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Fix output sequence issue of lstm with backward direction and both direction #123

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Jan 14, 2025
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28 changes: 24 additions & 4 deletions src/lstm.js
Original file line number Diff line number Diff line change
Expand Up @@ -3,8 +3,10 @@
import {concat} from './concat.js';
import {lstmCell} from './lstm_cell.js';
import {reshape, squeeze} from './reshape.js';
import {reverse} from './reverse.js';
import {sizeOfShape, Tensor} from './lib/tensor.js';
import {sigmoid} from './sigmoid.js';
import {split} from './split.js';
import {slice} from './slice.js';
import {tanh} from './tanh.js';
import {validateLstmParams} from './lib/validate-input.js';
Expand Down Expand Up @@ -85,10 +87,11 @@ export function lstm(input, weight, recurrentWeight, steps, hiddenSize,
currentHidden[dir], currentCell[dir], hiddenSize, {bias: currentBias[dir],
recurrentBias: currentRecurrentBias[dir], peepholeWeight: currentPeepholeWeight[dir],
layout: layout, activations: activations});
// Expand [batchSize, hiddenSize] to [numDirections, batchSize, hiddenSize]
const output = reshape(results[0], [1, batchSize, hiddenSize]);
const cell = reshape(results[1], [1, batchSize, hiddenSize]);

const output = reshape(results[0], [1, null, hiddenSize]);
const cell = reshape(results[1], [1, null, hiddenSize]);

// Concat along 0 axis (for numDirections dimension)
nextHidden = (nextHidden ? concat([nextHidden, output], 0) : output);
nextCell = (nextCell ? concat([nextCell, cell], 0) : cell);
}
Expand All @@ -97,10 +100,27 @@ export function lstm(input, weight, recurrentWeight, steps, hiddenSize,
cellState = nextCell;

if (returnSequence) {
nextHidden = reshape(nextHidden, [1, numDirections, null, hiddenSize]);
// Expand [numDirections, batchSize, hiddenSize] to
// [steps, numDirections, batchSize, hiddenSize]
nextHidden = reshape(nextHidden, [1, numDirections, batchSize, hiddenSize]);
// Concat output sequence along 0 axis (for steps dimension)
sequence = (sequence ? concat([sequence, nextHidden], 0) : nextHidden);
}
}

if (direction === 'backward') {
// Reverse output sequence alog [0] axes (for steps dimension)
sequence = reverse(sequence, {axes: [0]});
} else if (direction === 'both') {
// Split output sequence into forward-sequence and backward-sequence two sequences along 1 axis
// (for numDirections dimension)
const [sequenceForward, sequenceBackward] = split(sequence, 2, {axis: 1});
// Reverse backward-sequence alog [0] axes (for only steps dimension)
const reversedSequenceBackward = reverse(sequenceBackward, {axes: [0]});
sequence = concat([sequenceForward, reversedSequenceBackward], 1);
} else {
// No need update sequence for 'forward' direction
}

return (sequence ? [hiddenState, cellState, sequence] : [hiddenState, cellState]);
}
74 changes: 67 additions & 7 deletions test/lstm_test.js
Original file line number Diff line number Diff line change
Expand Up @@ -45,7 +45,6 @@ describe('test lstm', function() {
input, weight, recurrentWeight, steps, hiddenSize,
{bias, recurrentBias, peepholeWeight, initialHiddenState,
initialCellState, returnSequence, activations});
console.log('outputs: ', outputs);
utils.checkShape(outputs[0], [numDirections, batchSize, hiddenSize]);
utils.checkShape(outputs[1], [numDirections, batchSize, hiddenSize]);
utils.checkShape(outputs[2], [steps, numDirections, batchSize, hiddenSize]);
Expand All @@ -65,7 +64,7 @@ describe('test lstm', function() {
}
});

it('lstm steps=2 direction="backward" returnSequence=true' +
it('lstm steps=2 direction="backward" returnSequence=true ' +
'activations=[relu, relu, relu]', function() {
const steps = 2;
const numDirections = 1;
Expand Down Expand Up @@ -106,22 +105,83 @@ describe('test lstm', function() {
input, weight, recurrentWeight, steps, hiddenSize,
{bias, recurrentBias, peepholeWeight, initialHiddenState,
initialCellState, direction, returnSequence, activations});
console.log('outputs: ', outputs);
utils.checkShape(outputs[0], [numDirections, batchSize, hiddenSize]);
utils.checkShape(outputs[1], [numDirections, batchSize, hiddenSize]);
utils.checkShape(outputs[2], [steps, numDirections, batchSize, hiddenSize]);
const expected = [
[10.469, 58.02899999999999, 74.529, 518.9490000000001],
[5.51, 20.009999999999998, 19.11, 75.21000000000001],
[
1,
8,
1,
8,
10.469,
58.02899999999999,
74.529,
518.9490000000001,
1,
8,
1,
8,
],
];
for (let i = 0; i < expected.length; ++i) {
utils.checkValue(outputs[i], expected[i]);
}
});

it('lstm steps=2 direction="both" returnSequence=true', function() {
const steps = 2;
const numDirections = 2;
const batchSize = 2;
const inputSize = 2;
const hiddenSize = 2;
const input = new Tensor([steps, batchSize, inputSize],
new Float32Array([1, 2, 2, 1, 3, 4, 1, 2]));
const weight = new Tensor([numDirections, 4 * hiddenSize, inputSize],
new Float32Array([
1, -1, 2, -2, 1, -1, 2, -2,
1, -1, 2, -2, 1, -1, 2, -2,
1, -1, 2, -2, 1, -1, 2, -2,
1, -1, 2, -2, 1, -1, 2, -2,
]));
const recurrentWeight = new Tensor([numDirections, 4 * hiddenSize, hiddenSize],
new Array(2 * 4 * hiddenSize * hiddenSize).fill(0.1));
const bias = new Tensor([numDirections, 4 * hiddenSize],
new Float32Array([
1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2,
]));
const recurrentBias = new Tensor([numDirections, 4 * hiddenSize],
new Float32Array([
1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2,
]));
const returnSequence = true;
const direction = 'both';
const outputs = lstm(
input, weight, recurrentWeight, steps, hiddenSize,
{bias, recurrentBias, direction, returnSequence});
utils.checkShape(outputs[0], [numDirections, batchSize, hiddenSize]);
utils.checkShape(outputs[1], [numDirections, batchSize, hiddenSize]);
utils.checkShape(outputs[2], [steps, numDirections, batchSize, hiddenSize]);
const expected = [
[
0.5764073262004139, 0.8236227651782412,
0.6612355785279247, 0.8442635760318142,
0.5764073262004139, 0.8236227651782412,
0.8635294727880538, 0.9491350760903781,
],
[
1.0171455721466105, 1.6205496282195793,
1.338846378789257, 1.7642604746965693,
1.0171455721466105, 1.6205496282195793,
1.485626937219704, 1.8449554199024933,
],
[
0.36960635293570576, 0.6082834181835157,
0.7037753329989016, 0.7586680430344475,
0.5764073262004139, 0.8236227651782412,
0.8635294727880538, 0.9491350760903781,
0.5764073262004139, 0.8236227651782412,
0.6612355785279247, 0.8442635760318142,
0.36960635293570576, 0.6082834181835157,
0.36960635293570576, 0.6082834181835157,
],
];
for (let i = 0; i < expected.length; ++i) {
Expand Down
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