@tensorflow/tfjs-core
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Hardware-accelerated JavaScript library for machine intelligence
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JavaScript
/**
* @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.
* =============================================================================
*/
/**
* Shuffles the array in-place using Fisher-Yates algorithm.
*
* ```js
* const a = [1, 2, 3, 4, 5];
* tf.util.shuffle(a);
* console.log(a);
* ```
*
* @param array The array to shuffle in-place.
*
* @doc {heading: 'Util', namespace: 'util'}
*/
// tslint:disable-next-line:no-any
export function shuffle(array) {
let counter = array.length;
let temp = 0;
let index = 0;
// While there are elements in the array
while (counter > 0) {
// Pick a random index
index = (Math.random() * counter) | 0;
// Decrease counter by 1
counter--;
// And swap the last element with it
temp = array[counter];
array[counter] = array[index];
array[index] = temp;
}
}
/**
* Shuffles two arrays in-place the same way using Fisher-Yates algorithm.
*
* ```js
* const a = [1,2,3,4,5];
* const b = [11,22,33,44,55];
* tf.util.shuffleCombo(a, b);
* console.log(a, b);
* ```
*
* @param array The first array to shuffle in-place.
* @param array2 The second array to shuffle in-place with the same permutation
* as the first array.
*
* @doc {heading: 'Util', namespace: 'util'}
*/
// tslint:disable-next-line:no-any
export function shuffleCombo(array,
// tslint:disable-next-line:no-any
array2) {
if (array.length !== array2.length) {
throw new Error(`Array sizes must match to be shuffled together ` +
`First array length was ${array.length}` +
`Second array length was ${array2.length}`);
}
let counter = array.length;
let temp, temp2;
let index = 0;
// While there are elements in the array
while (counter > 0) {
// Pick a random index
index = (Math.random() * counter) | 0;
// Decrease counter by 1
counter--;
// And swap the last element of each array with it
temp = array[counter];
temp2 = array2[counter];
array[counter] = array[index];
array2[counter] = array2[index];
array[index] = temp;
array2[index] = temp2;
}
}
/** Clamps a value to a specified range. */
export function clamp(min, x, max) {
return Math.max(min, Math.min(x, max));
}
export function nearestLargerEven(val) {
return val % 2 === 0 ? val : val + 1;
}
export function sum(arr) {
let sum = 0;
for (let i = 0; i < arr.length; i++) {
sum += arr[i];
}
return sum;
}
/**
* Returns a sample from a uniform [a, b) distribution.
*
* @param a The minimum support (inclusive).
* @param b The maximum support (exclusive).
* @return A pseudorandom number on the half-open interval [a,b).
*/
export function randUniform(a, b) {
const r = Math.random();
return (b * r) + (1 - r) * a;
}
/** Returns the squared Euclidean distance between two vectors. */
export function distSquared(a, b) {
let result = 0;
for (let i = 0; i < a.length; i++) {
const diff = Number(a[i]) - Number(b[i]);
result += diff * diff;
}
return result;
}
/**
* Asserts that the expression is true. Otherwise throws an error with the
* provided message.
*
* ```js
* const x = 2;
* tf.util.assert(x === 2, 'x is not 2');
* ```
*
* @param expr The expression to assert (as a boolean).
* @param msg A function that returns the message to report when throwing an
* error. We use a function for performance reasons.
*
* @doc {heading: 'Util', namespace: 'util'}
*/
export function assert(expr, msg) {
if (!expr) {
throw new Error(typeof msg === 'string' ? msg : msg());
}
}
export function assertShapesMatch(shapeA, shapeB, errorMessagePrefix = '') {
assert(arraysEqual(shapeA, shapeB), () => errorMessagePrefix + ` Shapes ${shapeA} and ${shapeB} must match`);
}
export function assertNonNull(a) {
assert(a != null, () => `The input to the tensor constructor must be a non-null value.`);
}
// NOTE: We explicitly type out what T extends instead of any so that
// util.flatten on a nested array of number doesn't try to infer T as a
// number[][], causing us to explicitly type util.flatten<number>().
/**
* Flattens an arbitrarily nested array.
*
* ```js
* const a = [[1, 2], [3, 4], [5, [6, [7]]]];
* const flat = tf.util.flatten(a);
* console.log(flat);
* ```
*
* @param arr The nested array to flatten.
* @param result The destination array which holds the elements.
* @param skipTypedArray If true, avoids flattening the typed arrays. Defaults
* to false.
*
* @doc {heading: 'Util', namespace: 'util'}
*/
export function flatten(arr, result = [], skipTypedArray = false) {
if (result == null) {
result = [];
}
if (Array.isArray(arr) || isTypedArray(arr) && !skipTypedArray) {
for (let i = 0; i < arr.length; ++i) {
flatten(arr[i], result, skipTypedArray);
}
}
else {
result.push(arr);
}
return result;
}
/**
* Returns the size (number of elements) of the tensor given its shape.
*
* ```js
* const shape = [3, 4, 2];
* const size = tf.util.sizeFromShape(shape);
* console.log(size);
* ```
*
* @doc {heading: 'Util', namespace: 'util'}
*/
export function sizeFromShape(shape) {
if (shape.length === 0) {
// Scalar.
return 1;
}
let size = shape[0];
for (let i = 1; i < shape.length; i++) {
size *= shape[i];
}
return size;
}
export function isScalarShape(shape) {
return shape.length === 0;
}
export function arraysEqual(n1, n2) {
if (n1 === n2) {
return true;
}
if (n1 == null || n2 == null) {
return false;
}
if (n1.length !== n2.length) {
return false;
}
for (let i = 0; i < n1.length; i++) {
if (n1[i] !== n2[i]) {
return false;
}
}
return true;
}
export function isInt(a) {
return a % 1 === 0;
}
export function tanh(x) {
// tslint:disable-next-line:no-any
if (Math.tanh != null) {
// tslint:disable-next-line:no-any
return Math.tanh(x);
}
if (x === Infinity) {
return 1;
}
else if (x === -Infinity) {
return -1;
}
else {
const e2x = Math.exp(2 * x);
return (e2x - 1) / (e2x + 1);
}
}
export function sizeToSquarishShape(size) {
const width = Math.ceil(Math.sqrt(size));
return [width, Math.ceil(size / width)];
}
/**
* Creates a new array with randomized indicies to a given quantity.
*
* ```js
* const randomTen = tf.util.createShuffledIndices(10);
* console.log(randomTen);
* ```
*
* @param number Quantity of how many shuffled indicies to create.
*
* @doc {heading: 'Util', namespace: 'util'}
*/
export function createShuffledIndices(n) {
const shuffledIndices = new Uint32Array(n);
for (let i = 0; i < n; ++i) {
shuffledIndices[i] = i;
}
shuffle(shuffledIndices);
return shuffledIndices;
}
export function rightPad(a, size) {
if (size <= a.length) {
return a;
}
return a + ' '.repeat(size - a.length);
}
export function repeatedTry(checkFn, delayFn = (counter) => 0, maxCounter) {
return new Promise((resolve, reject) => {
let tryCount = 0;
const tryFn = () => {
if (checkFn()) {
resolve();
return;
}
tryCount++;
const nextBackoff = delayFn(tryCount);
if (maxCounter != null && tryCount >= maxCounter) {
reject();
return;
}
setTimeout(tryFn, nextBackoff);
};
tryFn();
});
}
/**
* Given the full size of the array and a shape that may contain -1 as the
* implicit dimension, returns the inferred shape where -1 is replaced.
* E.g. For shape=[2, -1, 3] and size=24, it will return [2, 4, 3].
*
* @param shape The shape, which may contain -1 in some dimension.
* @param size The full size (number of elements) of the array.
* @return The inferred shape where -1 is replaced with the inferred size.
*/
export function inferFromImplicitShape(shape, size) {
let shapeProd = 1;
let implicitIdx = -1;
for (let i = 0; i < shape.length; ++i) {
if (shape[i] >= 0) {
shapeProd *= shape[i];
}
else if (shape[i] === -1) {
if (implicitIdx !== -1) {
throw Error(`Shapes can only have 1 implicit size. ` +
`Found -1 at dim ${implicitIdx} and dim ${i}`);
}
implicitIdx = i;
}
else if (shape[i] < 0) {
throw Error(`Shapes can not be < 0. Found ${shape[i]} at dim ${i}`);
}
}
if (implicitIdx === -1) {
if (size > 0 && size !== shapeProd) {
throw Error(`Size(${size}) must match the product of shape ${shape}`);
}
return shape;
}
if (shapeProd === 0) {
throw Error(`Cannot infer the missing size in [${shape}] when ` +
`there are 0 elements`);
}
if (size % shapeProd !== 0) {
throw Error(`The implicit shape can't be a fractional number. ` +
`Got ${size} / ${shapeProd}`);
}
const newShape = shape.slice();
newShape[implicitIdx] = size / shapeProd;
return newShape;
}
export function parseAxisParam(axis, shape) {
const rank = shape.length;
// Normalize input
axis = axis == null ? shape.map((s, i) => i) : [].concat(axis);
// Check for valid range
assert(axis.every(ax => ax >= -rank && ax < rank), () => `All values in axis param must be in range [-${rank}, ${rank}) but ` +
`got axis ${axis}`);
// Check for only integers
assert(axis.every(ax => isInt(ax)), () => `All values in axis param must be integers but ` +
`got axis ${axis}`);
// Handle negative axis.
return axis.map(a => a < 0 ? rank + a : a);
}
/** Reduces the shape by removing all dimensions of shape 1. */
export function squeezeShape(shape, axis) {
const newShape = [];
const keptDims = [];
const isEmptyArray = axis != null && Array.isArray(axis) && axis.length === 0;
const axes = (axis == null || isEmptyArray) ?
null :
parseAxisParam(axis, shape).sort();
let j = 0;
for (let i = 0; i < shape.length; ++i) {
if (axes != null) {
if (axes[j] === i && shape[i] !== 1) {
throw new Error(`Can't squeeze axis ${i} since its dim '${shape[i]}' is not 1`);
}
if ((axes[j] == null || axes[j] > i) && shape[i] === 1) {
newShape.push(shape[i]);
keptDims.push(i);
}
if (axes[j] <= i) {
j++;
}
}
if (shape[i] !== 1) {
newShape.push(shape[i]);
keptDims.push(i);
}
}
return { newShape, keptDims };
}
export function getTypedArrayFromDType(dtype, size) {
let values = null;
if (dtype == null || dtype === 'float32') {
values = new Float32Array(size);
}
else if (dtype === 'int32') {
values = new Int32Array(size);
}
else if (dtype === 'bool') {
values = new Uint8Array(size);
}
else {
throw new Error(`Unknown data type ${dtype}`);
}
return values;
}
export function getArrayFromDType(dtype, size) {
let values = null;
if (dtype == null || dtype === 'float32') {
values = new Float32Array(size);
}
else if (dtype === 'int32') {
values = new Int32Array(size);
}
else if (dtype === 'bool') {
values = new Uint8Array(size);
}
else if (dtype === 'string') {
values = new Array(size);
}
else {
throw new Error(`Unknown data type ${dtype}`);
}
return values;
}
export function checkConversionForErrors(vals, dtype) {
for (let i = 0; i < vals.length; i++) {
const num = vals[i];
if (isNaN(num) || !isFinite(num)) {
throw Error(`A tensor of type ${dtype} being uploaded contains ${num}.`);
}
}
}
/** Returns true if the dtype is valid. */
export function isValidDtype(dtype) {
return dtype === 'bool' || dtype === 'complex64' || dtype === 'float32' ||
dtype === 'int32' || dtype === 'string';
}
/**
* Returns true if the new type can't encode the old type without loss of
* precision.
*/
export function hasEncodingLoss(oldType, newType) {
if (newType === 'complex64') {
return false;
}
if (newType === 'float32' && oldType !== 'complex64') {
return false;
}
if (newType === 'int32' && oldType !== 'float32' && oldType !== 'complex64') {
return false;
}
if (newType === 'bool' && oldType === 'bool') {
return false;
}
return true;
}
export function isTypedArray(a) {
return a instanceof Float32Array || a instanceof Int32Array ||
a instanceof Uint8Array;
}
export function bytesPerElement(dtype) {
if (dtype === 'float32' || dtype === 'int32') {
return 4;
}
else if (dtype === 'complex64') {
return 8;
}
else if (dtype === 'bool') {
return 1;
}
else {
throw new Error(`Unknown dtype ${dtype}`);
}
}
/**
* Returns the approximate number of bytes allocated in the string array - 2
* bytes per character. Computing the exact bytes for a native string in JS is
* not possible since it depends on the encoding of the html page that serves
* the website.
*/
export function bytesFromStringArray(arr) {
if (arr == null) {
return 0;
}
let bytes = 0;
arr.forEach(x => bytes += x.length);
return bytes;
}
/** Returns true if the value is a string. */
export function isString(value) {
return typeof value === 'string' || value instanceof String;
}
export function isBoolean(value) {
return typeof value === 'boolean';
}
export function isNumber(value) {
return typeof value === 'number';
}
export function inferDtype(values) {
if (Array.isArray(values)) {
return inferDtype(values[0]);
}
if (values instanceof Float32Array) {
return 'float32';
}
else if (values instanceof Int32Array || values instanceof Uint8Array) {
return 'int32';
}
else if (isNumber(values)) {
return 'float32';
}
else if (isString(values)) {
return 'string';
}
else if (isBoolean(values)) {
return 'bool';
}
return 'float32';
}
export function isFunction(f) {
return !!(f && f.constructor && f.call && f.apply);
}
export function nearestDivisor(size, start) {
for (let i = start; i < size; ++i) {
if (size % i === 0) {
return i;
}
}
return size;
}
export function computeStrides(shape) {
const rank = shape.length;
if (rank < 2) {
return [];
}
// Last dimension has implicit stride of 1, thus having D-1 (instead of D)
// strides.
const strides = new Array(rank - 1);
strides[rank - 2] = shape[rank - 1];
for (let i = rank - 3; i >= 0; --i) {
strides[i] = strides[i + 1] * shape[i + 1];
}
return strides;
}
function createNestedArray(offset, shape, a) {
const ret = new Array();
if (shape.length === 1) {
const d = shape[0];
for (let i = 0; i < d; i++) {
ret[i] = a[offset + i];
}
}
else {
const d = shape[0];
const rest = shape.slice(1);
const len = rest.reduce((acc, c) => acc * c);
for (let i = 0; i < d; i++) {
ret[i] = createNestedArray(offset + i * len, rest, a);
}
}
return ret;
}
// Provide a nested array of TypedArray in given shape.
export function toNestedArray(shape, a) {
if (shape.length === 0) {
// Scalar type should return a single number.
return a[0];
}
const size = shape.reduce((acc, c) => acc * c);
if (size === 0) {
// A tensor with shape zero should be turned into empty list.
return [];
}
if (size !== a.length) {
throw new Error(`[${shape}] does not match the input size ${a.length}.`);
}
return createNestedArray(0, shape, a);
}
export function makeOnesTypedArray(size, dtype) {
const array = makeZerosTypedArray(size, dtype);
for (let i = 0; i < array.length; i++) {
array[i] = 1;
}
return array;
}
export function makeZerosTypedArray(size, dtype) {
if (dtype == null || dtype === 'float32' || dtype === 'complex64') {
return new Float32Array(size);
}
else if (dtype === 'int32') {
return new Int32Array(size);
}
else if (dtype === 'bool') {
return new Uint8Array(size);
}
else {
throw new Error(`Unknown data type ${dtype}`);
}
}
/**
* Make nested `TypedArray` filled with zeros.
* @param shape The shape information for the nested array.
* @param dtype dtype of the array element.
*/
export function makeZerosNestedTypedArray(shape, dtype) {
const size = shape.reduce((prev, curr) => prev * curr, 1);
if (dtype == null || dtype === 'float32') {
return toNestedArray(shape, new Float32Array(size));
}
else if (dtype === 'int32') {
return toNestedArray(shape, new Int32Array(size));
}
else if (dtype === 'bool') {
return toNestedArray(shape, new Uint8Array(size));
}
else {
throw new Error(`Unknown data type ${dtype}`);
}
}
export function assertNonNegativeIntegerDimensions(shape) {
shape.forEach(dimSize => {
assert(Number.isInteger(dimSize) && dimSize >= 0, () => `Tensor must have a shape comprised of positive integers but got ` +
`shape [${shape}].`);
});
}
/**
* Computes flat index for a given location (multidimentionsal index) in a
* Tensor/multidimensional array.
*
* @param locs Location in the tensor.
* @param rank Rank of the tensor.
* @param strides Tensor strides.
*/
export function locToIndex(locs, rank, strides) {
if (rank === 0) {
return 0;
}
else if (rank === 1) {
return locs[0];
}
let index = locs[locs.length - 1];
for (let i = 0; i < locs.length - 1; ++i) {
index += strides[i] * locs[i];
}
return index;
}
/**
* Computes the location (multidimensional index) in a tensor/multidimentional
* array for a given flat index.
*
* @param index Index in flat array.
* @param rank Rank of tensor.
* @param strides Strides of tensor.
*/
export function indexToLoc(index, rank, strides) {
if (rank === 0) {
return [];
}
else if (rank === 1) {
return [index];
}
const locs = new Array(rank);
for (let i = 0; i < locs.length - 1; ++i) {
locs[i] = Math.floor(index / strides[i]);
index -= locs[i] * strides[i];
}
locs[locs.length - 1] = index;
return locs;
}
/**
* This method asserts whether an object is a Promise instance.
* @param object
*/
// tslint:disable-next-line: no-any
export function isPromise(object) {
// We chose to not use 'obj instanceOf Promise' for two reasons:
// 1. It only reliably works for es6 Promise, not other Promise
// implementations.
// 2. It doesn't work with framework that uses zone.js. zone.js monkey patch
// the async calls, so it is possible the obj (patched) is comparing to a
// pre-patched Promise.
return object && object.then && typeof object.then === 'function';
}
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