masahi commented on code in PR #14446: URL: https://github.com/apache/tvm/pull/14446#discussion_r1154854436
########## python/tvm/relax/dpl/rewrite.py: ########## @@ -0,0 +1,115 @@ +# Licensed to the Apache Software Foundation (ASF) under one +# or more contributor license agreements. See the NOTICE file +# distributed with this work for additional information +# regarding copyright ownership. The ASF licenses this file +# to you 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. +"""APIs for pattern-based rewriting.""" +from typing import Dict, Callable +from .pattern import DFPattern +from .context import PatternContext + +from ..expr import Expr, Function, Var +from . import _ffi as ffi + + +def rewrite_call( + pattern: DFPattern, rewriter: Callable[[Expr, Dict[DFPattern, Expr]], Expr], func: Function +) -> Function: + """ + Rewrite a function with the given pattern and the rewriter function. + + Parameters + ---------- + pattern: DFPattern + The pattern to match. + + rewriter: Callable[[Expr, Dict[DFPattern, Expr]], Expr] + The function to be called on a successful matching for rewriting. Given the matched + call node and the map of patterns and matched expressions, it should return a new call node + to replace the original one or the original matched call node as is. + + For example, to replace x + x with 2 * x, we can write the rewriter as follows: + ``` + x = wildcard() + pattern = is_op("relax.add")(x, x) + + def rewriter(orig, matchings): + return R.multiply(matchings[x], R.const(2, "float32")) + ``` + + func: Function + The function to rewrite. + + Returns + ------- + rewritten_func: Function + The rewritten or the input function, depending on the pattern matching result. + """ + return ffi.rewrite_call(pattern, rewriter, func) + + +def rewrite_bindings( + ctx: PatternContext, rewriter: Callable[[Dict[DFPattern, Var]], Dict[Var, Expr]], func: Function +) -> Function: + """ + Rewrite a function with the given pattern and the rewriter function. + + Parameters + ---------- + ctx: PatternContext + The pattern constraint context under which rewriting takes place. + + rewriter: Callable[[Dict[DFPattern, Var]], Dict[Var, Expr]] + The function to be called on a successful matching for rewriting. Given the map of patterns + and corresponding variables (bound variables or parameters), it should return a map that + specifies new values for matched bound variables. + + For example, to rewrite three matmuls for QKV projection in transformer models into one + matmul followed by slicing, one can use the follwoing rewriter: + ``` + inp_pat = wildcard() + Q_weight_pat, K_weight_pat, V_weight_pat = wildcard(), wildcard(), wildcard() + + matmul1 = is_op("relax.matmul")(inp_pat, Q_weight_pat) + matmul2 = is_op("relax.matmul")(inp_pat, K_weight_pat) + matmul3 = is_op("relax.matmul")(inp_pat, V_weight_pat) + + def rewriter(matchings): + inp = matchings[inp_pat] + Q_weight = matchings[Q_weight_pat] + K_weight = matchings[K_weight_pat] + V_weight = matchings[V_weight_pat] + width = Q_weight.struct_info.shape[1] + + concat = R.concat([Q_weight, K_weight, V_weight], axis=1) + matmul = R.matmul(inp, concat) + Q = R.strided_slice(matmul, axes=[2], begin=[0], end=[width]) + K = R.strided_slice(matmul, axes=[2], begin=[width], end=[width * 2]) + V = R.strided_slice(matmul, axes=[2], begin=[width * 2], end=[width * 3]) + + # matchings[matmul1] gives the bound variable in the binding whose RHS matches with + # the matmul1 pattern. For example, lv0 in lv0 = R.matmul(x1, w0). + # We want to replace the RHS of this binding with Q. + return {matchings[matmul1]: Q, matchings[matmul2]: K, matchings[matmul3]: V} + ``` Review Comment: I hope the API for the rewriter makes sense and the usage is intuitive. It took me a while to workout this interface together with how the rewriting mutator should be implemented in `dataflow_matcher.cc`. cc @ganler -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
