# Copyright (c) Facebook, Inc. and its affiliates.
#
# This source code is licensed under the MIT license found in the
# LICENSE file in the root directory of this source tree.

import collections
import os
import shutil
import tempfile
import unittest

import numpy as np
import torch
from scripts.average_checkpoints import average_checkpoints
from torch import nn


class ModelWithSharedParameter(nn.Module):
    def __init__(self):
        super(ModelWithSharedParameter, self).__init__()
        self.embedding = nn.Embedding(1000, 200)
        self.FC1 = nn.Linear(200, 200)
        self.FC2 = nn.Linear(200, 200)
        # tie weight in FC2 to FC1
        self.FC2.weight = nn.Parameter(self.FC1.weight)
        self.FC2.bias = nn.Parameter(self.FC1.bias)

        self.relu = nn.ReLU()

    def forward(self, input):
        return self.FC2(self.ReLU(self.FC1(input))) + self.FC1(input)


class TestAverageCheckpoints(unittest.TestCase):
    def test_average_checkpoints(self):
        params_0 = collections.OrderedDict(
            [
                ("a", torch.DoubleTensor([100.0])),
                ("b", torch.FloatTensor([[1.0, 2.0, 3.0], [4.0, 5.0, 6.0]])),
                ("c", torch.IntTensor([7, 8, 9])),
            ]
        )
        params_1 = collections.OrderedDict(
            [
                ("a", torch.DoubleTensor([1.0])),
                ("b", torch.FloatTensor([[1.0, 1.0, 1.0], [1.0, 1.0, 1.0]])),
                ("c", torch.IntTensor([2, 2, 2])),
            ]
        )
        params_avg = collections.OrderedDict(
            [
                ("a", torch.DoubleTensor([50.5])),
                ("b", torch.FloatTensor([[1.0, 1.5, 2.0], [2.5, 3.0, 3.5]])),
                # We expect truncation for integer division
                ("c", torch.IntTensor([4, 5, 5])),
            ]
        )

        fd_0, path_0 = tempfile.mkstemp()
        fd_1, path_1 = tempfile.mkstemp()
        torch.save(collections.OrderedDict([("model", params_0)]), path_0)
        torch.save(collections.OrderedDict([("model", params_1)]), path_1)

        output = average_checkpoints([path_0, path_1])["model"]

        os.close(fd_0)
        os.remove(path_0)
        os.close(fd_1)
        os.remove(path_1)

        for (k_expected, v_expected), (k_out, v_out) in zip(
            params_avg.items(), output.items()
        ):
            self.assertEqual(
                k_expected,
                k_out,
                "Key mismatch - expected {} but found {}. "
                "(Expected list of keys: {} vs actual list of keys: {})".format(
                    k_expected, k_out, params_avg.keys(), output.keys()
                ),
            )
            np.testing.assert_allclose(
                v_expected.numpy(),
                v_out.numpy(),
                err_msg="Tensor value mismatch for key {}".format(k_expected),
            )

    def test_average_checkpoints_with_shared_parameters(self):
        def _construct_model_with_shared_parameters(path, value):
            m = ModelWithSharedParameter()
            nn.init.constant_(m.FC1.weight, value)
            torch.save({"model": m.state_dict()}, path)
            return m

        tmpdir = tempfile.mkdtemp()
        paths = []
        path = os.path.join(tmpdir, "m1.pt")
        m1 = _construct_model_with_shared_parameters(path, 1.0)
        paths.append(path)

        path = os.path.join(tmpdir, "m2.pt")
        m2 = _construct_model_with_shared_parameters(path, 2.0)
        paths.append(path)

        path = os.path.join(tmpdir, "m3.pt")
        m3 = _construct_model_with_shared_parameters(path, 3.0)
        paths.append(path)

        new_model = average_checkpoints(paths)
        self.assertTrue(
            torch.equal(
                new_model["model"]["embedding.weight"],
                (m1.embedding.weight + m2.embedding.weight + m3.embedding.weight) / 3.0,
            )
        )

        self.assertTrue(
            torch.equal(
                new_model["model"]["FC1.weight"],
                (m1.FC1.weight + m2.FC1.weight + m3.FC1.weight) / 3.0,
            )
        )

        self.assertTrue(
            torch.equal(
                new_model["model"]["FC2.weight"],
                (m1.FC2.weight + m2.FC2.weight + m3.FC2.weight) / 3.0,
            )
        )
        shutil.rmtree(tmpdir)


if __name__ == "__main__":
    unittest.main()