pytorch/torch/_dynamo/variables/tensor.py

import copy
import functools
import itertools
import math
import numbers
import operator
from typing import Dict, List

import torch.fx
import torch.random

from ..utils import fake_tensors_available

if fake_tensors_available:
    from torch._subclasses import FakeTensor
    from torch._subclasses.fake_tensor import (
        DataDependentOutputException,
        DynamicOutputShapeException,
    )
    from ..utils import deepcopy_to_fake_tensor, wrap_to_fake_tensor_and_record

import torch.utils._python_dispatch as py_dispatch
from torch.fx.immutable_collections import immutable_list
from torch.utils._pytree import tree_map

from .. import config, variables
from ..exc import TorchRuntimeError, unimplemented, Unsupported
from ..guards import GuardBuilder
from ..source import AttrSource
from ..utils import (
    clone_input,
    is_lazy_module,
    istype,
    preserve_rng_state,
    product,
    proxy_args_kwargs,
    tensortype_to_dtype,
)
from .base import MutableLocal, typestr, VariableTracker
from .constant import ConstantVariable
from .lists import ShapeVariable, SizeVariable


class _missing:
    pass


def _run_node(output_graph, node, args, kwargs, nnmodule):
    op = node.op
    if op == "call_function":
        return node.target(*args, **kwargs)
    elif op == "call_method":
        return getattr(args[0], node.target)(*args[1:], **kwargs)
    elif op == "call_module":
        assert nnmodule is not None
        return nnmodule(*args, **kwargs)
    elif op == "get_attr":
        return output_graph.get_submodule(node.target)
    raise AssertionError(op)


def _get_real_value(node, output_graph):
    """
    Run the actual computation represented by `node` and return the result.
    This will execute any dependent nodes in the graph as well.
    """
    cache = output_graph.real_value_cache
    if node in cache:
        return cache[node]

    op = node.op
    args, kwargs = torch.fx.node.map_arg(
        (node.args, node.kwargs),
        lambda n: _get_real_value(n, output_graph),
    )

    if op == "call_module":
        nn_module = output_graph.nn_modules[node.target]
        if not is_lazy_module(nn_module):
            nn_module = copy.deepcopy(nn_module)
        else:
            # In the case of a lazy module, we want to run
            # the pre-hooks which initialize it
            nn_module(*args, **kwargs)
    else:
        nn_module = None

    try:
        real_value = _run_node(output_graph, node, args, kwargs, nn_module)
        cache[node] = real_value
    except RuntimeError as e:
        raise TorchRuntimeError() from e
    return real_value


def _get_fake_value(node, tx):
    """
    Run the computation represented by `node` using fake tensors and return the result.
    """
    op = node.op
    fake_wrapper = functools.partial(wrap_to_fake_tensor_and_record, tx=tx)
    from ..utils import wrap_fake_exception

    def visit(n: torch.fx.Node):
        return n.meta["example_value"]

    args, kwargs = torch.fx.node.map_arg((node.args, node.kwargs), visit)
    args = tree_map(fake_wrapper, args)
    kwargs = tree_map(fake_wrapper, kwargs)

    nnmodule = None
    if op == "call_module":
        nnmodule = tx.output.nn_modules[node.target]

        if not is_lazy_module(nnmodule):
            nnmodule = deepcopy_to_fake_tensor(nnmodule, tx.fake_mode)

    def context():
        if hasattr(py_dispatch, "enable_torch_dispatch_mode"):
            return py_dispatch.enable_torch_dispatch_mode(tx.fake_mode)
        else:
            return tx.fake_mode

    if op == "call_module" and is_lazy_module(nnmodule):
        assert nnmodule is not None
        # In the case of a lazy module, we want to run
        # the pre-hooks which initialize it
        nnmodule(*args, **kwargs)
    try:
        with context():
            return wrap_fake_exception(
                lambda: _run_node(tx.output, node, args, kwargs, nnmodule)
            )
    except Unsupported:
        raise
    except RuntimeError as e:
        if isinstance(e, DataDependentOutputException):
            if config.capture_scalar_outputs and node.target == "item":
                return torch.zeros(size=(), dtype=args[0].dtype).item()
            else:
                unimplemented(f"data dependent operator: {e.func}")
        elif isinstance(e, DynamicOutputShapeException):
            unimplemented(f"dynamic shape operator: {e.func}")
        else:
            raise TorchRuntimeError() from e


def _clone_input(value):
    if isinstance(value, torch.Tensor):
        use_fake_tensors = fake_tensors_available and config.fake_tensor_propagation
        # tensor subclasses will not be converted to FakeTensors and need to be cloned
        if not use_fake_tensors or not isinstance(value, FakeTensor):
            # NB: ensure strides are preserved
            value = clone_input(value)

    return value


class TensorVariable(VariableTracker):
    """A torch.Tensor input or an intermediate value in the FX graph"""

    _nonvar_fields = [
        "proxy",
        "dtype",
        "device",
        "ndim",
        "size",
        "stride",
        "requires_grad",
        "is_quantized",
        "is_contiguous",
    ]

    def get_real_value(self):
        """
        Get the actual value represented by this variable if computation is run
        using the user-provided inputs.
        NOTE: this runs actual tensor computation and may be
        slow and memory-intensive.
        """
        return _get_real_value(self.proxy.node, self.proxy.tracer)

    @classmethod
    def create(cls, tx, proxy, example_value=None, **options):
        if "guards" in options and options["guards"] is not None:
            tx.output.guards.update(options["guards"])

        assert "example_value" not in proxy.node.meta
        if not config.dynamic_propagation:
            if isinstance(example_value, torch.Tensor):
                options.update(cls.specialize(example_value))
            return cls(proxy, **options)

        use_fake_tensors = fake_tensors_available and config.fake_tensor_propagation

        initial_example_value = example_value

        with preserve_rng_state():
            if example_value is None:
                if use_fake_tensors:
                    example_value = _get_fake_value(proxy.node, tx)
                else:
                    example_value = _get_real_value(proxy.node, tx.output)

            else:
                proxy.tracer.real_value_cache[proxy.node] = _clone_input(example_value)
                if use_fake_tensors:
                    fake_wrapper = functools.partial(
                        wrap_to_fake_tensor_and_record, tx=tx
                    )
                    example_value = fake_wrapper(example_value)

        if isinstance(example_value, torch.Tensor):
            is_parameter = isinstance(example_value, torch.nn.Parameter)
            should_specialize = options.pop("should_specialize", False)
            if is_parameter or should_specialize:
                specialized_value = initial_example_value
            else:
                specialized_value = None

            example_value = _clone_input(example_value)
            proxy.node.meta["example_value"] = example_value
            specialized_props = cls.specialize(example_value)
            if use_fake_tensors and isinstance(example_value, FakeTensor):
                specialized_props["class_type"] = (
                    torch.nn.Parameter if is_parameter else torch.Tensor
                )

            specialized_props["specialized_value"] = specialized_value

            options.update(specialized_props)
            return cls(proxy, **options)
        elif (
            hasattr(proxy.node.target, "__name__")
            and proxy.node.target.__name__ == "set_state"
            and isinstance(proxy.node.target.__self__, torch._C.Generator)
            or proxy.node.target == torch.random.set_rng_state
        ):
            from . import TorchVariable

            return TorchVariable(proxy.node.target)
        elif istype(example_value, (int, bool, float)) and config.dynamic_shapes:
            proxy.node.meta["example_value"] = example_value
            return DynamicShapeVariable(proxy, example_value, **options)
        elif istype(example_value, torch.Size) and config.dynamic_shapes:
            proxy.node.meta["example_value"] = example_value
            sizes = []
            for i, v in enumerate(example_value):
                proxy_i = proxy[i]
                proxy_i.node.meta["example_value"] = v
                sizes.append(DynamicShapeVariable(proxy_i, v))
            return SizeVariable(sizes, proxy, **options)
        elif istype(example_value, int) and proxy.node.target in (
            torch.seed,
            operator.mod,
            # some mac builds are missing torch.distributed.get_rank()
            getattr(torch.distributed, "get_rank", _missing),
            getattr(torch.distributed, "get_world_size", _missing),
        ):
            proxy.node.meta["example_value"] = example_value
            return DynamicShapeVariable(proxy, example_value, **options)
        elif istype(example_value, torch.Size) and all(
            [isinstance(x, int) for x in example_value]
        ):
            sizes = [variables.ConstantVariable(x) for x in example_value]
            return SizeVariable(sizes, **options)
        elif isinstance(example_value, (tuple, list)):
            unpacked = []
            for i, val in enumerate(example_value):
                if val is None:
                    # nn.MultiheadAttention() can return None, see issue #175
                    unpacked.append(
                        variables.ConstantVariable(None, **options),
                    )
                else:
                    unpacked.append(
                        cls.create(
                            tx,
                            proxy.tracer.create_proxy(
                                "call_function", operator.getitem, (proxy, i), {}
                            ),
                            example_value=val,
                            **options,
                        )
                    )
            if istype(example_value, tuple):
                return variables.TupleVariable(unpacked, **options)
            elif istype(example_value, (list, immutable_list)):
                return variables.ListVariable(
                    unpacked, mutable_local=MutableLocal(), **options
                )
            else:
                assert (
                    example_value.__class__.__module__ == "torch.return_types"
                    or hasattr(example_value, "_fields")
                ), "namedtuple?"
                return variables.NamedTupleVariable(
                    unpacked, example_value.__class__, **options
                )
        elif example_value is None or proxy.node.target is torch.manual_seed:
            return variables.ConstantVariable(None, **options)
        elif (
            isinstance(example_value, int)
            and proxy.node.target is torch._utils._element_size
        ):
            proxy.node.meta["example_value"] = example_value
            return variables.ConstantVariable(example_value, **options)
        elif (
            isinstance(example_value, numbers.Number)
            and (
                proxy.node.target == "item"
                or proxy.node.target in {math.sqrt, math.pow}
            )
            and config.capture_scalar_outputs
        ):
            if use_fake_tensors:
                # item raw value should not be accessed
                return FakeItemVariable.create(
                    tx=tx,
                    proxy=proxy,
                    example_value=torch.tensor(example_value),
                    **options,
                )
            else:
                return UnspecializedPythonVariable.create(
                    tx=tx,
                    proxy=proxy,
                    example_value=torch.tensor(example_value),
                    raw_value=None if use_fake_tensors else example_value,
                    need_unwrap=False,
                    **options,
                )
        elif (
            proxy.node.target == torch._C._DisableFuncTorch
            or proxy.node.target == torch.cuda._is_in_bad_fork
        ):
            from . import UserDefinedObjectVariable

            return UserDefinedObjectVariable(example_value)
        elif isinstance(example_value, torch.SymIntNode):
            proxy.node.meta["example_value"] = example_value
            return cls(proxy, **options)
        else:
            raise AssertionError(
                "torch.* op returned non-Tensor "
                + f"{typestr(example_value)} {proxy.node.op} {proxy.node.target}"
            )

    def __init__(
        self,
        proxy: torch.fx.Proxy,
        dtype=None,
        device=None,
        ndim=None,
        size=None,
        stride=None,
        requires_grad=None,
        is_quantized=None,
        is_contiguous=None,
        is_sparse=None,
        class_type=torch.Tensor,
        specialized_value=None,
        **kwargs,
    ):
        super(TensorVariable, self).__init__(**kwargs)
        self.proxy = proxy
        self.dtype = dtype
        self.device = device
        self.ndim = ndim
        self.size = size
        self.stride = stride
        self.requires_grad = requires_grad
        self.is_quantized = is_quantized
        self.is_contiguous = is_contiguous
        self.is_sparse = is_sparse
        self.class_type = class_type
        self.specialized_value = specialized_value

    def as_proxy(self):
        return self.proxy

    def python_type(self):
        return self.class_type

    def call_isinstance(self, tensor_type):
        def check_type(ty):
            if ty not in tensortype_to_dtype:
                return issubclass(self.python_type(), ty)

            dtypes = tensortype_to_dtype[ty]
            return self.dtype in dtypes

        if type(tensor_type) is tuple:
            return any([check_type(ty) for ty in tensor_type])
        else:
            return check_type(tensor_type)

    @staticmethod
    def specialize(value: torch.Tensor):
        props = {
            "dtype": value.dtype,
            "device": value.device,
            "ndim": int(value.ndim),
            "requires_grad": value.requires_grad,
            "is_quantized": value.is_quantized,
            "is_sparse": value.is_sparse,
            "class_type": type(value),
        }
        if not config.dynamic_shapes:
            props["size"] = tuple(value.size())
            props["stride"] = tuple(value.stride())
            props["is_contiguous"] = value.is_contiguous()
        return props

    def var_getattr(self, tx, name):
        from . import ConstantVariable, TorchVariable

        result = None
        options = VariableTracker.propagate(self)
        if name == "ndim" and self.ndim is not None:
            result = ConstantVariable(self.ndim, **options)
        elif name == "dtype" and self.dtype is not None:
            result = TorchVariable(self.dtype, **options)
        elif name == "device" and self.device is not None:
            result = TorchVariable(self.device, **options)
        elif name == "is_cuda" and self.device is not None:
            result = ConstantVariable(self.device.type == "cuda", **options)
        elif name == "shape" and self.size is not None:
            sizes = [variables.ConstantVariable(x) for x in self.size]
            result = ShapeVariable(sizes, **options)
        elif name == "requires_grad" and self.requires_grad is not None:
            result = ConstantVariable(self.requires_grad, **options)
        elif name == "is_quantized" and self.is_quantized is not None:
            result = ConstantVariable(self.is_quantized, **options)
        elif name == "is_sparse" and self.is_sparse is not None:
            result = ConstantVariable(self.is_sparse, **options)
        elif name == "shape" and self.size is None:
            result = self.call_method(tx, "size", [], {})
        elif name == "ndim" and self.ndim is None:
            result = self.call_method(tx, "dim", [], {})

        if name == "__class__":
            return TorchVariable(self.python_type(), **options)

        # Add a guard for type matching, these guards are checked before tensor guards
        # In some cases, a <tensor>.<attr> guard can be evaluated first, and break if
        # <tensor> is later changed to another type
        if result is not None and self.source is not None:
            result = result.add_guard(self.make_guard(GuardBuilder.TYPE_MATCH))

        if result is None:
            raise NotImplementedError()

        return result

    def unpack_var_sequence(self, tx):
        options = VariableTracker.propagate(self)
        if self.size:
            return [
                variables.BuiltinVariable(operator.getitem, **options).call_function(
                    tx, [self, variables.ConstantVariable(i)], {}
                )
                for i in range(self.size[0])
            ]

        return super(TensorVariable, self).unpack_var_sequence(tx)

    def call_method(
        self,
        tx,
        name,
        args: "List[VariableTracker]",
        kwargs: "Dict[str, VariableTracker]",
    ) -> "VariableTracker":
        from . import ConstantVariable, TupleVariable

        kwargs = dict(kwargs)

        options = VariableTracker.propagate(self, args, kwargs.values())
        if name == "stride" and self.stride is not None:
            constant_result = ConstantVariable(self.stride, **options)
        elif name == "size" and self.size is not None:
            sizes = [variables.ConstantVariable(x) for x in self.size]
            constant_result = SizeVariable(sizes, **options)
        elif name == "numel" and self.size is not None:
            constant_result = ConstantVariable(product(self.size), **options)
        elif name in ("ndimension", "dim") and self.ndim is not None:
            constant_result = ConstantVariable(self.ndim, **options)
        elif name == "is_floating_point" and self.dtype is not None:
            constant_result = ConstantVariable(self.dtype.is_floating_point, **options)
        elif name == "is_contiguous" and self.is_contiguous is not None:
            if (
                "memory_format" in kwargs
                and kwargs["memory_format"].as_python_constant()
                == torch.contiguous_format
            ):
                kwargs.pop("memory_format")
            constant_result = ConstantVariable(self.is_contiguous, **options)
        else:
            constant_result = None

        if constant_result:
            assert not kwargs, f"Tensor.{name}() unhandled kwargs"
            if len(args) == 1:
                return constant_result.getitem_const(args[0])
            elif args:
                return TupleVariable(
                    [constant_result.getitem_const(a) for a in args], **options
                )
            return constant_result
        elif (
            name == "repeat"
            and not all(
                x.is_python_constant() for x in itertools.chain(args, kwargs.values())
            )
            and not config.dynamic_shapes
        ):
            unimplemented("dynamic Tensor.repeat")
        elif name in ("tolist", "numpy", "backward"):
            unimplemented(f"Tensor.{name}")
        elif name == "nonzero" and not config.dynamic_shapes:
            unimplemented(f"Tensor.{name}")
        elif name == "item":
            if config.capture_scalar_outputs:
                return self.__class__.create(
                    tx,
                    tx.output.create_proxy(
                        "call_method", "item", (self.as_proxy(),), {}, current_tx=tx
                    ),
                    **options,
                )
            else:
                unimplemented(f"Tensor.{name}")
        elif name == "__len__":
            if self.size:
                assert not config.dynamic_shapes
                return ConstantVariable(self.size[0], **options)
            else:
                return self.__class__.create(
                    tx,
                    tx.output.create_proxy(
                        "call_function", len, (self.as_proxy(),), {}, current_tx=tx
                    ),
                    **options,
                )
        elif name == "__setitem__":
            tx.output.guards.update(options["guards"])
            tx.output.create_proxy(
                "call_function",
                operator.setitem,
                *proxy_args_kwargs([self] + args, kwargs),
                current_tx=tx,
            )
            return ConstantVariable(None, **options)
        else:
            # Convert x.new(torch.Size) into x.new_empty(torch.Size),
            # as Tensor.new acts differently with a Size input versus a tuple input.
            if (
                name == "new"
                and len(args) == 1
                and isinstance(args[0], (SizeVariable, ShapeVariable))
                and not config.dynamic_shapes
            ):
                name = "new_empty"

            return self.__class__.create(
                tx,
                tx.output.create_proxy(
                    "call_method",
                    name,
                    *proxy_args_kwargs([self] + args, kwargs),
                    current_tx=tx,
                ),
                **options,
            )


class DynamicShapeVariable(TensorVariable):
    """
    Represents a symbolic size, e.g., as returned by tensor.size(0)
    """

    def __init__(self, proxy, dyn_shape, **kwargs):
        super(DynamicShapeVariable, self).__init__(proxy, **kwargs)
        self.dyn_shape = dyn_shape

    def python_type(self):
        return type(self.dyn_shape)

    def unpack_var_sequence(self, tx):
        super(DynamicShapeVariable, self).unpack_var_sequence(tx)


class TensorWithTFOverrideVariable(VariableTracker):
    """
    Represents a tensor subclass instance with a __torch_function__ override.
    """

    def __init__(
        self,
        tensor_variable,
        orig_tensor_variable_source,
        subclass_torch_function__func,
        subclass_type,
        **kwargs,
    ):
        super(TensorWithTFOverrideVariable, self).__init__(**kwargs)
        self.tensor_variable = tensor_variable
        self.orig_tensor_variable_source = orig_tensor_variable_source
        self.subclass_torch_function__func = subclass_torch_function__func
        self.subclass_type = subclass_type

    def call_method(
        self,
        tx,
        name,
        args: "List[VariableTracker]",
        kwargs: "Dict[str, VariableTracker]",
    ) -> "VariableTracker":
        # This code block implements inlining the __torch_function__ override
        # of `call_method`.
        from . import GetAttrVariable

        options = VariableTracker.propagate(self, args, kwargs.values())
        # insert unwrapped version of self as the first argument
        args = list(args)
        args.insert(0, self.tensor_variable)
        func_var = GetAttrVariable(self.tensor_variable, name)

        unwrapped = TensorWithTFOverrideVariable.inline_torch_function_unwrapped(
            tx,
            func_var,
            self.orig_tensor_variable_source,
            self.subclass_torch_function__func,
            self.subclass_type,
            options,
            args,
            kwargs,
        )

        # TODO(future PR): implement rewrapping conditional on method presence
        # in `torch.overrides.get_default_nowrap_function()`. It's unclear how
        # to do this easily in the current codebase since the resolution of
        # `GetAttrVariable` depends on the type of the underlying object.

        return TensorWithTFOverrideVariable(
            unwrapped,
            self.orig_tensor_variable_source,
            self.subclass_torch_function__func,
            self.subclass_type,
        )

    @staticmethod
    def inline_torch_function_unwrapped(
        tx,
        original_func_var,
        tensor_with_tf_override_source,
        tf_func,
        subclass_type,
        options,
        args,
        kwargs,
    ):
        """
        This function inlines the `__torch_function__` override for `original_func_var`.
        For example, if the user code is

           x1 = torch.sigmoid(x0)

        And `x0` has an override, then:
        * `original_func_var` will be a `VariableTracker` object wrapping `torch.sigmoid`
        * `tensor_with_tf_override_source` will be the `Source` object from
          the original tensor override instance in the beginning of the program
        * `tf_func` will be the custom `__torch_function__` function
        * `subclass_type` will be `type(x0)`

        The caller is expected to properly massage args and kwargs before
        passing them into this function.

        The caller is responsible for wrapping the return value, if needed.
        """
        from . import UserDefinedClassVariable
        from .builder import TupleVariable, VariableBuilder

        source = AttrSource(
            AttrSource(tensor_with_tf_override_source, "__torch_function__"),
            "__func__",
        )
        tf_func_var = VariableBuilder(tx, source)(tf_func)
        type_var = UserDefinedClassVariable(subclass_type, **options)

        # signature:
        # def __torch_function__(cls, func, types, args=(), kwargs=None):
        tf_args = (
            type_var,  # cls
            original_func_var,  # func
            (type_var,),  # types
            TupleVariable(args),  # args
            kwargs,  # kwargs
        )

        # Disable __torch_function__ here to prevent the clone of the
        # example tensor from going into the override.
        with torch._C.DisableTorchFunction():
            return tx.inline_user_function_return(tf_func_var, tf_args, {})


class UnspecializedNumpyVariable(TensorVariable):
    """
    This is a 1-element tensor represents unspecialized numpy float/int.
    """

    def __init__(self, proxy: torch.fx.Proxy, **kwargs):
        raw_value = kwargs.pop("raw_value", None)
        super(UnspecializedNumpyVariable, self).__init__(proxy, **kwargs)
        self.raw_value = raw_value

    @classmethod
    def from_tensor_variable(cls, tensor_variable, raw_value):
        # Convert a `TensorVariable` instance into an `UnspecializedNumpyVariable` instance.
        return UnspecializedNumpyVariable(
            **dict(tensor_variable.__dict__), raw_value=raw_value
        )

    def as_specialized(self, tx):
        for graph_arg in tx.output.graphargs:
            if graph_arg.source is self.source:
                graph_arg.erase()

        for g in self.guards:
            if g.is_volatile:
                g.create_fn = GuardBuilder.CONSTANT_MATCH

        return ConstantVariable(value=self.raw_value, guards=self.guards)


class UnspecializedPythonVariable(TensorVariable):
    """
    This is a 1-element tensor represents unspecialized python float/int.
    """

    def __init__(self, proxy: torch.fx.Proxy, **kwargs):
        raw_value = kwargs.pop("raw_value", None)
        need_unwrap = kwargs.pop("need_unwrap", True)
        super(UnspecializedPythonVariable, self).__init__(proxy, **kwargs)
        self.raw_value = raw_value
        self.need_unwrap = need_unwrap

    @classmethod
    def from_tensor_variable(cls, tensor_variable, raw_value, need_unwrap=True):
        # Convert a `TensorVariable` instance into an `UnspecializedPythonVariable` instance.
        return UnspecializedPythonVariable(
            **dict(tensor_variable.__dict__),
            raw_value=raw_value,
            need_unwrap=need_unwrap,
        )

    def as_specialized(self, tx):
        for graph_arg in tx.output.graphargs:
            if graph_arg.source is self.source:
                graph_arg.erase()

        for g in self.guards:
            if g.is_volatile:
                g.create_fn = GuardBuilder.CONSTANT_MATCH

        return ConstantVariable(value=self.raw_value, guards=self.guards)


class FakeItemVariable(TensorVariable):
    """An unspecialized python variable which prevents access to the underlying raw value.
    This is needed if item is called on a FakeTensor."""

    def __init__(self, proxy: torch.fx.Proxy, **kwargs):
        need_unwrap = kwargs.pop("need_unwrap", False)
        super(FakeItemVariable, self).__init__(proxy, **kwargs)
        self.need_unwrap = need_unwrap

    @classmethod
    def from_tensor_variable(cls, tensor_variable):
        return FakeItemVariable(**dict(tensor_variable.__dict__))