DeePMD-kit Python Inference

Load a trained DeePMD-kit model in Python and predict energy, forces, and virial for atomic configurations. Also covers CLI-based testing with dp test.

Quick Start

from deepmd.infer import DeepPot
import numpy as np

dp = DeepPot("model.pth")
coord = np.array([[1, 0, 0], [0, 0, 1.5], [1, 0, 3]]).reshape([1, -1])
cell = np.diag(10 * np.ones(3)).reshape([1, -1])
atype = [1, 0, 1]
e, f, v = dp.eval(coord, cell, atype)

Agent Responsibilities

1. Determine the model source:
   • Frozen model file (.pth for PyTorch, .pb for TensorFlow)
   • Built-in pretrained model name (e.g., DPA-3.2-5M)
   • Checkpoint file (requires freezing first)
2. Determine the inference task:
   • Single-frame prediction (energy, force, virial)
   • Batch prediction over multiple frames
   • Descriptor evaluation
   • Model deviation calculation
   • CLI-based testing against labeled data
3. Help the user prepare input arrays in the correct format.
4. Run inference and report results.

Python API: DeepPot

Load a Model

from deepmd.infer import DeepPot

# From a frozen PyTorch model
dp = DeepPot("model.pth")

# From a frozen TensorFlow model
dp = DeepPot("graph.pb")

# From a built-in pretrained model (auto-downloads if not cached)
dp = DeepPot("DPA-3.2-5M")

Built-in pretrained model names include DPA-3.3-1M, DPA-3.2-5M, DPA-3.1-3M, DPA3-Omol-Large, etc. DeePMD-kit will automatically download and cache the model on first use.

Predict Energy, Forces, and Virial

import numpy as np
from deepmd.infer import DeepPot

dp = DeepPot("model.pth")

# Prepare inputs
# coord: (nframes, natoms * 3) in Angstrom
# cell: (nframes, 9) cell vectors in Angstrom, row-major
# atype: list of atom type indices (length natoms)

coord = np.array(
    [
        [
            0.0,
            0.0,
            0.0,  # atom 0 (O)
            0.0,
            0.0,
            1.0,  # atom 1 (H)
            0.0,
            1.0,
            0.0,
        ]  # atom 2 (H)
    ]
).reshape([1, -1])

cell = np.diag([10.0, 10.0, 10.0]).reshape([1, -1])

# atype indices correspond to type_map order in the model
# e.g., if type_map = ["O", "H"], then O=0, H=1
atype = [0, 1, 1]

e, f, v = dp.eval(coord, cell, atype)

print(f"Energy (eV): {e}")  # shape: (nframes, 1)
print(f"Forces (eV/A): {f}")  # shape: (nframes, natoms, 3)
print(f"Virial (eV): {v}")  # shape: (nframes, 9)

Non-periodic Systems

For non-periodic (isolated) systems, pass cell=None:

e, f, v = dp.eval(coord, None, atype)

Batch Prediction

Process multiple frames at once:

nframes = 10
natoms = 3

coords = np.random.rand(nframes, natoms * 3)
cells = np.tile(np.diag([10.0, 10.0, 10.0]).reshape([1, -1]), (nframes, 1))
atype = [0, 1, 1]

e, f, v = dp.eval(coords, cells, atype)
# e: (nframes, 1)
# f: (nframes, natoms, 3)
# v: (nframes, 9)

Evaluate Descriptors

Extract the descriptor (atomic environment representation) from the model:

descriptors = dp.eval_descriptor(coord, cell, atype)
# shape: (nframes, natoms, ndesc)

This can also be done via CLI:

dp eval-desc -m model.pth -s /path/to/system -o desc_output

Calculate Model Deviation

Compare predictions from multiple models to estimate uncertainty:

from deepmd.infer import calc_model_devi, DeepPot

coord = np.array([[1, 0, 0], [0, 0, 1.5], [1, 0, 3]]).reshape([1, -1])
cell = np.diag(10 * np.ones(3)).reshape([1, -1])
atype = [1, 0, 1]

graphs = [DeepPot("model_0.pth"), DeepPot("model_1.pth")]
model_devi = calc_model_devi(coord, cell, atype, graphs)

Important: avoid loading the same model multiple times in a loop, as this can cause memory leaks.

CLI Testing: dp test

Test a frozen model against labeled data:

# Basic test
dp --pt test -m model.pth -s /path/to/test_system -n 30

# Test with detailed output
dp --pt test -m model.pth -s /path/to/test_system -n 30 -d test_detail

dp test Options

Option	Description
-m MODEL	Path to the frozen model file
-s SYSTEM	Path to the test data system
-n NUMB	Number of test frames
-d DETAIL	Output prefix for detailed results
--shuffle-test	Shuffle test frames

Output

dp test prints RMSE values for energy, force, and virial:

Energy RMSE        : 1.234e-03 eV
Energy RMSE/Natoms : 6.427e-06 eV
Force  RMSE        : 2.345e-02 eV/A
Virial RMSE        : 5.678e-02 eV
Virial RMSE/Natoms : 2.957e-04 eV

With -d test_detail, per-frame predictions are saved to files for further analysis.

Complete Example: Train, Freeze, and Inference

import subprocess
import numpy as np
from deepmd.infer import DeepPot

# Step 1: Train (run in shell)
# dp --pt train input.json

# Step 2: Freeze (run in shell)
# dp --pt freeze -o model.pth

# Step 3: Python inference
dp = DeepPot("model.pth")

# Load test data from deepmd format
coord = np.load("test_system/set.000/coord.npy")  # (nframes, natoms*3)
cell = np.load("test_system/set.000/box.npy")  # (nframes, 9)
atype_raw = np.loadtxt("test_system/type.raw", dtype=int).tolist()

# Predict
e, f, v = dp.eval(coord, cell, atype_raw)

# Compare with reference
ref_energy = np.load("test_system/set.000/energy.npy")
ref_force = np.load("test_system/set.000/force.npy")

natoms = len(atype_raw)
energy_rmse = np.sqrt(np.mean((e.flatten() - ref_energy.flatten()) ** 2)) / natoms
force_rmse = np.sqrt(np.mean((f.reshape(-1) - ref_force.reshape(-1)) ** 2))

print(f"Energy RMSE/atom: {energy_rmse:.6f} eV")
print(f"Force RMSE:       {force_rmse:.6f} eV/A")

Using Pretrained Models Directly

Built-in pretrained models can be used without any training:

from deepmd.infer import DeepPot
import numpy as np

# Auto-downloads DPA-3.2-5M on first use
dp = DeepPot("DPA-3.2-5M")

# Water molecule example
coord = np.array(
    [
        [0.000, 0.000, 0.117],  # O
        [0.000, 0.757, -0.469],  # H
        [0.000, -0.757, -0.469],  # H
    ]
).reshape([1, -1])

cell = np.diag([10.0, 10.0, 10.0]).reshape([1, -1])
atype = [0, 1, 1]  # Check model's type_map for correct indices

e, f, v = dp.eval(coord, cell, atype)
print(f"Energy: {e[0][0]:.6f} eV")
print(f"Forces:\n{f[0]}")

To download pretrained models explicitly:

dp pretrained download DPA-3.3-1M
dp pretrained download DPA-3.2-5M
dp pretrained download DPA-3.1-3M
dp pretrained download DPA-3.2-5M --cache-dir ./models

Input Array Format Reference

Array	Shape	Unit	Description
coord	(nframes, natoms*3)	Angstrom	Atomic coordinates, flattened
cell	(nframes, 9)	Angstrom	Cell vectors, row-major (a1x,a1y,a1z,a2x,...)
atype	(natoms,)	-	Atom type indices matching model's type_map

Output	Shape	Unit	Description
e	(nframes, 1)	eV	Total energy per frame
f	(nframes, natoms, 3)	eV/A	Forces on each atom
v	(nframes, 9)	eV	Virial tensor per frame

Agent Checklist

• Model file exists and is accessible (.pth, .pb, or valid pretrained name)
• coord array is shaped (nframes, natoms*3) and in Angstrom
• cell array is shaped (nframes, 9) or None for non-periodic systems
• atype indices match the model's type_map ordering
• For model deviation, multiple models are loaded only once (not in a loop)
• Results are reported with correct units (eV, eV/A)

References

• Python inference documentation
• dp test documentation
• Pretrained model download
• DeepPot API reference
• DeePMD-kit GitHub