Feat: Refactor dipole fitting pytorch (deepmodeling#3281)

This PR is to provide implementation of equivariant diplole fitting in
pytorch and backend-independent numpy.

---------

Signed-off-by: Anyang Peng <[email protected]>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

deepmd/dpmodel/fitting/__init__.py

@@ -1,4 +1,7 @@
 # SPDX-License-Identifier: LGPL-3.0-or-later
+from .dipole_fitting import (
+    DipoleFitting,
+)
 from .invar_fitting import (
     InvarFitting,
 )
@@ -9,4 +12,5 @@
 __all__ = [
     "InvarFitting",
     "make_base_fitting",
+    "DipoleFitting",
 ]

deepmd/dpmodel/fitting/dipole_fitting.py

@@ -0,0 +1,199 @@
+# SPDX-License-Identifier: LGPL-3.0-or-later
+from typing import (
+    Any,
+    Dict,
+    List,
+    Optional,
+)
+
+import numpy as np
+
+from deepmd.dpmodel import (
+    DEFAULT_PRECISION,
+)
+from deepmd.dpmodel.output_def import (
+    FittingOutputDef,
+    OutputVariableDef,
+    fitting_check_output,
+)
+
+from .general_fitting import (
+    GeneralFitting,
+)
+
+
+@fitting_check_output
+class DipoleFitting(GeneralFitting):
+    r"""Fitting rotationally invariant diploe of the system.
+
+    Parameters
+    ----------
+    var_name
+            The name of the output variable.
+    ntypes
+            The number of atom types.
+    dim_descrpt
+            The dimension of the input descriptor.
+    dim_rot_mat : int
+        The dimension of rotation matrix, m1.
+    neuron
+            Number of neurons :math:`N` in each hidden layer of the fitting net
+    resnet_dt
+            Time-step `dt` in the resnet construction:
+            :math:`y = x + dt * \phi (Wx + b)`
+    numb_fparam
+            Number of frame parameter
+    numb_aparam
+            Number of atomic parameter
+    rcond
+            The condition number for the regression of atomic energy.
+    tot_ener_zero
+            Force the total energy to zero. Useful for the charge fitting.
+    trainable
+            If the weights of fitting net are trainable.
+            Suppose that we have :math:`N_l` hidden layers in the fitting net,
+            this list is of length :math:`N_l + 1`, specifying if the hidden layers and the output layer are trainable.
+    atom_ener
+            Specifying atomic energy contribution in vacuum. The `set_davg_zero` key in the descrptor should be set.
+    activation_function
+            The activation function :math:`\boldsymbol{\phi}` in the embedding net. Supported options are |ACTIVATION_FN|
+    precision
+            The precision of the embedding net parameters. Supported options are |PRECISION|
+    layer_name : list[Optional[str]], optional
+            The name of the each layer. If two layers, either in the same fitting or different fittings,
+            have the same name, they will share the same neural network parameters.
+    use_aparam_as_mask: bool, optional
+            If True, the atomic parameters will be used as a mask that determines the atom is real/virtual.
+            And the aparam will not be used as the atomic parameters for embedding.
+    distinguish_types
+            Different atomic types uses different fitting net.
+
+    """
+
+    def __init__(
+        self,
+        var_name: str,
+        ntypes: int,
+        dim_descrpt: int,
+        dim_rot_mat: int,
+        neuron: List[int] = [120, 120, 120],
+        resnet_dt: bool = True,
+        numb_fparam: int = 0,
+        numb_aparam: int = 0,
+        rcond: Optional[float] = None,
+        tot_ener_zero: bool = False,
+        trainable: Optional[List[bool]] = None,
+        atom_ener: Optional[List[Optional[float]]] = None,
+        activation_function: str = "tanh",
+        precision: str = DEFAULT_PRECISION,
+        layer_name: Optional[List[Optional[str]]] = None,
+        use_aparam_as_mask: bool = False,
+        spin: Any = None,
+        distinguish_types: bool = False,
+        exclude_types: List[int] = [],
+        old_impl=False,
+    ):
+        # seed, uniform_seed are not included
+        if tot_ener_zero:
+            raise NotImplementedError("tot_ener_zero is not implemented")
+        if spin is not None:
+            raise NotImplementedError("spin is not implemented")
+        if use_aparam_as_mask:
+            raise NotImplementedError("use_aparam_as_mask is not implemented")
+        if layer_name is not None:
+            raise NotImplementedError("layer_name is not implemented")
+        if atom_ener is not None:
+            raise NotImplementedError("atom_ener is not implemented")
+
+        self.dim_rot_mat = dim_rot_mat
+        super().__init__(
+            var_name=var_name,
+            ntypes=ntypes,
+            dim_descrpt=dim_descrpt,
+            neuron=neuron,
+            resnet_dt=resnet_dt,
+            numb_fparam=numb_fparam,
+            numb_aparam=numb_aparam,
+            rcond=rcond,
+            tot_ener_zero=tot_ener_zero,
+            trainable=trainable,
+            atom_ener=atom_ener,
+            activation_function=activation_function,
+            precision=precision,
+            layer_name=layer_name,
+            use_aparam_as_mask=use_aparam_as_mask,
+            spin=spin,
+            distinguish_types=distinguish_types,
+            exclude_types=exclude_types,
+        )
+        self.old_impl = False
+
+    def _net_out_dim(self):
+        """Set the FittingNet output dim."""
+        return self.dim_rot_mat
+
+    def serialize(self) -> dict:
+        data = super().serialize()
+        data["dim_rot_mat"] = self.dim_rot_mat
+        data["old_impl"] = self.old_impl
+        return data
+
+    def output_def(self):
+        return FittingOutputDef(
+            [
+                OutputVariableDef(
+                    self.var_name,
+                    [3],
+                    reduciable=True,
+                    r_differentiable=True,
+                    c_differentiable=True,
+                ),
+            ]
+        )
+
+    def call(
+        self,
+        descriptor: np.ndarray,
+        atype: np.ndarray,
+        gr: Optional[np.ndarray] = None,
+        g2: Optional[np.ndarray] = None,
+        h2: Optional[np.ndarray] = None,
+        fparam: Optional[np.ndarray] = None,
+        aparam: Optional[np.ndarray] = None,
+    ) -> Dict[str, np.ndarray]:
+        """Calculate the fitting.
+
+        Parameters
+        ----------
+        descriptor
+            input descriptor. shape: nf x nloc x nd
+        atype
+            the atom type. shape: nf x nloc
+        gr
+            The rotationally equivariant and permutationally invariant single particle
+            representation. shape: nf x nloc x ng x 3
+        g2
+            The rotationally invariant pair-partical representation.
+            shape: nf x nloc x nnei x ng
+        h2
+            The rotationally equivariant pair-partical representation.
+            shape: nf x nloc x nnei x 3
+        fparam
+            The frame parameter. shape: nf x nfp. nfp being `numb_fparam`
+        aparam
+            The atomic parameter. shape: nf x nloc x nap. nap being `numb_aparam`
+
+        """
+        nframes, nloc, _ = descriptor.shape
+        assert gr is not None, "Must provide the rotation matrix for dipole fitting."
+        # (nframes, nloc, m1)
+        out = self._call_common(descriptor, atype, gr, g2, h2, fparam, aparam)[
+            self.var_name
+        ]
+        # (nframes * nloc, 1, m1)
+        out = out.reshape(-1, 1, self.dim_rot_mat)
+        # (nframes * nloc, m1, 3)
+        gr = gr.reshape(nframes * nloc, -1, 3)
+        # (nframes, nloc, 3)
+        out = np.einsum("bim,bmj->bij", out, gr).squeeze(-2).reshape(nframes, nloc, 3)
+        return {self.var_name: out}