# Copyright 2021 The QHBM Library Authors. All Rights Reserved.
#
# 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
#
# https://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.
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# ==============================================================================
"""Utilities for metrics on BitstringEnergy."""
import itertools
import tensorflow as tf
from qhbmlib.models import energy
[docs]def probabilities(input_energy: energy.BitstringEnergy):
"""Returns the probabilities of the EBM.
Args:
input_energy: The energy function defining the EBM.
"""
all_bitstrings = tf.constant(
list(itertools.product([0, 1], repeat=input_energy.num_bits)),
dtype=tf.int8)
all_energies = input_energy(all_bitstrings)
energy_exp = tf.math.exp(-all_energies)
partition = tf.math.reduce_sum(energy_exp)
return energy_exp / partition