see entity ancestors if any)

## Operators

(none)