tkonolige commented on a change in pull request #7083: URL: https://github.com/apache/tvm/pull/7083#discussion_r554178005
########## File path: python/tvm/relay/op/random/kernel.py ########## @@ -0,0 +1,134 @@ +# 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. +"""Splittable and parallelizable PRNG kernels.""" +# pylint: disable=invalid-name,unused-argument +from __future__ import absolute_import + +import sys +import numpy as np + +from ...expr import Constant +from .... import nd +from . import _make + + +def threefry_key(seed): + """Create a new Threefry random number generator key. + + Example + ------- + + .. code-block:: python + + gen = threefry_key(0) + _, random_number = threefry_generate(gen, (4,)) + + Parameters + ---------- + seed : int + Starting seed for the key + + Returns + ------- + key : relay.Expr + New key to pass to future uses of :py:func:`threefry_split` or + :py:func:`threefry_generate`. + """ + s = np.frombuffer(seed.to_bytes(32, sys.byteorder), dtype="uint64") + a = np.concatenate((s, np.array([0, 0, 0, 0, 1 << 63, 0], dtype="uint64"))) + return Constant(nd.array(a)) + + +def threefry_generate(key, shape): + """Generate an array of random bits (`uint64`) using the Threefry algorithm + + Example + ------- + + .. code-block:: python + + key = threefry_key(0) + new_key, random1 = threefry_generate(key, (4,)) + _, random2 = threefry_generate(new_key, (4,)) + # random1 and random2 are different random numbers + + Parameters + ---------- + key : relay.Expr + key that uniquely determines the random values. Multiple uses with the + same key will generate the same random values. This key should be + treated as an opaque pointer. You can create one from calling + :py:func:`threefry_key`, :py:func:`threefry_split`, or + :py:func:`threefry_generate`. **Do not use this key again after calling + this function.** + + shape : Sequence[int] + Desired outputs shape of random numbers. **Currently the total + number of elements must be a multiple of 4.** + + Returns + ------- + new_key : relay.Expr + New key to pass to future uses of :py:func:`threefry_split` or + :py:func:`threefry_generate`. + + random_array : relay.Expr + Array of random numbers. Has shape `shape`. + """ + return _make.threefry_generate(key, shape) + + +def threefry_split(key): + """Split an existing Threefry key into two new ones. + + This is useful if you have to subsequent calls which each need their own Review comment: Creating separate keys has not been theoretically proven to be as random as splitting a single key. Maybe I should add a comment that you should only really create one key. On the other hand, these details might be better handled at a higher level interface (future work). ---------------------------------------------------------------- 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. For queries about this service, please contact Infrastructure at: [email protected]
