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perf(js): speed up Tiktoken.encode #157

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97 changes: 58 additions & 39 deletions js/src/core.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -2,45 +2,55 @@ import base64 from "base64-js";
import type { TiktokenModel } from "./ranks/ranks";
import { never } from "./utils";

function bytePairMerge(
piece: Uint8Array,
ranks: Map<string, number>
): Array<{ start: number; end: number }> {
let parts: Array<{ start: number; end: number }> = Array.from(
{ length: piece.length },
(_, i) => ({ start: i, end: i + 1 })
);

while (parts.length > 1) {
let minRank: [number, number] | null = null;

for (let i = 0; i < parts.length - 1; i++) {
const slice = piece.slice(parts[i].start, parts[i + 1].end);
const rank = ranks.get(slice.join(","));
if (rank == null) continue;

if (minRank == null || rank < minRank[0]) {
minRank = [rank, i];
function bytesToKey(bytes: Uint8Array, start: number, end: number): string {
let key = "";
for (let i = start; i < end; i++) key += String.fromCharCode(bytes[i]);
return key;
}

function bytePairEncode(piece: Uint8Array, ranks: Map<string, number>): number[] {
const n = piece.length;
if (n === 1) return [ranks.get(bytesToKey(piece, 0, 1))!];

const starts = new Int32Array(n + 1);
for (let i = 0; i <= n; i++) starts[i] = i;
let count = n + 1;

const rank = new Float64Array(n + 1).fill(Infinity);
const rankAt = (i: number): number => {
if (i + 2 >= count) return Infinity;
const r = ranks.get(bytesToKey(piece, starts[i], starts[i + 2]));
return r === undefined ? Infinity : r;
};
for (let i = 0; i + 2 < count; i++) rank[i] = rankAt(i);

while (count > 2) {
let minRank = Infinity;
let minIdx = -1;
for (let i = 0; i + 2 < count; i++) {
if (rank[i] < minRank) {
minRank = rank[i];
minIdx = i;
}
}
if (minIdx === -1) break;

if (minRank != null) {
const i = minRank[1];
parts[i] = { start: parts[i].start, end: parts[i + 1].end };
parts.splice(i + 1, 1);
} else {
break;
for (let i = minIdx + 1; i + 1 < count; i++) {
starts[i] = starts[i + 1];
rank[i] = rank[i + 1];
}
}
return parts;
}
count--;

function bytePairEncode(piece: Uint8Array, ranks: Map<string, number>) {
if (piece.length === 1) return [ranks.get(piece.join(","))!];
rank[minIdx] = rankAt(minIdx);
if (minIdx > 0) rank[minIdx - 1] = rankAt(minIdx - 1);
}

return bytePairMerge(piece, ranks)
.map((p) => ranks.get(piece.slice(p.start, p.end).join(",")))
.filter((x): x is number => x != null);
const out: number[] = [];
for (let i = 0; i + 1 < count; i++) {
const r = ranks.get(bytesToKey(piece, starts[i], starts[i + 1]));
if (r != null) out.push(r);
}
return out;
}

function escapeRegex(str: string) {
Expand All @@ -63,6 +73,12 @@ export class Tiktoken {
/** @internal */
protected patStr: string;

/** @internal */
protected pattern: RegExp;

/** @internal */
protected specialTokensRegex: RegExp;

/** @internal */
protected textEncoder = new TextEncoder();

Expand Down Expand Up @@ -93,7 +109,7 @@ export class Tiktoken {

for (const [token, rank] of Object.entries(uncompressed)) {
const bytes = base64.toByteArray(token);
this.rankMap.set(bytes.join(","), rank);
this.rankMap.set(bytesToKey(bytes, 0, bytes.length), rank);
this.textMap.set(rank, bytes);
}

Expand All @@ -104,6 +120,11 @@ export class Tiktoken {
memo[rank] = this.textEncoder.encode(text);
return memo;
}, {});

this.pattern = new RegExp(this.patStr, "ug");
this.specialTokensRegex = Tiktoken.specialTokenRegex(
Object.keys(this.specialTokens)
);
}

private static specialTokenRegex = (tokens: string[]) => {
Expand All @@ -115,10 +136,8 @@ export class Tiktoken {
allowedSpecial: Array<string> | "all" = [],
disallowedSpecial: Array<string> | "all" = "all"
) {
const regexes = new RegExp(this.patStr, "ug");
const specialRegex = Tiktoken.specialTokenRegex(
Object.keys(this.specialTokens)
);
const regexes = this.pattern;
const specialRegex = this.specialTokensRegex;

const ret: number[] = [];

Expand Down Expand Up @@ -164,7 +183,7 @@ export class Tiktoken {
const end = nextSpecial?.index ?? text.length;
for (const match of text.substring(start, end).matchAll(regexes)) {
const piece = this.textEncoder.encode(match[0]);
const token = this.rankMap.get(piece.join(","));
const token = this.rankMap.get(bytesToKey(piece, 0, piece.length));

if (token != null) {
ret.push(token);
Expand Down