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ashvale-station/ashvale/models/nowcast.py
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# Copyright 2026 Kemal Yaylali
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""Multi-horizon forecasting: one direct head per (target, horizon).
Direct rather than recursive. A recursive one-step model iterated 288
times to reach 24 hours compounds its own bias into a beautifully smooth
lie. Direct heads cost more memory (six horizons x three targets = 18
small models, about 150 kB total) and are worth every byte.
Each head predicts a *delta from now*, then the ensemble blends three
opinions with weights that are themselves learned online:
persistence : it will be exactly as it is now
climatology : it will be whatever this hour of this day usually is
learned RLS : it will be now plus what the regressors imply
Persistence wins at 15 minutes. Climatology wins at 24 hours. The RLS
head wins in the middle, which is exactly the region a physical
forecaster finds hardest. The blend weights are updated by exponentiated
gradient (Hedge), so the ensemble is never worse than its best member by
more than a log factor, and it re-weights itself within a day when the
season turns.
"""
from __future__ import annotations
from typing import Dict, List, Optional, Tuple
import numpy as np
from ..features import N_FEATURES, Standardiser, supervised_pairs
from .rls import AdaptiveConformal, RecursiveLeastSquares
MEMBERS = ("persistence", "climatology", "learned")
class ForecastHead:
"""One target, one horizon."""
def __init__(self, target: str, horizon_s: int, n_features: int = N_FEATURES,
forgetting: float = 0.9985, delta: float = 100.0,
alpha: float = 0.10, conformal_window: int = 400,
gamma: float = 0.01, hedge_eta: float = 0.35):
self.target = target
self.horizon_s = int(horizon_s)
self.model = RecursiveLeastSquares(n_features, forgetting, delta)
self.conformal = AdaptiveConformal(alpha, conformal_window, gamma)
self.weights = np.ones(len(MEMBERS)) / len(MEMBERS)
self.eta = float(hedge_eta)
self.member_mae = np.zeros(len(MEMBERS))
self.n_scored = 0
# -------------------------------------------------------- prediction
def predict(self, x: np.ndarray, anchor: float,
climatology_delta: float = 0.0) -> Dict[str, float]:
learned_delta = self.model.predict(x)
deltas = np.array([0.0, float(climatology_delta), float(learned_delta)])
blended = float(np.dot(self.weights, deltas))
mu = float(anchor + blended)
sigma = self.model.predict_std(x, self.model.noise_var)
lo, hi = self.conformal.interval(mu, fallback_sigma=sigma)
return {
"mu": mu,
"lo": lo,
"hi": hi,
"sigma": sigma,
"delta": blended,
"members": {m: float(anchor + d) for m, d in zip(MEMBERS, deltas)},
"weights": {m: float(w) for m, w in zip(MEMBERS, self.weights)},
}
# ---------------------------------------------------------- learning
def learn(self, x: np.ndarray, anchor: float, truth: float,
climatology_delta: float = 0.0) -> float:
"""One supervised step given a matured target."""
deltas = np.array([0.0, float(climatology_delta),
float(self.model.predict(x))])
member_pred = anchor + deltas
losses = np.abs(member_pred - truth)
# Hedge / exponentiated gradient on normalised losses
scale = max(float(np.max(losses)), 1e-6)
self.weights *= np.exp(-self.eta * losses / scale)
self.weights = np.clip(self.weights, 1e-4, None)
self.weights /= self.weights.sum()
blended = float(np.dot(self.weights, member_pred))
residual = truth - blended
self.conformal.observe(residual)
self.model.update(x, truth - anchor)
self.member_mae = 0.98 * self.member_mae + 0.02 * losses
self.n_scored += 1
return residual
def to_dict(self) -> Dict:
return {"target": self.target, "horizon_s": self.horizon_s,
"model": self.model.to_dict(), "conformal": self.conformal.to_dict(),
"weights": self.weights.tolist(), "eta": self.eta,
"member_mae": self.member_mae.tolist(), "n_scored": self.n_scored}
@classmethod
def from_dict(cls, s: Dict) -> "ForecastHead":
h = cls(s["target"], s["horizon_s"])
h.model = RecursiveLeastSquares.from_dict(s["model"])
h.conformal = AdaptiveConformal.from_dict(s["conformal"])
h.weights = np.array(s["weights"], dtype=float)
h.eta = s["eta"]
h.member_mae = np.array(s["member_mae"], dtype=float)
h.n_scored = s.get("n_scored", 0)
return h
class NowcastEnsemble:
"""The full bank of heads plus the shared feature standardiser."""
def __init__(self, targets: Tuple[str, ...], horizons_s: Tuple[int, ...],
cfg_model):
self.targets = tuple(targets)
self.horizons = tuple(int(h) for h in horizons_s)
self.grid_s = int(cfg_model.grid_s)
self.scaler = Standardiser(N_FEATURES)
self.heads: Dict[Tuple[str, int], ForecastHead] = {
(t, h): ForecastHead(
t, h, N_FEATURES, cfg_model.rls_forgetting, cfg_model.rls_delta,
cfg_model.conformal_alpha, cfg_model.conformal_window,
cfg_model.conformal_gamma,
)
for t in self.targets for h in self.horizons
}
self.trained_rows = 0
# ------------------------------------------------------------ train
def fit(self, X: np.ndarray, valid: np.ndarray, series: Dict[str, np.ndarray],
climatology=None, grid_ts: Optional[np.ndarray] = None,
passes: int = 1, max_pairs: int = 2500) -> Dict[str, int]:
"""Batch-update every head from history.
`max_pairs` bounds the work per head to the most recent samples.
This is not a shortcut: with a forgetting factor of 0.9985 the
effective memory is about 11 hours, so the 4000th-most-recent
sample carries a weight of roughly e^-6. Training on it costs
real seconds on a Cortex-A53 and buys nothing measurable.
"""
"""Batch pass over history. Called on startup and every retrain tick."""
if X.shape[0] < 10:
return {"rows": 0}
self.scaler.partial_fit(X[valid][:: max(1, X.shape[0] // 2000)])
Xs = self.scaler.transform(X)
counts = {}
for target in self.targets:
y = series[target]
for h in self.horizons:
steps = max(int(round(h / self.grid_s)), 1)
Xa, dy, anchor = supervised_pairs(Xs, valid, y, steps)
if Xa.shape[0] < 5:
counts[f"{target}@{h}"] = 0
continue
if Xa.shape[0] > max_pairs:
Xa, dy, anchor = Xa[-max_pairs:], dy[-max_pairs:], anchor[-max_pairs:]
head = self.heads[(target, h)]
clim = np.zeros(Xa.shape[0])
if climatology is not None and grid_ts is not None and climatology.ready:
n = grid_ts.size
ts_a = grid_ts[:n - steps]
mask_len = min(ts_a.size, Xa.shape[0])
clim_now = climatology.predict(target, ts_a[-mask_len:])
clim_fut = climatology.predict(target, ts_a[-mask_len:] + h)
clim = np.zeros(Xa.shape[0])
clim[-mask_len:] = clim_fut - clim_now
for _ in range(max(int(passes), 1)):
for i in range(Xa.shape[0]):
head.learn(Xa[i], anchor[i], anchor[i] + dy[i], clim[i])
counts[f"{target}@{h}"] = int(Xa.shape[0])
self.trained_rows = int(X.shape[0])
return counts
# --------------------------------------------------------- inference
def forecast(self, x_raw: np.ndarray, anchors: Dict[str, float], now: float,
climatology=None) -> Dict[str, Dict[int, Dict[str, float]]]:
x = self.scaler.transform(np.atleast_2d(x_raw))[0]
out: Dict[str, Dict[int, Dict[str, float]]] = {}
for target in self.targets:
anchor = float(anchors.get(target, 0.0))
out[target] = {}
for h in self.horizons:
clim_delta = 0.0
if climatology is not None and climatology.ready:
clim_delta = float(climatology.predict(target, np.array([now + h]))[0]
- climatology.predict(target, np.array([now]))[0])
out[target][h] = self.heads[(target, h)].predict(x, anchor, clim_delta)
return out
def diagnostics(self) -> List[Dict]:
rows = []
for (target, h), head in sorted(self.heads.items()):
rows.append({
"target": target,
"horizon_s": h,
"n_updates": head.model.n_updates,
"n_scored": head.n_scored,
"weights": {m: round(float(w), 3) for m, w in zip(MEMBERS, head.weights)},
"member_mae": {m: round(float(v), 3) for m, v in zip(MEMBERS, head.member_mae)},
"conformal_alpha": round(head.conformal.alpha, 4),
"conformal_halfwidth": round(float(head.conformal.quantile()), 3)
if np.isfinite(head.conformal.quantile()) else None,
"coverage": round(head.conformal.empirical_coverage, 3)
if np.isfinite(head.conformal.empirical_coverage) else None,
})
return rows
def to_dict(self) -> Dict:
return {
"targets": list(self.targets),
"horizons": list(self.horizons),
"grid_s": self.grid_s,
"scaler": self.scaler.to_dict(),
"heads": [h.to_dict() for h in self.heads.values()],
"trained_rows": self.trained_rows,
}
def load_dict(self, s: Dict) -> None:
self.scaler = Standardiser.from_dict(s["scaler"])
for hs in s["heads"]:
head = ForecastHead.from_dict(hs)
self.heads[(head.target, head.horizon_s)] = head
self.trained_rows = s.get("trained_rows", 0)