New sub-package for ML-based light-curve embeddings

.gitmodules

@@ -1,3 +1,6 @@
 [submodule "test-data"]
 	path = light-curve/tests/light-curve-test-data
 	url = https://github.com/light-curve/test-data.git
+[submodule "light-curve/tests/prep-models"]
+	path = light-curve/tests/prep-models
+	url = https://github.com/light-curve/prep-models.git

CHANGELOG.md

@@ -9,7 +9,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 
---
+- New `light_curve.embed` module with ONNX-backed light curve embedding models ([#692](https://github.com/light-curve/light-curve-python/pull/692)):
+  - `Astromer1` and `Astromer2` — transformer encoders pretrained on MACHO light curves (Donoso-Oliva et al. 2023/2026), returning 256-dimensional embeddings. Load directly from HuggingFace with `Astromer2.from_hf()`. Use the `output` parameter to select which named output to compute (`"mean"` (default), `"max"`, or `"sequence"`); onnxruntime prunes unused computation automatically.
+  - `NonOverlappingWindows`, `Beginning`, `End`, `RandomSubsample`, `MultipleReductions` — strategies for mapping variable-length light curves to fixed-length model inputs.
+  - `InputTensors` / `AstromerInputs` — typed dataclass containers for preprocessed tensors.
+  - `Dim` — enum of axis indices for the 4-D output array `(BAND, SUBSAMPLE, SEQUENCE, VALUE)`.
 
 ### Changed
 

light-curve/light_curve/embed/__init__.py

@@ -0,0 +1,32 @@
+from .astromer import Astromer1, Astromer2, create_onnx_session
+from .model import AstromerInputs, Dim, EmbeddingSession, SingleBandModel
+from .reduction import (
+    Beginning,
+    End,
+    InputTensors,
+    MultipleReductions,
+    NonOverlappingWindows,
+    RandomSubsample,
+    Reduction,
+    SingleSubsampleReduction,
+    reduction_from_str,
+)
+
+__all__ = [
+    "Astromer1",
+    "Astromer2",
+    "AstromerInputs",
+    "Beginning",
+    "Dim",
+    "EmbeddingSession",
+    "End",
+    "InputTensors",
+    "MultipleReductions",
+    "NonOverlappingWindows",
+    "RandomSubsample",
+    "Reduction",
+    "SingleBandModel",
+    "SingleSubsampleReduction",
+    "create_onnx_session",
+    "reduction_from_str",
+]

light-curve/light_curve/embed/astromer.py

@@ -0,0 +1,327 @@
+from __future__ import annotations
+
+from typing import Sequence
+
+import numpy as np
+from numpy.typing import ArrayLike
+
+from .model import AstromerInputs, SingleBandModel
+from .reduction import Reduction
+
+_ONNX_INSTALL_HINT = (
+    "An ONNX runtime is required to run embedding models. "
+    "Install the variant that matches your hardware:\n"
+    "  CPU / Apple Silicon:  pip install onnxruntime\n"
+    "  NVIDIA GPU (CUDA):    pip install onnxruntime-gpu\n"
+    "  Windows DirectML:     pip install onnxruntime-directml\n"
+    "See https://onnxruntime.ai for the full list of packages."
+)
+
+
+def create_onnx_session(model_path: str, **kwargs):
+    """Create an ``onnxruntime.InferenceSession``, with a helpful error if the package is missing.
+
+    Parameters
+    ----------
+    model_path : str
+        Path to the ONNX model file.
+    **kwargs
+        Forwarded verbatim to ``onnxruntime.InferenceSession``.
+
+    Returns
+    -------
+    onnxruntime.InferenceSession
+        A ready-to-use inference session.
+
+    Raises
+    ------
+    ImportError
+        If no onnxruntime variant is installed, with installation instructions.
+    """
+    try:
+        import onnxruntime as ort
+    except ImportError as exc:
+        raise ImportError(_ONNX_INSTALL_HINT) from exc
+    return ort.InferenceSession(model_path, **kwargs)
+
+
+class _AstromerModel(SingleBandModel):
+    """Internal base class for Astromer-family embedding models.
+
+    Provides shared preprocessing (per-window zero-mean normalisation) and
+    ONNX inference logic for all Astromer variants.  Concrete subclasses set
+    :attr:`_HF_REPO` and, if needed, override the default ``reduction``.
+
+    Output shape
+    ------------
+    :meth:`__call__` always returns a 4-D array
+    ``(n_bands, n_subsamples, seq_size, embed_dim)`` for consistency across
+    models and windowing strategies:
+
+    * ``n_bands`` — number of photometric bands; 1 when ``bands`` is ``None``.
+    * ``n_subsamples`` — windows produced by the time reduction (1 for
+      :class:`NonOverlappingWindows`, which averages all windows).
+    * ``seq_size`` — 1 for the ``"mean"`` and ``"max"`` outputs (aggregated
+      over the sequence); equal to the model's sequence length for ``"sequence"``.
+    * ``embed_dim`` — embedding dimension (256 for all Astromer models).
+
+    Use ``embedding.squeeze()`` to collapse unit dimensions when the full
+    4-D layout is not needed.
+    """
+
+    seq_size: int = 200
+    dtype: type = np.float32
+    _HF_REPO: str
+    _OUTPUTS: frozenset[str] = frozenset({"mean", "max", "sequence"})
+
+    def __init__(
+        self,
+        session,
+        *,
+        output: str = "mean",
+        bands: Sequence[str | int] | None = None,
+        reduction: str | list[str] | Reduction = "non-overlapping-windows",
+        time_red_kwargs: dict[str, object] | None = None,
+    ) -> None:
+        super().__init__(
+            session,
+            bands=bands,
+            reduction=reduction,
+            time_red_kwargs=time_red_kwargs,
+        )
+        if output not in self._OUTPUTS:
+            raise ValueError(f"Unknown output '{output}'. Must be one of: {', '.join(sorted(self._OUTPUTS))}")
+        self.output = output
+
+    @classmethod
+    def from_hf(
+        cls,
+        output: str = "mean",
+        *,
+        bands: Sequence[str | int] | None = None,
+        reduction: str | list[str] | Reduction = "non-overlapping-windows",
+        time_red_kwargs: dict[str, object] | None = None,
+        providers=None,
+        sess_options=None,
+    ) -> "_AstromerModel":
+        """Load a model from the HuggingFace Hub.
+
+        Downloads (and caches) the ONNX model file, creates an
+        ``onnxruntime.InferenceSession``, and returns a ready-to-use instance.
+        Only the requested output is computed at inference time — onnxruntime
+        prunes the unused computation graph automatically.
+
+        Parameters
+        ----------
+        output : str, optional
+            Named ONNX output to return.  One of:
+
+            * ``"mean"`` (default) — masked mean pooling over valid timesteps,
+              output shape ``(batch, 256)``
+            * ``"max"`` — masked max pooling over valid timesteps,
+              output shape ``(batch, 256)``
+            * ``"sequence"`` — per-timestep embeddings (no aggregation),
+              output shape ``(batch, seq_size, 256)``
+
+        bands : sequence of str or int, optional
+            Ordered band labels to embed.  ``None`` (default) treats the whole
+            light curve as one band.
+        reduction : str, list of str, or Reduction, optional
+            Windowing / subsampling strategy.  Defaults to
+            ``"non-overlapping-windows"``.
+        time_red_kwargs : dict, optional
+            Extra keyword arguments forwarded to :func:`reduction_from_str`
+            when ``reduction`` is given as a string.
+        providers : list of str, optional
+            ONNX Runtime execution providers, e.g.
+            ``["CUDAExecutionProvider", "CPUExecutionProvider"]``.
+        sess_options : onnxruntime.SessionOptions, optional
+            Advanced session configuration passed directly to
+            ``onnxruntime.InferenceSession``.
+
+        Returns
+        -------
+        instance of the calling class
+            Instance with a live ONNX inference session.
+
+        Raises
+        ------
+        ValueError
+            If ``output`` is not one of the recognised output names.
+        ImportError
+            If ``huggingface_hub`` is not installed, with instructions to
+            install it or to download the model file manually.
+        ImportError
+            If no ``onnxruntime`` variant is installed, with hardware-specific
+            installation instructions.
+        """
+        if output not in cls._OUTPUTS:
+            raise ValueError(f"Unknown output '{output}'. Must be one of: {', '.join(sorted(cls._OUTPUTS))}")
+
+        model_prefix = cls._HF_REPO.split("/")[-1]
+        filename = f"{model_prefix}.onnx"
+
+        try:
+            from huggingface_hub import hf_hub_download
+        except ImportError as exc:
+            hf_url = f"https://huggingface.co/{cls._HF_REPO}/resolve/main/{filename}"
+            raise ImportError(
+                "huggingface_hub is required to download models from HuggingFace.\n"
+                "Install it with:\n"
+                "  pip install huggingface-hub\n"
+                "Or download the model file directly:\n"
+                f"  {hf_url}\n"
+                "then load it with:\n"
+                "  import onnxruntime as ort\n"
+                f'  {cls.__name__}(session=ort.InferenceSession("/path/to/{filename}"), output="{output}")'
+            ) from exc
+
+        model_path = hf_hub_download(repo_id=cls._HF_REPO, filename=filename)
+
+        session_kwargs = {}
+        if providers is not None:
+            session_kwargs["providers"] = providers
+        if sess_options is not None:
+            session_kwargs["sess_options"] = sess_options
+
+        session = create_onnx_session(model_path, **session_kwargs)
+        return cls(
+            session=session,
+            output=output,
+            bands=bands,
+            reduction=reduction,
+            time_red_kwargs=time_red_kwargs,
+        )
+
+    def preprocess_lc(
+        self,
+        time: ArrayLike,
+        mag: ArrayLike,
+    ) -> AstromerInputs:
+        """Preprocess a light curve into Astromer model input tensors.
+
+        Each window is independently zero-mean normalised (time and magnitude)
+        using only the valid (non-padded) observations.  Normalisation is
+        computed in the original input precision before casting to ``float32``
+        to avoid precision loss for large values such as MJD timestamps.
+
+        Parameters
+        ----------
+        time : array-like, shape ``(n,)``
+            Observation times (e.g. MJD).
+        mag : array-like, shape ``(n,)``
+            Magnitudes.
+
+        Returns
+        -------
+        AstromerInputs
+            ``times`` and ``input`` are per-window zero-mean arrays of shape
+            ``(n_windows, seq_size, 1)`` in float32; ``mask`` is 1 for valid
+            observations and 0 for zero-padded positions, same shape and dtype.
+        """
+        time, mag, mask = self.reduction.preprocess_lc(time, mag, seq_size=self.seq_size)
+
+        bool_mask = mask  # (n_windows, seq_size), boolean
+        n_valid = mask.sum(axis=-1, keepdims=True)
+        time_mean = (time * mask).sum(axis=-1, keepdims=True) / n_valid
+        mag_mean = (mag * mask).sum(axis=-1, keepdims=True) / n_valid
+        time = np.where(mask, time - time_mean, time).astype(self.dtype)
+        mag = np.where(mask, mag - mag_mean, mag).astype(self.dtype)
+        mask = mask.astype(self.dtype)
+
+        idx = (..., np.newaxis)
+        return AstromerInputs(times=time[idx], input=mag[idx], mask=mask[idx], bool_mask=bool_mask)
+
+    def predict_tensors(self, tensors: AstromerInputs) -> np.ndarray:
+        """Run the ONNX model on pre-processed tensors and return reduced embeddings.
+
+        Parameters
+        ----------
+        tensors : AstromerInputs
+            As returned by :meth:`preprocess_lc`.
+
+        Returns
+        -------
+        np.ndarray, shape ``(n_subsamples, seq_size, embed_dim)``
+            Embeddings after applying the time reduction's aggregation.
+            For aggregated models (mean / max) ``seq_size`` is 1.
+        """
+        (raw_embedding,) = self.session.run(
+            [self.output],
+            {"input": tensors.input, "times": tensors.times, "mask_in": tensors.mask},
+        )
+
+        # Aggregated outputs (mean / max) have shape (n_windows, embed_dim); add SEQUENCE=1 axis
+        if raw_embedding.ndim == 2:
+            raw_embedding = np.expand_dims(raw_embedding, axis=1)
+
+        return self.reduction.reduce_embeddings(raw_embedding, tensors, output=self.output)
+
+
+class Astromer1(_AstromerModel):
+    """Astromer 1 embedding model (Donoso-Oliva et al. 2023).
+
+    Transformer encoder pretrained on MACHO R-band light curves via masked
+    magnitude prediction.  Accepts irregularly-sampled single-band photometry
+    and returns a 256-dimensional embedding (2 layers, 4 attention heads).
+
+    The ONNX model is hosted on HuggingFace at
+    ``https://huggingface.co/light-curve/astromer1`` (``astromer1.onnx``).
+    Three named outputs are available; select with the ``output`` parameter:
+
+    * ``"mean"`` (default) — masked mean pooling → shape ``(batch, 256)``
+    * ``"max"`` — masked max pooling → shape ``(batch, 256)``
+    * ``"sequence"`` — per-timestep features → shape ``(batch, 200, 256)``
+
+    Use :meth:`from_hf` to download and load the model directly.
+
+    Parameters
+    ----------
+    session :
+        ONNX inference session for the Astromer 1 model file.
+    output : str, optional
+        Which named output to return: ``"mean"``, ``"max"``, or ``"sequence"``.
+        Defaults to ``"mean"``.
+    bands : sequence of str or int, optional
+        Band labels.  ``None`` (default) treats the whole light curve as one
+        band.
+    reduction : str, list of str, or Reduction
+        Windowing strategy.  Defaults to :class:`NonOverlappingWindows`.
+    """
+
+    _HF_REPO = "light-curve/astromer1"
+
+
+class Astromer2(_AstromerModel):
+    """Astromer 2 embedding model (Donoso-Oliva et al. 2026).
+
+    Pretrained on 1.5 million MACHO light curves.  Accepts irregularly-sampled
+    single-band photometry and returns a 256-dimensional embedding.
+
+    The ONNX model is hosted on HuggingFace at
+    ``https://huggingface.co/light-curve/astromer2`` (``astromer2.onnx``).
+    Three named outputs are available; select with the ``output`` parameter:
+
+    * ``"mean"`` (default) — masked mean pooling → shape ``(batch, 256)``
+    * ``"max"`` — masked max pooling → shape ``(batch, 256)``
+    * ``"sequence"`` — per-timestep features → shape ``(batch, 200, 256)``
+
+    Use :meth:`from_hf` to download and load the model directly.
+
+    Parameters
+    ----------
+    session :
+        ONNX inference session for the Astromer 2 model file.
+    output : str, optional
+        Which named output to return: ``"mean"``, ``"max"``, or ``"sequence"``.
+        Defaults to ``"mean"``.
+    bands : sequence of str or int, optional
+        Band labels.  ``None`` (default) treats the whole light curve as one
+        band.
+    reduction : str, list of str, or Reduction
+        Windowing strategy.  Defaults to :class:`NonOverlappingWindows`, which
+        matches the sequential-window preprocessing used to produce the reference
+        embeddings on HuggingFace.
+    """
+
+    _HF_REPO = "light-curve/astromer2"