python/tvm/auto_scheduler/compute_dag.py

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""" The auto-scheduler's computational graph and related program analyses. """

import hashlib

import tvm._ffi
from tvm.runtime import Object
from tvm.te import PlaceholderOp, ComputeOp

from .loop_state import State, StateObject
from .utils import get_const_tuple
from .workload_registry import workload_key_to_tensors

from . import _ffi_api


@tvm._ffi.register_object("auto_scheduler.ComputeDAG")
class ComputeDAG(Object):
    """
    The auto-scheduler's computational graph and related program analyses.

    We convert a compute declaration described by `tvm.compute` (could be a single operator or a
    subgraph) to a ComputeDAG. It keeps the input/output tensors, all operations in the DAG, and
    some static analysis results for the DAG (e.g. the total float operation count,
    consumer/producer relations of operations, whether an operation stage should
    be tiled/compute inlined).
    These analyses can help the search policy to make decisions during the search.
    ComputeDAG is also responsible for the interaction between auto-scheduler's `LoopState` and
    TVM schedule (e.g. applying the `LoopState` transform steps to a TVM schedule, providing
    `LoopState` with extra information got from TVM schedule).

    Parameters
    ----------
    compute : Union[List[Tensor], str]
        Input/output tensors or workload key for a compute declaration.
    """

    def __init__(self, compute):
        if isinstance(compute, str):
            compute = workload_key_to_tensors(compute)
        elif isinstance(compute, list):
            for item in compute:
                if not isinstance(item, tvm.te.Tensor):
                    raise ValueError("The input of ComputeDAG should be a list of Tensor")
        else:
            raise ValueError(
                "Invalid compute: " + compute + " . ComputeDAG expects a string or list of Tensor"
            )
        self.__init_handle_by_constructor__(_ffi_api.ComputeDAG, compute)

    def get_init_state(self):
        """Get the init state of this ComputeDAG.

        Returns
        -------
        state : State
            The initial State without any transform steps.
        """
        return State(self.init_state, self)

    def apply_steps_from_state(self, state, layout_rewrite=False):
        """
        Apply the history transform steps from a State to get a TVM schedule.

        Parameters
        ----------
        state : Union[State, StateObject]
            The state from which we get transform steps.

        layout_rewrite: Bool
            Rewrite the layout of placeholders specified by "layout_free_placeholders" attr
            to make it most friendly for the generated schedule to read from.

        Returns
        -------
            A `te.schedule` and the a list of `te.Tensor` to be used in `tvm.lower` or `tvm.build`.
        """
        state_obj = state if isinstance(state, StateObject) else state.state_object
        return _ffi_api.ComputeDAGApplyStepsFromState(self, state_obj, layout_rewrite)

    def print_python_code_from_state(self, state):
        """
        Print transform steps in the history of a State as TVM's python schedule code.

        This is used to print transformation steps for debugging.
        Use `apply_steps_from_state` if you want to get a schedule for code generation.

        Parameters
        ----------
        state : Union[State, StateObject]
            The state from which we get transform steps.

        Returns
        -------
        str : Str
            The Python schedule code.
        """
        state_obj = state if isinstance(state, StateObject) else state.state_object
        return _ffi_api.ComputeDAGPrintPythonCodeFromState(self, state_obj)

    def infer_bound_from_state(self, state):
        """
        Infer and fill the bound of all iterators of a state.

        The states may lose complete bound information after some transform steps
        (e.g., compute_at).
        We can call this function to infer and fill all the bound information.
        This function calls TVM InferBound pass internally to get the bound.
        The returned state of this function is guaranteed to have complete iterator extent
        information.

        Parameters
        ----------
        state : Union[State, StateObject]
            The state from which we get transform steps.

        Returns
        -------
        updated_state : State
            The State with complete bound information.
        """
        state_obj = state if isinstance(state, StateObject) else state.state_object
        updated_state = State(_ffi_api.ComputeDAGInferBoundFromState(self, state_obj), self)
        # Copy the stage_id_map from the original state to make sure the old indices are still
        # valid
        if isinstance(state, State):
            for k, v in state.stage_id_map.items():
                updated_state.stage_id_map[k] = v
        return updated_state

    def __hash__(self):
        # TODO(merrymercy): Implement this more carefully and move this to c++ as a member function
        # of ComputeDAG
        str_key = ""
        for op in self.ops:
            t = op.output(0)
            if isinstance(op, PlaceholderOp):
                str_key += "placeholder,"
                str_key += str(get_const_tuple(t.shape)) + ","
                str_key += t.dtype + ";"
            elif isinstance(op, ComputeOp):
                str_key += str(t.op.body) + ","
                str_key += str(get_const_tuple(t.shape)) + ","
                str_key += t.dtype + ";"
            else:
                raise ValueError("Invalid op: " + op)

        str_key = str_key.encode(encoding="utf-8")
        return hashlib.md5(str_key).hexdigest()