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

# Copyright 2019 Kakao Brain
#
# 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
#
#   http://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.
# See the License for the specific language governing permissions and
# limitations under the License.

from collections import OrderedDict
from copy import deepcopy
import os
import time
from typing import Tuple

from packaging import version
import pytest
import torch
from torch import nn

from fairscale.nn.model_parallel.initialize import (
    destroy_model_parallel,
    get_pipeline_parallel_group,
    initialize_model_parallel,
)
from fairscale.nn.pipe import LazyModule, Pipe
from tests.nn.model_parallel.commons import get_worker_map, set_random_seed, torch_spawn


@torch_spawn([2])
@pytest.mark.parametrize("pipeline_style", [Pipe.MultiProcess, Pipe.AsyncSchedule])
def parameters(pipeline_style):
    model = nn.Sequential(nn.Linear(1, 1))
    pipe = Pipe(model, balance=[1], style=pipeline_style, worker_map=get_worker_map(), chunks=1)
    if torch.distributed.get_rank() == 0:
        assert list(pipe.parameters()) != []
    else:
        assert list(pipe.parameters()) == []


@torch_spawn([2])
@pytest.mark.skipif(not torch.cuda.is_available(), reason="cuda required")
def infiniband():
    if torch.distributed.get_rank() == 0:
        t = torch.Tensor(range(100)).cuda()
        torch.distributed.broadcast(t, 0)
    else:
        t = torch.empty(100).cuda()
        torch.distributed.broadcast(t, 0)

    assert torch.equal(t, torch.Tensor(range(100)).cuda())
    print(f"t on {torch.distributed.get_rank()} is {t}")


@torch_spawn([2])
@pytest.mark.skipif("OMPI_COMM_WORLD_RANK" not in os.environ, reason="mpi required")
@pytest.mark.skipif(not torch.cuda.is_available(), reason="cuda required")
def infiniband2():
    if torch.distributed.get_rank() == 0:
        t = torch.Tensor(range(100)).cuda()
        torch.distributed.send(t, 1, group=get_pipeline_parallel_group())
    else:
        t = torch.empty(100).cuda()
        torch.distributed.recv(t, 0, group=get_pipeline_parallel_group())

    assert torch.equal(t, torch.Tensor(range(100)).cuda())
    print(f"t on {torch.distributed.get_rank()} is {t}")


@torch_spawn([2])
@pytest.mark.skipif(not torch.cuda.is_available(), reason="cuda required")
def infiniband3():
    t = torch.Tensor(range(100)).cuda()
    torch.distributed.all_reduce(t, op=torch.distributed.ReduceOp.SUM)
    assert torch.equal(t, torch.Tensor(range(0, 200, 2)).cuda())


@torch_spawn([2])
@pytest.mark.skipif("OMPI_COMM_WORLD_RANK" not in os.environ, reason="mpi required")
def mpi():
    seed = 1234
    torch.manual_seed(seed)
    torch.cuda.manual_seed(seed)

    torch.distributed.barrier()
    tensor_size = (1024, 1024, 10)
    torch.cuda.set_device(torch.distributed.get_rank())  # need to pin device or ucx gets unhappy

    if torch.distributed.get_rank() == 0:
        # t = torch.Tensor(range(10)).cuda(0)
        t = torch.rand(*tensor_size).cuda(0)
        torch.distributed.send(t, 1, tag=1234)
    else:
        t = torch.empty(*tensor_size).cuda(1)
        torch.distributed.recv(t, 0, tag=1234)
        t2 = torch.rand(*tensor_size).cuda(1)

        assert torch.equal(t, t2)


@torch_spawn([1])
@pytest.mark.parametrize("pipeline_style", [Pipe.MultiProcess, Pipe.AsyncSchedule])
def public_attrs(pipeline_style):
    class MyString:
        def __init__(self, value):
            self.value = value

        def __str__(self):
            return self.value

    model = nn.Sequential(nn.Linear(1, 1))

    pipe = Pipe(
        model,
        balance=(1,),
        style=pipeline_style,
        worker_map=get_worker_map(),
        chunks=42.000,
        checkpoint=MyString("always"),
    )

    print(f"balance = {pipe.devices}")
    assert pipe.balance == [1]
    assert pipe.devices is None
    assert pipe.chunks == 42
    assert isinstance(pipe.chunks, int)
    assert pipe.checkpoint == "always"
    assert isinstance(pipe.checkpoint, str)


@torch_spawn([2])
@pytest.mark.parametrize("balance", [[2], [1, 1]])
@pytest.mark.parametrize("pipeline_style", [Pipe.MultiProcess, Pipe.AsyncSchedule])
def sequential_like(balance, pipeline_style):
    a = nn.Linear(1, 1)
    b = nn.Linear(1, 1)

    model = nn.Sequential(a, b)
    model = Pipe(model, balance, style=pipeline_style, worker_map=get_worker_map())

    if balance == [2]:
        if torch.distributed.get_rank() == 0:
            assert len(model) == 2
            assert list(model) == [a, b]

            assert model[0] is a
            assert model[1] is b
            with pytest.raises(IndexError):
                _ = model[2]

            assert model[-1] is b
            assert model[-2] is a
        else:
            assert len(model) == 0
            assert list(model) == []
    else:
        assert len(model) == 1
        if torch.distributed.get_rank() == 0:
            assert list(model) == [a]
            assert model[0] is a
            assert model[-1] is a
        else:
            assert list(model) == [b]
            assert model[0] is b
            assert model[-1] is b

        with pytest.raises(IndexError):
            _ = model[1]


@torch_spawn([1])
@pytest.mark.parametrize("pipeline_style", [Pipe.MultiProcess, Pipe.AsyncSchedule])
def balance_wrong_length(pipeline_style):
    a = nn.Linear(1, 1)
    b = nn.Linear(1, 1)

    model = nn.Sequential(a, b)

    with pytest.raises(ValueError):
        Pipe(model, balance=[1], style=pipeline_style, worker_map=get_worker_map())

    with pytest.raises(ValueError):
        Pipe(model, balance=[3], style=pipeline_style, worker_map=get_worker_map())


@torch_spawn([2])
@pytest.mark.parametrize("pipeline_style", [Pipe.MultiProcess, Pipe.AsyncSchedule])
def balance_less_than_1(pipeline_style):
    a = nn.Linear(1, 1)
    b = nn.Linear(1, 1)

    model = nn.Sequential(a, b)

    with pytest.raises(ValueError):
        Pipe(model, balance=[0, 2], style=pipeline_style, worker_map=get_worker_map())

    with pytest.raises(ValueError):
        Pipe(model, balance=[-1, 3], style=pipeline_style, worker_map=get_worker_map())


@torch_spawn([1])
@pytest.mark.parametrize("pipeline_style", [Pipe.MultiProcess, Pipe.AsyncSchedule])
def chunks_less_than_1(pipeline_style):
    model = nn.Sequential(nn.Linear(1, 1))

    with pytest.raises(ValueError):
        Pipe(model, balance=[1], style=pipeline_style, worker_map=get_worker_map(), chunks=0)

    with pytest.raises(ValueError):
        Pipe(model, balance=[1], style=pipeline_style, worker_map=get_worker_map(), chunks=-1)


@torch_spawn([1])
@pytest.mark.parametrize("pipeline_style", [Pipe.MultiProcess, Pipe.AsyncSchedule])
def too_few_devices(pipeline_style):
    model = nn.Sequential(nn.Linear(1, 1), nn.Linear(1, 1), nn.Linear(1, 1), nn.Linear(1, 1))

    with pytest.raises(IndexError):
        # len(balance) > len(group.size())
        model = Pipe(model, balance=[1, 1, 1, 1], style=pipeline_style, worker_map=get_worker_map())


@torch_spawn([1])
@pytest.mark.parametrize("pipeline_style", [Pipe.MultiProcess, Pipe.AsyncSchedule])
def batch_size_indivisible(pipeline_style):
    model = nn.Sequential(nn.Linear(1, 1))
    model = Pipe(model, balance=[1], style=pipeline_style, worker_map=get_worker_map(), chunks=4)

    with pytest.warns(None) as record:
        model(torch.rand(7, 1))

    # Indivisible batch size is legal.
    assert not record


@torch_spawn([1])
@pytest.mark.parametrize("pipeline_style", [Pipe.MultiProcess, Pipe.AsyncSchedule])
def batch_size_small(pipeline_style):
    model = nn.Sequential(nn.Linear(1, 1))
    model = Pipe(model, balance=[1], style=pipeline_style, worker_map=get_worker_map(), chunks=4)

    with pytest.warns(None) as record:
        model(torch.rand(2, 1))

    # Batch size smaller than chunks is legal.
    assert not record


@torch_spawn([1])
@pytest.mark.parametrize("pipeline_style", [Pipe.MultiProcess, Pipe.AsyncSchedule])
def checkpoint_mode(pipeline_style):
    def count_grad_fn(grad_fn, name, visited=set()):
        if grad_fn in visited:
            return 0
        visited.add(grad_fn)

        if grad_fn is None:
            return 0
        if grad_fn.__class__.__name__ == name:
            return 1

        counter = 0
        for next_grad_fn, _ in grad_fn.next_functions:
            counter += count_grad_fn(next_grad_fn, name, visited=visited)
        return counter

    model = nn.Sequential(nn.Linear(1, 1))
    input = torch.rand(2, 1)

    always = Pipe(
        model,
        balance=[1],
        style=pipeline_style,
        worker_map=get_worker_map(),
        chunks=2,
        checkpoint="always",
        pipelined_backward=False,
    )
    except_last = Pipe(
        model,
        balance=[1],
        style=pipeline_style,
        worker_map=get_worker_map(),
        chunks=2,
        checkpoint="except_last",
        pipelined_backward=False,
    )
    never = Pipe(
        model,
        balance=[1],
        style=pipeline_style,
        worker_map=get_worker_map(),
        chunks=2,
        checkpoint="never",
        pipelined_backward=False,
    )

    always_output = always(input)
    except_last_output = except_last(input)
    never_output = never(input)

    assert count_grad_fn(always_output.grad_fn, "CheckpointBackward") == 2
    assert count_grad_fn(except_last_output.grad_fn, "CheckpointBackward") == 1
    assert count_grad_fn(never_output.grad_fn, "CheckpointBackward") == 0


@torch_spawn([1])
@pytest.mark.parametrize("pipeline_style", [Pipe.MultiProcess, Pipe.AsyncSchedule])
def checkpoint_mode_invalid(pipeline_style):
    model = nn.Sequential(nn.Linear(1, 1))

    with pytest.raises(ValueError, match="checkpoint is not one of 'always', 'except_last', or 'never'"):
        Pipe(
            model,
            balance=[1],
            style=pipeline_style,
            worker_map=get_worker_map(),
            chunks=2,
            checkpoint="INVALID_CHECKPOINT",
        )


@torch_spawn([1])
@pytest.mark.parametrize("pipeline_style", [Pipe.MultiProcess, Pipe.AsyncSchedule])
def checkpoint_mode_when_chunks_1(pipeline_style):
    model = nn.Sequential(nn.Linear(1, 1))

    # All checkpoint modes are fine.
    Pipe(
        model, balance=[1], style=pipeline_style, worker_map=get_worker_map(), chunks=1, checkpoint="except_last",
    )
    Pipe(model, balance=[1], style=pipeline_style, worker_map=get_worker_map(), chunks=1, checkpoint="always")
    Pipe(model, balance=[1], style=pipeline_style, worker_map=get_worker_map(), chunks=1, checkpoint="never")


@torch_spawn([1])
@pytest.mark.parametrize("pipeline_style", [Pipe.MultiProcess, Pipe.AsyncSchedule])
def checkpoint_eval(pipeline_style):
    model = nn.Sequential(nn.Linear(1, 1))
    model = Pipe(
        model, balance=[1], style=pipeline_style, worker_map=get_worker_map(), chunks=2, pipelined_backward=False,
    )
    input = torch.rand(2, 1)

    def find_grad_fn(grad_fn, name):
        if grad_fn is None:
            return False
        if grad_fn.__class__.__name__ == name:
            return True
        for next_grad_fn, _ in grad_fn.next_functions:
            if find_grad_fn(next_grad_fn, name):
                return True
        return False

    model.train()
    train_output = model(input)
    assert find_grad_fn(train_output.grad_fn, "CheckpointBackward")
    assert find_grad_fn(train_output.grad_fn, "RecomputeBackward")

    model.eval()
    eval_output = model(input)
    assert not find_grad_fn(eval_output.grad_fn, "CheckpointBackward")
    assert not find_grad_fn(eval_output.grad_fn, "RecomputeBackward")


def torch_version() -> Tuple[int, ...]:
    result = version.parse(torch.__version__).release
    assert result
    return result


@torch_spawn([2])
@pytest.mark.xfail(torch_version() < (1, 6, 0), reason="Doesn't work on torch < 1.6.0", strict=True)
@pytest.mark.parametrize("pipeline_style", [Pipe.MultiProcess, Pipe.AsyncSchedule])
def checkpoint_non_float_input(pipeline_style):
    class ForkNonFloat(nn.Module):
        def forward(self, input):
            return (input * 2, torch.tensor([False]))

    class JoinNonFloat(nn.Module):
        def forward(self, input):
            return input[0] * 2

    model = nn.Sequential(ForkNonFloat(), JoinNonFloat())
    model = Pipe(
        model,
        balance=[1, 1],
        style=pipeline_style,
        worker_map=get_worker_map(),
        chunks=1,
        checkpoint="always",
        pipelined_backward=False,
    )

    input = torch.rand(1, requires_grad=True)
    output = model(input)
    if model.group.rank() == 1:
        # with torch.autograd.detect_anomaly():
        output.backward()
    elif pipeline_style == Pipe.MultiProcess:
        model.back_helper(output)

    torch.distributed.barrier()


@torch_spawn([1])
@pytest.mark.parametrize("pipeline_style", [Pipe.MultiProcess, Pipe.AsyncSchedule])
def no_grad(pipeline_style):
    model = nn.Sequential(nn.Linear(1, 1))
    model = Pipe(model, balance=[1], style=pipeline_style, worker_map=get_worker_map(), chunks=2)
    input = torch.rand(2, 1)

    latent = None

    def hook(module, input, output):
        _ = module
        _ = input

        nonlocal latent
        latent = output

    partition = model.mp_partitions[0]
    partition.module.register_forward_hook(hook)

    with torch.no_grad():
        model(input)

    assert latent.grad_fn is None


@torch_spawn([1])
@pytest.mark.parametrize("pipeline_style", [Pipe.MultiProcess, Pipe.AsyncSchedule])
def exception(pipeline_style):
    class ExpectedException(Exception):
        pass

    class Raise(nn.Module):
        def forward(self, *_):
            raise ExpectedException()

    model = nn.Sequential(Raise())
    model = Pipe(model, balance=[1], style=pipeline_style, worker_map=get_worker_map(), chunks=1)

    with pytest.raises(ExpectedException):
        model(torch.rand(1))


# FIXME(tom) should probably signal to all hosts in group to stop
@torch_spawn([4])
@pytest.mark.xfail(strict=True)
@pytest.mark.parametrize("pipeline_style", [Pipe.MultiProcess, Pipe.AsyncSchedule])
def exception_early_stop_asap(pipeline_style):
    """Even the first partitions have finished to process, the partition before
    the failed partition hould be killed as soon as possible.
    """

    class ExpectedExceptio(Exception):
        pass

    class Pass(nn.Module):
        def forward(self, x):
            return x

    counter = 0

    class Counter(nn.Module):
        def forward(self, x):
            time.sleep(0.1)

            nonlocal counter
            counter += 1

            return x

    class Raise(nn.Module):
        def forward(self, x):
            raise ExpectedException()

    model = nn.Sequential(Pass(), Pass(), Counter(), Raise())
    model = Pipe(model, [1, 1, 1, 1], style=pipeline_style, worker_map=get_worker_map(), chunks=3)

    with pytest.raises(ExpectedException):
        model(torch.rand(3))

    # If the early stop doesn't work, it would be 3 instead.
    assert counter == 2


@torch_spawn([1])
@pytest.mark.parametrize("pipeline_style", [Pipe.MultiProcess, Pipe.AsyncSchedule])
def input_pair(pipeline_style):
    class Two(nn.Module):
        def __init__(self):
            super().__init__()
            self.fc_a = nn.Linear(1, 1)
            self.fc_b = nn.Linear(1, 1)

        def forward(self, a_and_b):
            a, b = a_and_b
            return (self.fc_a(a), self.fc_b(b))

    model = nn.Sequential(Two())
    model = Pipe(
        model, balance=[1], style=pipeline_style, worker_map=get_worker_map(), chunks=2, pipelined_backward=False,
    )

    a = torch.rand(10, 1, requires_grad=True)
    b = torch.rand(10, 1, requires_grad=True)

    a_out, b_out = model((a, b))
    loss = (a_out + b_out).mean()
    loss.backward()

    assert a.grad is not None
    assert b.grad is not None


@torch_spawn([1])
@pytest.mark.parametrize("pipeline_style", [Pipe.MultiProcess, Pipe.AsyncSchedule])
def input_singleton(pipeline_style):
    class One(nn.Module):
        def __init__(self):
            super().__init__()
            self.fc = nn.Linear(1, 1)

        def forward(self, only_a):
            (a,) = only_a
            return (self.fc(a),)

    model = nn.Sequential(One())
    model = Pipe(
        model, balance=[1], style=pipeline_style, worker_map=get_worker_map(), chunks=2, pipelined_backward=False,
    )

    a = torch.rand(10, 1, requires_grad=True)

    (a_out,) = model((a,))
    loss = a_out.mean()
    loss.backward()

    assert all(p.grad is not None for p in model.parameters())
    assert a.grad is not None


@torch_spawn([1])
@pytest.mark.parametrize("pipeline_style", [Pipe.MultiProcess, Pipe.AsyncSchedule])
def input_varargs(pipeline_style):
    model = nn.Sequential(nn.Linear(1, 1))
    model = Pipe(model, balance=[1], style=pipeline_style, worker_map=get_worker_map())

    a = torch.rand(1)
    b = torch.rand(1)

    # TypeError: forward() takes 2 positional arguments but 3 were given
    with pytest.raises(TypeError):
        model(a, b)


@torch_spawn([1])
@pytest.mark.parametrize("pipeline_style", [Pipe.MultiProcess, Pipe.AsyncSchedule])
def non_tensor(pipeline_style):
    class NonTensor(nn.Module):
        def forward(self, _):
            return "hello"

    model = nn.Sequential(NonTensor())
    model = Pipe(model, balance=[1], style=pipeline_style, worker_map=get_worker_map())
    x = torch.rand(1)

    # TypeError: expected Tensor as element 0 in argument 0, but got str
    with pytest.raises(TypeError):
        model(x)

    # TypeError: expected Tensor to scatter, but got str
    with pytest.raises(TypeError):
        model("hello")


@torch_spawn([1])
@pytest.mark.parametrize("pipeline_style", [Pipe.MultiProcess, Pipe.AsyncSchedule])
def non_tensor_tuple(pipeline_style):
    class NonTensorTuple(nn.Module):
        def forward(self, x):
            return (x, "hello")

    model = nn.Sequential(NonTensorTuple())
    model = Pipe(model, balance=[1], style=pipeline_style, worker_map=get_worker_map())
    x = torch.rand(1)

    # TypeError: CheckpointBackward.forward: expected Variable (got str) for return value 1
    with pytest.raises(TypeError):
        model(x)

    # TypeError: expected Tensor to scatter, but got str
    with pytest.raises(TypeError):
        model((x, "hello"))


@torch_spawn([1])
@pytest.mark.parametrize("checkpoint", ["never", "always", "except_last"])
@pytest.mark.parametrize("lazy", [True, False])
@pytest.mark.parametrize("pipeline_style", [Pipe.MultiProcess, Pipe.AsyncSchedule])
def deferred_batch_norm(checkpoint, lazy, pipeline_style):
    bn = nn.BatchNorm2d(3)
    pipe_bn = deepcopy(bn)
    pipe_fn = lambda: pipe_bn  # noqa: E731
    if lazy:
        model = [LazyModule(pipe_fn)]
    else:
        model = nn.Sequential(pipe_bn)
    pipe = Pipe(
        model,
        balance=[1],
        style=pipeline_style,
        worker_map=get_worker_map(),
        chunks=2,
        checkpoint=checkpoint,
        deferred_batch_norm=True,
    )

    x = torch.rand(4, 3, 10, 10)
    pipe(x).mean().backward()
    bn(x).mean().backward()

    assert torch.allclose(pipe[0].running_mean, bn.running_mean, atol=1e-4)
    assert torch.allclose(pipe[0].running_var, bn.running_var, atol=1e-4)


@torch_spawn([1])
@pytest.mark.parametrize("checkpoint", ["never", "always"])
@pytest.mark.parametrize("lazy", [True, False])
@pytest.mark.parametrize("pipeline_style", [Pipe.MultiProcess, Pipe.AsyncSchedule])
def deferred_batch_norm_params(checkpoint, lazy, pipeline_style):
    bn = nn.BatchNorm2d(3)
    pipe_bn = deepcopy(bn)
    pipe_fn = lambda: pipe_bn  # noqa: E731
    if lazy:
        model = [LazyModule(pipe_fn)]
    else:
        model = nn.Sequential(pipe_bn)
    pipe = Pipe(
        model,
        balance=[1],
        style=pipeline_style,
        worker_map=get_worker_map(),
        chunks=1,
        checkpoint=checkpoint,
        deferred_batch_norm=True,
    )

    x = torch.rand(4, 3, 10, 10)
    pipe(x).mean().backward()
    bn(x).mean().backward()

    assert pipe[0].weight.grad is not None
    assert pipe[0].bias.grad is not None

    assert torch.allclose(pipe[0].weight.grad, bn.weight.grad, atol=1e-4)
    assert torch.allclose(pipe[0].bias.grad, bn.bias.grad, atol=1e-4)


@torch_spawn([4])
@pytest.mark.parametrize("pipeline_style", [Pipe.MultiProcess, Pipe.AsyncSchedule])
def devices(pipeline_style):
    a = nn.Linear(1, 1)
    b = nn.Linear(1, 1)
    c = nn.Linear(1, 1)

    # There are extra two ranks.
    model = nn.Sequential(a, b, c)
    model = Pipe(model, [1, 1, 1], style=pipeline_style, worker_map=get_worker_map())

    # Extra devices must be discarded.
    if model.group.rank() == 3:
        assert model.pipeline is None


@torch_spawn([2])
@pytest.mark.parametrize("pipeline_style", [Pipe.MultiProcess, Pipe.AsyncSchedule])
def partitions(pipeline_style):
    a = nn.Linear(1, 1)
    b = nn.Linear(1, 1)

    model = nn.Sequential(a, b)
    model = Pipe(model, [1, 1], style=pipeline_style, worker_map=get_worker_map())

    assert isinstance(model.mp_partitions, list)
    assert len(model) == 1
    assert isinstance(model.mp_partitions[0].module, nn.Sequential)

    if model.group.rank() == 0:
        assert "0.0.weight" in model.state_dict()
    else:
        assert "0.1.weight" in model.state_dict()


@torch_spawn([2])
@pytest.mark.skipif(not torch.cuda.is_available(), reason="cuda required")
@pytest.mark.parametrize("pipeline_style", [Pipe.MultiProcess, Pipe.AsyncSchedule])
def deny_moving(pipeline_style):
    a = nn.Linear(1, 1)
    b = nn.Linear(1, 1)

    model = nn.Sequential(a, b)
    model = Pipe(model, [1, 1], style=pipeline_style, worker_map=get_worker_map())

    model.cuda()
    model.cpu()
    model.to(torch.device("cuda"))
    model.to(0)
    model.to("cuda")
    model.to(device=0)
    model.to(torch.rand(1))
    model.to(tensor=torch.rand(1))

    # Casting is allowed.
    model.half()
    model.to(torch.double)
    model.to(dtype=torch.float)


@torch_spawn([1])
@pytest.mark.parametrize("pipeline_style", [Pipe.MultiProcess, Pipe.AsyncSchedule])
def empty_module(pipeline_style):
    # Empty sequential module is not illegal.
    model = nn.Sequential()
    model = Pipe(model, [], style=pipeline_style, worker_map=get_worker_map())

    assert model(torch.tensor([42])) == torch.tensor([42])
    assert model((torch.tensor([42]),)) == (torch.tensor([42]),)

    # But only tensor or tensors is legal in Pipe.

    with pytest.raises(TypeError):
        model(42)


@torch_spawn([2])
@pytest.mark.parametrize("pipeline_style", [Pipe.MultiProcess, Pipe.AsyncSchedule])
def named_children(pipeline_style):
    a = nn.Linear(1, 1)
    b = nn.Linear(1, 1)

    model = nn.Sequential(OrderedDict([("a", a), ("b", b)]))
    model = Pipe(model, [1, 1], style=pipeline_style, worker_map=get_worker_map())

    names = set(n for n, _ in model.named_modules())
    if model.group.rank() == 0:
        assert "0.a" in names
    else:
        assert "0.b" in names

    # Pipe doesn't support __getattr__. Unlike nn.Sequential, Pipe requires
    # several methods in its namespace.
    with pytest.raises(AttributeError):
        model.a


@torch_spawn([1])
@pytest.mark.parametrize("pipeline_style", [Pipe.MultiProcess, Pipe.AsyncSchedule])
def recommend_auto_balance(pipeline_style):
    with pytest.raises(ValueError, match="fairscale.nn.pipe.balance"):
        # balance is required
        Pipe(nn.Sequential())

    with pytest.raises(ValueError, match="fairscale.nn.pipe.balance"):
        # module and sum of balance have differen length (module: 0, sum of balance: 1)
        Pipe(nn.Sequential(), [1])

    with pytest.raises(ValueError, match="fairscale.nn.pipe.balance"):
        # module and sum of balance have different length (module: 2, sum of balance: 1)
        Pipe(nn.Sequential(nn.Linear(1, 1), nn.Linear(1, 1)), [1])


@torch_spawn([2])
@pytest.mark.parametrize("pipeline_style", [Pipe.MultiProcess, Pipe.AsyncSchedule])
def lazy_construction(pipeline_style):
    init_count = 0

    class Custom(nn.Module):
        def __init__(self):
            super(Custom, self).__init__()
            nonlocal init_count
            init_count += 1

        def forward(self, x):
            return x

    model = [
        LazyModule(lambda: Custom()),
        LazyModule(lambda: Custom()),
        LazyModule(lambda: Custom()),
        LazyModule(lambda: Custom()),
    ]

    pipe = Pipe(model, balance=[2, 2], style=pipeline_style, worker_map=get_worker_map())

    assert isinstance(pipe[0], Custom)
    assert isinstance(pipe[1], Custom)
    assert len(pipe) == 2
    assert init_count == 2


@torch_spawn([2])
@pytest.mark.skipif("OMPI_COMM_WORLD_RANK" in os.environ, reason="doesn't apply to mpi")
@pytest.mark.parametrize("pipeline_style", [Pipe.MultiProcess, Pipe.AsyncSchedule])
def missing_worker_map(pipeline_style):
    model = nn.Sequential(nn.ReLU(), nn.ReLU())

    with pytest.raises(ValueError, match="'RpcTransport' requires 'worker_map' to be set"):
        Pipe(model, [1, 1], style=pipeline_style)


@torch_spawn([2])
@pytest.mark.skip(reason="currently broken")
@pytest.mark.parametrize("pipeline_style", [Pipe.MultiProcess, Pipe.AsyncSchedule])
def verify_module_duplicate_parameters_on_distinct_partitions(pipeline_style):
    class Surrogate(nn.Module):
        def __init__(self, module):
            super().__init__()
            self.module = module

    conv = nn.Conv2d(3, 3, 1)
    model = nn.Sequential(Surrogate(conv), Surrogate(conv))

    # FIXME(tom) can't have duplicate params with separate processes
    with pytest.raises(ValueError, match="module with duplicate parameters on distinct devices is not supported"):
        Pipe(model, [1, 1], style=pipeline_style, worker_map=get_worker_map())


@torch_spawn([4])
@pytest.mark.parametrize("pipeline_style", [Pipe.MultiProcess, Pipe.AsyncSchedule])
def pipelined_backward(pipeline_style):
    model = nn.Sequential(nn.ReLU(), nn.ReLU())

    destroy_model_parallel()
    initialize_model_parallel(1, 4)
    pipe = Pipe(model, [1, 1], style=pipeline_style, worker_map=get_worker_map())

    assert pipe.pipelined_backward is False

    destroy_model_parallel()
    initialize_model_parallel(2, 2)
    pipe = Pipe(model, [1, 1], style=pipeline_style, worker_map=get_worker_map())

    assert pipe.pipelined_backward is True


@torch_spawn([4])
def async_event_loop():

    model = nn.Sequential(nn.Linear(10, 10), nn.ReLU(), nn.Linear(10, 10), nn.ReLU())
    pipe = Pipe(model, [1, 1, 1, 1], style=Pipe.AsyncSchedule, worker_map=get_worker_map(), chunks=10)

    inputs = torch.rand(100, 10)

    output = pipe(inputs)
    if pipe.final_stage:
        loss = output.mean()
        loss.backward()


@torch_spawn([4])
def reuse_lazy():
    if False:  # speed
        reused = LazyModule(lambda: nn.Linear(10, 10))
        model = [reused, nn.Linear(10, 10), nn.ReLU(), reused, nn.ReLU(), reused, nn.ReLU()]
        # model = [reused, reused, nn.Linear(10, 10), nn.ReLU(), reused, reused, nn.ReLU(), reused, reused, nn.ReLU()]
        pipe = Pipe(model, [3, 1, 1], style=Pipe.AsyncSchedule, worker_map=get_worker_map())
        pipe.eval()
        output = pipe(torch.rand(10))

        print(f"output on {pipe.group.rank()}, {output}")
        torch.distributed.barrier()

    set_random_seed(1234)
    # test both foward
    reused = nn.Linear(10, 10)
    layers = [reused, nn.Linear(10, 10), nn.ReLU(), reused, nn.ReLU(), reused, nn.ReLU()]
    model = nn.Sequential(*layers)
    model.eval()

    set_random_seed(1234)
    # ensure identical weights but no sharing between model and pipe
    reused = nn.Linear(10, 10)
    layers = [reused, nn.Linear(10, 10), nn.ReLU(), reused, nn.ReLU(), reused, nn.ReLU()]
    pipe = Pipe(layers, [3, 1, 1], style=Pipe.AsyncSchedule, worker_map=get_worker_map())
    pipe.eval()
    model_optimizer = torch.optim.SGD(model.parameters(), lr=0.01, momentum=0.9)
    pipe_optimizer = torch.optim.SGD(pipe.parameters(), lr=0.01, momentum=0.9) if len(list(pipe.parameters())) else None
    inputs = torch.rand(10)
    if False:  # speed
        model_out = model(inputs)
        pipe_out = pipe(inputs)

        torch.distributed.barrier()

        if pipe.final_stage:
            assert torch.equal(model_out, pipe_out)

    model.train()
    pipe.train()
    model_out = model(inputs)
    pipe_out = pipe(inputs)
    if pipe.final_stage:
        pipe_loss = pipe_out.mean()
        pipe_loss.backward()

    model_loss = model_out.mean()
    model_loss.backward()

    model_optimizer.step()
    if pipe_optimizer:
        pipe_optimizer.step()

    model.eval()
    pipe.eval()
    model_out = model(inputs)
    pipe_out = pipe(inputs)

    print(f"before barrier on {torch.distributed.get_rank()}")
    torch.distributed.barrier()
    print(f"after barrier on {torch.distributed.get_rank()}")

    if pipe.final_stage:
        assert torch.equal(model_out, pipe_out)


def test_instantiate_partition():
    from fairscale.nn.pipe.async_schedule import Location
    from fairscale.nn.pipe.pipe import instantiate_partition

    class FakeGroup:
        def __init__(self, rank, size):
            self._rank = rank
            self._size = size

        def rank(self):
            return self._rank

        def size(self):
            return self._size

    def check_partitions(model, balance, expected_order, expected_ranks):
        """Check the instantiated model matches expectation of order and rank

        model: a list of modules or an nn.Sequential
        balance: the balance argument to Pipe
        expected_order: the index of modules in `model` in the order they will
            be executed, grouped by nn.Sequential
        expected_rank: the rank that each module will be executed on
        """

        invocations = []
        invocation_wrapper = dict()

        # Collect `Invocation` and `Invocation` -> `ModuleWrapper` mapping from
        # instantiated model
        for rank in range(len(balance)):
            instantiated = instantiate_partition(model, balance, FakeGroup(rank, len(balance)), Pipe.AsyncSchedule)
            for part in instantiated:
                assert isinstance(part.module, nn.Sequential)
                for inv in part.invocations:
                    invocations.append(inv)
                    invocation_wrapper[inv] = part

        modules = []
        prev = None
        current = Location(0, 0)
        ranks = []

        for order, inv in enumerate(sorted(invocations, key=lambda x: x.order)):
            # Check integrity of Location chain
            assert inv.order == order
            assert inv.source == prev
            assert inv.this == current
            prev = inv.this
            current = inv.dest
            modules.append(list(invocation_wrapper[inv].module.children()))
            ranks.append(inv.this.stage)

        # assert len(modules) == len(expected_order)
        for left, right in zip(modules, expected_order):
            assert len(left) == len(right), f"{right}"
            assert list(map(id, left)) == list(map(id, (model[e] for e in right))), f"{right}"

        assert ranks == expected_ranks

    reused = nn.Linear(20, 20)
    model = [reused, nn.Linear(10, 10), nn.ReLU(), reused, nn.ReLU(), reused, nn.ReLU()]
    balance = [3, 1, 1]

    check_partitions(
        model, balance, expected_order=[[0], [1, 2], [0], [4], [0], [6]], expected_ranks=[0, 0, 0, 1, 0, 2]
    )

    reused2 = nn.Linear(5, 5)
    model = [reused, reused2, nn.Linear(10, 10), nn.ReLU(), reused, reused2, nn.ReLU(), reused, reused2, nn.ReLU()]
    balance = [4, 1, 1]

    check_partitions(
        model,
        balance,
        expected_order=[[0], [1], [2, 3], [0], [1], [6], [0], [1], [9]],
        expected_ranks=[0, 0, 0, 0, 0, 1, 0, 0, 2],
    )

    reused2 = nn.Linear(5, 5)
    model = [
        nn.Linear(10, 10),
        reused,
        nn.Linear(10, 10),
        nn.ReLU(),
        reused,
        reused2,
        nn.ReLU(),
        reused,
        reused2,
        nn.ReLU(),
    ]
    # 0 1 2 3 1 5 6 1 5 9
    balance = [4, 2, 1]

    check_partitions(
        model,
        balance,
        expected_order=[[0], [1], [2, 3], [1], [5], [6], [1], [5], [9]],
        expected_ranks=[0, 0, 0, 0, 1, 1, 0, 1, 2],
    )