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feat: implement HashComputationLevel using LinkedList (#389)
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* feat: implement HashComputationLevel using LinkedList

* feat: set default hasher to hashtree for benchmark

* fix: HashComputationLevel.reset()

* chore: add benchmark result

* fix: implement IterableIterator and add more comments
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twoeths authored Aug 6, 2024
1 parent 8ea1bb4 commit e2c8329
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232 changes: 232 additions & 0 deletions packages/persistent-merkle-tree/src/hashComputation.ts
Original file line number Diff line number Diff line change
@@ -0,0 +1,232 @@
import type {Node} from "./node";

/**
* HashComputation to be later used to compute hash of nodes from bottom up.
* This is also an item of a linked list.
* ╔═════════════════════╗ ╔══════════════════════╗
* ║ dest ║ ║ next_dest ║
* ║ / \ ║ ========> ║ / \ ║
* ║ src0 src1 ║ ║ next_src0 next_src1║
* ╚═════════════════════╝ ╚══════════════════════╝
*/
export type HashComputation = {
src0: Node;
src1: Node;
dest: Node;
next: HashComputation | null;
};

/**
* Model HashComputation[] at the same level that support reusing the same memory.
* Before every run, reset() should be called.
* After every run, clean() should be called.
*/
export class HashComputationLevel implements IterableIterator<HashComputation> {
private _length: number;
private _totalLength: number;
// use LinkedList to avoid memory allocation when the list grows
// always have a fixed head although length is 0
private head: HashComputation;
private tail: HashComputation | null;
private pointer: HashComputation | null;

constructor() {
this._length = 0;
this._totalLength = 0;
this.head = {
src0: null as unknown as Node,
src1: null as unknown as Node,
dest: null as unknown as Node,
next: null,
};
this.tail = null;
this.pointer = null;
}

get length(): number {
return this._length;
}

get totalLength(): number {
return this._totalLength;
}

/**
* run before every run
*/
reset(): void {
// keep this.head object, only release the data
this.head.src0 = null as unknown as Node;
this.head.src1 = null as unknown as Node;
this.head.dest = null as unknown as Node;
this.tail = null;
this._length = 0;
// totalLength is not reset
this.pointer = null;
}

/**
* Append a new HashComputation to tail.
* This will overwrite the existing HashComputation if it is not null, or grow the list if needed.
*/
push(src0: Node, src1: Node, dest: Node): void {
if (this.tail !== null) {
let newTail = this.tail.next;
if (newTail !== null) {
newTail.src0 = src0;
newTail.src1 = src1;
newTail.dest = dest;
} else {
// grow the list
newTail = {src0, src1, dest, next: null};
this.tail.next = newTail;
this._totalLength++;
}
this.tail = newTail;
this._length++;
return;
}

// first item
this.head.src0 = src0;
this.head.src1 = src1;
this.head.dest = dest;
this.tail = this.head;
this._length = 1;
if (this._totalLength === 0) {
this._totalLength = 1;
}
// else _totalLength > 0, do not set
}

/**
* run after every run
* hashComps may still refer to the old Nodes, we should release them to avoid memory leak.
*/
clean(): void {
let hc = this.tail?.next ?? null;
while (hc !== null) {
if (hc.src0 === null) {
// we may have already cleaned it in the previous run, return early
break;
}
hc.src0 = null as unknown as Node;
hc.src1 = null as unknown as Node;
hc.dest = null as unknown as Node;
hc = hc.next;
}
}

/**
* Implement Iterator for this class
*/
next(): IteratorResult<HashComputation> {
if (!this.pointer || this.tail === null) {
return {done: true, value: undefined};
}

// never yield value beyond the tail
const value = this.pointer;
const isNull = value.src0 === null;
this.pointer = this.pointer.next;

return isNull ? {done: true, value: undefined} : {done: false, value};
}

/**
* This is convenient method to consume HashComputationLevel with for-of loop
* See "next" method above for the actual implementation
*/
[Symbol.iterator](): IterableIterator<HashComputation> {
this.pointer = this.head;
return this;
}

/**
* Not great due to memory allocation, for testing only.
* This converts all HashComputation with data to an array.
*/
toArray(): HashComputation[] {
const hashComps: HashComputation[] = [];
for (const hc of this) {
hashComps.push(hc);
}
return hashComps;
}

/**
* For testing only.
* This dumps all backed HashComputation objects, note that some HashComputation may not have data.
*/
dump(): HashComputation[] {
const hashComps: HashComputation[] = [];
let hc: HashComputation | null = null;
for (hc = this.head; hc !== null; hc = hc.next) {
hashComps.push(hc);
}
return hashComps;
}
}

/**
* Model HashComputationLevel[] at different levels.
*/
export class HashComputationGroup {
readonly byLevel: HashComputationLevel[];
constructor() {
this.byLevel = [];
}

reset(): void {
for (const level of this.byLevel) {
level.reset();
}
}

clean(): void {
for (const level of this.byLevel) {
level.clean();
}
}
}

/**
* Get HashComputations from a root node all the way to the leaf nodes.
* hcByLevel is the global array to store HashComputationLevel at different levels
* at this ${node}, we only add more HashComputations starting from ${index}
*
* ╔═══ hcByLevel ══════╗
* ║ level 0 ║
* ║ level 1 ║
* ║ ... ║
* ║ ║ node
* ║ ║ / \
* ║ level ${index} ║ 01 02
* ║ ║ / \ / \
* ║ level ${index + 1} ║ 03 04 05 06
* ║ ║
* ║ ... ║
* ╚════════════════════╝
*/
export function getHashComputations(node: Node, index: number, hcByLevel: HashComputationLevel[]): void {
if (node.h0 === null) {
const hashComputations = levelAtIndex(hcByLevel, index);
const {left, right} = node;
hashComputations.push(left, right, node);
// leaf nodes should have h0 to stop the recursion
getHashComputations(left, index + 1, hcByLevel);
getHashComputations(right, index + 1, hcByLevel);
}

// else stop the recursion, node is hashed
}

/**
* Utility to get HashComputationLevel at a specific index.
*/
export function levelAtIndex(hcByLevel: HashComputationLevel[], index: number): HashComputationLevel {
if (hcByLevel[index] === undefined) {
hcByLevel[index] = new HashComputationLevel();
}
return hcByLevel[index];
}
9 changes: 6 additions & 3 deletions packages/persistent-merkle-tree/src/hasher/as-sha256.ts
Original file line number Diff line number Diff line change
Expand Up @@ -6,7 +6,8 @@ import {
hashInto,
} from "@chainsafe/as-sha256";
import type {Hasher} from "./types";
import {HashComputation, Node} from "../node";
import {Node} from "../node";
import type {HashComputationLevel} from "../hashComputation";
import {doDigestNLevel, doMerkleizeInto} from "./util";

export const hasher: Hasher = {
Expand All @@ -19,7 +20,7 @@ export const hasher: Hasher = {
digestNLevel(data: Uint8Array, nLevel: number): Uint8Array {
return doDigestNLevel(data, nLevel, hashInto);
},
executeHashComputations: (hashComputations: HashComputation[][]) => {
executeHashComputations: (hashComputations: HashComputationLevel[]) => {
for (let level = hashComputations.length - 1; level >= 0; level--) {
const hcArr = hashComputations[level];
if (!hcArr) {
Expand All @@ -46,7 +47,8 @@ export const hasher: Hasher = {
let src1_3: Node | null = null;
let dest3: Node | null = null;

for (const [i, hc] of hcArr.entries()) {
let i = 0;
for (const hc of hcArr) {
const indexInBatch = i % 4;

switch (indexInBatch) {
Expand Down Expand Up @@ -121,6 +123,7 @@ export const hasher: Hasher = {
default:
throw Error(`Unexpected indexInBatch ${indexInBatch}`);
}
i++;
}

// remaining
Expand Down
25 changes: 14 additions & 11 deletions packages/persistent-merkle-tree/src/hasher/hashtree.ts
Original file line number Diff line number Diff line change
@@ -1,6 +1,7 @@
import {hashInto} from "@chainsafe/hashtree";
import {Hasher, HashObject} from "./types";
import {HashComputation, Node} from "../node";
import {Node} from "../node";
import type {HashComputationLevel} from "../hashComputation";
import {byteArrayIntoHashObject} from "@chainsafe/as-sha256/lib/hashObject";
import {doDigestNLevel, doMerkleizeInto} from "./util";

Expand All @@ -20,6 +21,8 @@ const uint8Output = new Uint8Array(PARALLEL_FACTOR * 32);
// convenient reusable Uint8Array for hash64
const hash64Input = uint8Input.subarray(0, 64);
const hash64Output = uint8Output.subarray(0, 32);
// size input array to 2 HashObject per computation * 32 bytes per object
const destNodes: Node[] = new Array<Node>(PARALLEL_FACTOR);

export const hasher: Hasher = {
name: "hashtree",
Expand All @@ -43,7 +46,7 @@ export const hasher: Hasher = {
digestNLevel(data: Uint8Array, nLevel: number): Uint8Array {
return doDigestNLevel(data, nLevel, hashInto);
},
executeHashComputations(hashComputations: HashComputation[][]): void {
executeHashComputations(hashComputations: HashComputationLevel[]): void {
for (let level = hashComputations.length - 1; level >= 0; level--) {
const hcArr = hashComputations[level];
if (!hcArr) {
Expand All @@ -56,25 +59,25 @@ export const hasher: Hasher = {
continue;
}

// size input array to 2 HashObject per computation * 32 bytes per object
// const input: Uint8Array = Uint8Array.from(new Array(hcArr.length * 2 * 32));
let destNodes: Node[] = [];

// hash every 16 inputs at once to avoid memory allocation
for (const [i, {src0, src1, dest}] of hcArr.entries()) {
let i = 0;
for (const {src0, src1, dest} of hcArr) {
if (!src0 || !src1 || !dest) {
throw new Error(`Invalid HashComputation at index ${i}`);
}
const indexInBatch = i % PARALLEL_FACTOR;
const offset = indexInBatch * 16;

hashObjectToUint32Array(src0, uint32Input, offset);
hashObjectToUint32Array(src1, uint32Input, offset + 8);
destNodes.push(dest);
destNodes[indexInBatch] = dest;
if (indexInBatch === PARALLEL_FACTOR - 1) {
hashInto(uint8Input, uint8Output);
for (const [j, destNode] of destNodes.entries()) {
byteArrayIntoHashObject(uint8Output, j * 32, destNode);
}
destNodes = [];
}
i++;
}

const remaining = hcArr.length % PARALLEL_FACTOR;
Expand All @@ -84,8 +87,8 @@ export const hasher: Hasher = {
const remainingOutput = uint8Output.subarray(0, remaining * 32);
hashInto(remainingInput, remainingOutput);
// destNodes was prepared above
for (const [i, destNode] of destNodes.entries()) {
byteArrayIntoHashObject(remainingOutput, i * 32, destNode);
for (let j = 0; j < remaining; j++) {
byteArrayIntoHashObject(remainingOutput, j * 32, destNodes[j]);
}
}
}
Expand Down
4 changes: 2 additions & 2 deletions packages/persistent-merkle-tree/src/hasher/index.ts
Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
import {Hasher} from "./types";
import {hasher as nobleHasher} from "./noble";
import type {HashComputation} from "../node";
import type {HashComputationLevel} from "../hashComputation";

export * from "./types";
export * from "./util";
Expand Down Expand Up @@ -31,6 +31,6 @@ export function merkleizeInto(data: Uint8Array, padFor: number, output: Uint8Arr
hasher.merkleizeInto(data, padFor, output, offset);
}

export function executeHashComputations(hashComputations: HashComputation[][]): void {
export function executeHashComputations(hashComputations: HashComputationLevel[]): void {
hasher.executeHashComputations(hashComputations);
}
4 changes: 2 additions & 2 deletions packages/persistent-merkle-tree/src/hasher/types.ts
Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
import type {HashObject} from "@chainsafe/as-sha256/lib/hashObject";
import type {HashComputation} from "../node";
import type {HashComputationLevel} from "../hashComputation";

export type {HashObject};

Expand Down Expand Up @@ -29,5 +29,5 @@ export type Hasher = {
/**
* Execute a batch of HashComputations
*/
executeHashComputations(hashComputations: HashComputation[][]): void;
executeHashComputations(hashComputations: HashComputationLevel[]): void;
};
1 change: 1 addition & 0 deletions packages/persistent-merkle-tree/src/index.ts
Original file line number Diff line number Diff line change
@@ -1,6 +1,7 @@
export * from "./gindex";
export * from "./hasher";
export * from "./node";
export * from "./hashComputation";
export * from "./packedNode";
export * from "./proof";
export * from "./subtree";
Expand Down
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