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multinomial.ts
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/**
* @license
* Copyright 2020 Google LLC. All Rights Reserved.
* 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.
* =============================================================================
*/
import {ENGINE} from '../engine';
import {Multinomial, MultinomialAttrs, MultinomialInputs} from '../kernel_names';
import {NamedAttrMap} from '../kernel_registry';
import {Tensor1D, Tensor2D} from '../tensor';
import {NamedTensorMap} from '../tensor_types';
import {convertToTensor} from '../tensor_util_env';
import {TensorLike} from '../types';
import {op} from './operation';
import {reshape} from './reshape';
/**
* Creates a `tf.Tensor` with values drawn from a multinomial distribution.
*
* ```js
* const probs = tf.tensor([.75, .25]);
* tf.multinomial(probs, 3).print();
* ```
*
* @param logits 1D array with unnormalized log-probabilities, or
* 2D array of shape `[batchSize, numOutcomes]`. See the `normalized`
* parameter.
* @param numSamples Number of samples to draw for each row slice.
* @param seed The seed number.
* @param normalized Whether the provided `logits` are normalized true
* probabilities (sum to 1). Defaults to false.
* @return 1D array of shape `[numSamples]`, or 2D array of shape
* `[batchSize, numSamples]`, depending on the rank of the input.
*
* @doc {heading: 'Tensors', subheading: 'Random'}
*/
function multinomial_(
logits: Tensor1D|Tensor2D|TensorLike, numSamples: number, seed?: number,
normalized = false): Tensor1D|Tensor2D {
const $logits = convertToTensor(logits, 'logits', 'multinomial');
const numOutcomes = $logits.size;
const origRank = $logits.rank;
if (numOutcomes < 2) {
throw new Error(
`Error in multinomial: you need at least 2 outcomes, but got ` +
`${numOutcomes}.`);
}
if (origRank > 2) {
throw new Error(`Rank of probabilities must be 1 or 2, but is ${origRank}`);
}
// TODO(lina128): Investigate correct seed behavior. The code seems not allow
// setting see to 0.
seed = seed || Math.random();
// The kernel only accepts (and returns) rank 2 tensors.
const logits2D: Tensor2D =
origRank === 1 ? reshape($logits, [1, -1]) : $logits as Tensor2D;
const inputs: MultinomialInputs = {logits: logits2D};
const attrs: MultinomialAttrs = {numSamples, seed, normalized};
// tslint:disable-next-line: no-unnecessary-type-assertion
const res = ENGINE.runKernel(
Multinomial, inputs as unknown as NamedTensorMap,
attrs as unknown as NamedAttrMap) as Tensor2D;
// tslint:disable-next-line:no-unnecessary-type-assertion
return origRank === 1 ? reshape(res, [res.size]) as Tensor1D : res;
}
export const multinomial = /* @__PURE__ */ op({multinomial_});