Project early difficulty from sliding window

backend/src/__tests__/api/difficulty-adjustment.test.ts

@@ -11,9 +11,35 @@ describe('Mempool Difficulty Adjustment', () => {
     };
 
     const vectors = [
-      [ // Vector 1
+      [ // Vector 1 (normal adjustment)
+        [ // Inputs
+          dt('2024-02-02T15:42:06.000Z'), // Last DA time (in seconds)
+          dt('2024-02-08T14:43:05.000Z'), // timestamp of 504 blocks ago (in seconds)
+          dt('2024-02-11T22:43:01.000Z'), // Current time (now) (in seconds)
+          830027,                         // Current block height
+          7.333505241141637,             // Previous retarget % (Passed through)
+          'mainnet',                      // Network (if testnet, next value is non-zero)
+          0,                              // Latest block timestamp in seconds (only used if difficulty already locked in)
+        ],
+        { // Expected Result
+          progressPercent: 71.97420634920636,
+          difficultyChange: 8.512745140778843,
+          estimatedRetargetDate: 1708004001715,
+          remainingBlocks: 565,
+          remainingTime: 312620715,
+          previousRetarget: 7.333505241141637,
+          previousTime: 1706888526,
+          nextRetargetHeight: 830592,
+          timeAvg: 553311,
+          adjustedTimeAvg: 553311,
+          timeOffset: 0,
+          expectedBlocks: 1338.0916666666667,
+        },
+      ],
+      [ // Vector 2 (within quarter-epoch overlap)
         [ // Inputs
           dt('2022-08-18T11:07:00.000Z'), // Last DA time (in seconds)
+          dt('2022-08-16T03:16:54.000Z'), // timestamp of 504 blocks ago (in seconds)
           dt('2022-08-19T14:03:53.000Z'), // Current time (now) (in seconds)
           750134,                         // Current block height
           0.6280047707459726,             // Previous retarget % (Passed through)
@@ -22,21 +48,23 @@ describe('Mempool Difficulty Adjustment', () => {
         ],
         { // Expected Result
           progressPercent: 9.027777777777777,
-          difficultyChange: 13.180707740199772,
+          difficultyChange: 1.0420538959004633,
-          estimatedRetargetDate: 1661895424692,
+          estimatedRetargetDate: 1662009048328,
           remainingBlocks: 1834,
-          remainingTime: 977591692,
+          remainingTime: 1091215328,
           previousRetarget: 0.6280047707459726,
           previousTime: 1660820820,
           nextRetargetHeight: 751968,
           timeAvg: 533038,
+          adjustedTimeAvg: 594992,
           timeOffset: 0,
           expectedBlocks: 161.68833333333333,
         },
       ],
-      [ // Vector 2 (testnet)
+      [ // Vector 3 (testnet)
         [ // Inputs
           dt('2022-08-18T11:07:00.000Z'), // Last DA time (in seconds)
+          dt('2022-08-16T03:16:54.000Z'), // timestamp of 504 blocks ago (in seconds)
           dt('2022-08-19T14:03:53.000Z'), // Current time (now) (in seconds)
           750134,                         // Current block height
           0.6280047707459726,             // Previous retarget % (Passed through)
@@ -45,22 +73,24 @@ describe('Mempool Difficulty Adjustment', () => {
         ],
         { // Expected Result is same other than timeOffset
           progressPercent: 9.027777777777777,
-          difficultyChange: 13.180707740199772,
+          difficultyChange: 1.0420538959004633,
-          estimatedRetargetDate: 1661895424692,
+          estimatedRetargetDate: 1662009048328,
           remainingBlocks: 1834,
-          remainingTime: 977591692,
+          remainingTime: 1091215328,
           previousTime: 1660820820,
           previousRetarget: 0.6280047707459726,
           nextRetargetHeight: 751968,
           timeAvg: 533038,
+          adjustedTimeAvg: 594992,
           timeOffset: -667000, // 11 min 7 seconds since last block (testnet only)
           // If we add time avg to abs(timeOffset) it makes exactly 1200000 ms, or 20 minutes
           expectedBlocks: 161.68833333333333,
         },
       ],
-      [ // Vector 3 (mainnet lock-in (epoch ending 788255))
+      [ // Vector 4 (mainnet lock-in (epoch ending 788255))
         [ // Inputs
           dt('2023-04-20T09:57:33.000Z'), // Last DA time (in seconds)
+          dt('2022-08-16T03:16:54.000Z'), // timestamp of 504 blocks ago (in seconds)
           dt('2023-05-04T14:54:09.000Z'), // Current time (now) (in seconds)
           788255,                         // Current block height
           1.7220298879531821,             // Previous retarget % (Passed through)
@@ -77,16 +107,17 @@ describe('Mempool Difficulty Adjustment', () => {
           previousTime: 1681984653,
           nextRetargetHeight: 788256,
           timeAvg: 609129,
+          adjustedTimeAvg: 609129,
           timeOffset: 0,
           expectedBlocks: 2045.66,
         },
       ],
-    ] as [[number, number, number, number, string, number], DifficultyAdjustment][];
+    ] as [[number, number, number, number, number, string, number], DifficultyAdjustment][];
 
     for (const vector of vectors) {
       const result = calcDifficultyAdjustment(...vector[0]);
       // previousRetarget is passed through untouched
-      expect(result.previousRetarget).toStrictEqual(vector[0][3]);
+      expect(result.previousRetarget).toStrictEqual(vector[0][4]);
       expect(result).toStrictEqual(vector[1]);
     }
   });

backend/src/api/blocks.ts

@@ -37,6 +37,7 @@ class Blocks {
   private currentBits = 0;
   private lastDifficultyAdjustmentTime = 0;
   private previousDifficultyRetarget = 0;
+  private quarterEpochBlockTime: number | null = null;
   private newBlockCallbacks: ((block: BlockExtended, txIds: string[], transactions: TransactionExtended[]) => void)[] = [];
   private newAsyncBlockCallbacks: ((block: BlockExtended, txIds: string[], transactions: MempoolTransactionExtended[]) => Promise<void>)[] = [];
 
@@ -775,6 +776,16 @@ class Blocks {
     } else {
       this.currentBlockHeight = this.blocks[this.blocks.length - 1].height;
     }
+    if (this.currentBlockHeight >= 503) {
+      try {
+        const quarterEpochBlockHash = await bitcoinApi.$getBlockHash(this.currentBlockHeight - 503);
+        const quarterEpochBlock = await bitcoinApi.$getBlock(quarterEpochBlockHash);
+        this.quarterEpochBlockTime = quarterEpochBlock?.timestamp;
+      } catch (e) {
+        this.quarterEpochBlockTime = null;
+        logger.warn('failed to update last epoch block time: ' + (e instanceof Error ? e.message : e));
+      }
+    }
 
     if (blockHeightTip - this.currentBlockHeight > config.MEMPOOL.INITIAL_BLOCKS_AMOUNT * 2) {
       logger.info(`${blockHeightTip - this.currentBlockHeight} blocks since tip. Fast forwarding to the ${config.MEMPOOL.INITIAL_BLOCKS_AMOUNT} recent blocks`);
@@ -1308,6 +1319,10 @@ class Blocks {
     return this.previousDifficultyRetarget;
   }
 
+  public getQuarterEpochBlockTime(): number | null {
+    return this.quarterEpochBlockTime;
+  }
+
   public getCurrentBlockHeight(): number {
     return this.currentBlockHeight;
   }

backend/src/api/difficulty-adjustment.ts

@@ -12,6 +12,7 @@ export interface DifficultyAdjustment {
   previousTime: number;          // Unix time in ms
   nextRetargetHeight: number;    // Block Height
   timeAvg: number;               // Duration of time in ms
+  adjustedTimeAvg;               // Expected block interval with hashrate implied over last 504 blocks
   timeOffset: number;            // (Testnet) Time since last block (cap @ 20min) in ms
   expectedBlocks: number;         // Block count
 }
@@ -80,6 +81,7 @@ export function calcBitsDifference(oldBits: number, newBits: number): number {
 
 export function calcDifficultyAdjustment(
   DATime: number,
+  quarterEpochTime: number | null,
   nowSeconds: number,
   blockHeight: number,
   previousRetarget: number,
@@ -100,8 +102,20 @@ export function calcDifficultyAdjustment(
 
   let difficultyChange = 0;
   let timeAvgSecs = blocksInEpoch ? diffSeconds / blocksInEpoch : BLOCK_SECONDS_TARGET;
+  let adjustedTimeAvgSecs = timeAvgSecs;
 
+  // for the first 504 blocks of the epoch, calculate the expected avg block interval
+  // from a sliding window over the last 504 blocks
+  if (quarterEpochTime && blocksInEpoch < 503) {
+    const timeLastEpoch = DATime - quarterEpochTime;
+    const adjustedTimeLastEpoch = timeLastEpoch * (1 + (previousRetarget / 100));
+    const adjustedTimeSpan = diffSeconds + adjustedTimeLastEpoch;
+    adjustedTimeAvgSecs = adjustedTimeSpan / 503;
+    difficultyChange = (BLOCK_SECONDS_TARGET / (adjustedTimeSpan / 504) - 1) * 100;
+  } else {
     difficultyChange = (BLOCK_SECONDS_TARGET / (actualTimespan / (blocksInEpoch + 1)) - 1) * 100;
+  }
+
   // Max increase is x4 (+300%)
   if (difficultyChange > 300) {
     difficultyChange = 300;
@@ -126,7 +140,8 @@ export function calcDifficultyAdjustment(
   }
 
   const timeAvg = Math.floor(timeAvgSecs * 1000);
-  const remainingTime = remainingBlocks * timeAvg;
+  const adjustedTimeAvg = Math.floor(adjustedTimeAvgSecs * 1000);
+  const remainingTime = remainingBlocks * adjustedTimeAvg;
   const estimatedRetargetDate = remainingTime + nowSeconds * 1000;
 
   return {
@@ -139,6 +154,7 @@ export function calcDifficultyAdjustment(
     previousTime: DATime,
     nextRetargetHeight,
     timeAvg,
+    adjustedTimeAvg,
     timeOffset,
     expectedBlocks,
   };
@@ -155,9 +171,10 @@ class DifficultyAdjustmentApi {
       return null;
     }
     const nowSeconds = Math.floor(new Date().getTime() / 1000);
+    const quarterEpochBlockTime = blocks.getQuarterEpochBlockTime();
 
     return calcDifficultyAdjustment(
-      DATime, nowSeconds, blockHeight, previousRetarget,
+      DATime, quarterEpochBlockTime, nowSeconds, blockHeight, previousRetarget,
       config.MEMPOOL.NETWORK, latestBlock.timestamp
     );
   }

frontend/src/app/components/difficulty-mining/difficulty-mining.component.html

@@ -49,13 +49,15 @@
         <div class="item" *ngIf="showHalving">
           <h5 class="card-title" i18n="difficulty-box.next-halving">Next Halving</h5>
           <div class="card-text" i18n-ngbTooltip="mining.average-fee" [ngbTooltip]="halvingBlocksLeft" [tooltipContext]="{ epochData: epochData }" placement="bottom">
-            <span>{{ timeUntilHalving | date }}</span>
+            <ng-container *ngTemplateOutlet="epochData.blocksUntilHalving === 1 ? blocksSingular : blocksPlural; context: {$implicit: epochData.blocksUntilHalving }"></ng-container>
+            <ng-template #blocksPlural let-i i18n="shared.blocks">{{ i }} <span class="shared-block">blocks</span></ng-template>
+            <ng-template #blocksSingular let-i i18n="shared.block">{{ i }} <span class="shared-block">block</span></ng-template>
             <div class="symbol" *ngIf="blocksUntilHalving === 1; else approxTime">
-              <app-time kind="until" [time]="epochData.timeAvg + now" [fastRender]="false" [fixedRender]="true" [precision]="1" minUnit="minute"></app-time>
+              <app-time kind="until" [time]="epochData.adjustedTimeAvg + now" [fastRender]="false" [fixedRender]="true" [precision]="1" minUnit="minute"></app-time>
             </div>
             <ng-template #approxTime>
               <div class="symbol">
-                <app-time kind="until" [time]="timeUntilHalving" [fastRender]="false" [fixedRender]="true" [precision]="0" [numUnits]="2" [units]="['year', 'day', 'hour', 'minute']"></app-time>
+                <span>{{ timeUntilHalving | date }}</span>
               </div>
             </ng-template>
           </div>

frontend/src/app/components/difficulty-mining/difficulty-mining.component.ts

@@ -16,6 +16,7 @@ interface EpochProgress {
   blocksUntilHalving: number;
   timeUntilHalving: number;
   timeAvg: number;
+  adjustedTimeAvg: number;
 }
 
 @Component({
@@ -85,6 +86,7 @@ export class DifficultyMiningComponent implements OnInit {
           blocksUntilHalving: this.blocksUntilHalving,
           timeUntilHalving: this.timeUntilHalving,
           timeAvg: da.timeAvg,
+          adjustedTimeAvg: da.adjustedTimeAvg,
         };
         return data;
       })

frontend/src/app/components/difficulty/difficulty.component.ts

@@ -19,6 +19,7 @@ interface EpochProgress {
   blocksUntilHalving: number;
   timeUntilHalving: number;
   timeAvg: number;
+  adjustedTimeAvg: number;
 }
 
 type BlockStatus = 'mined' | 'behind' | 'ahead' | 'next' | 'remaining';
@@ -153,6 +154,7 @@ export class DifficultyComponent implements OnInit {
           blocksUntilHalving,
           timeUntilHalving,
           timeAvg: da.timeAvg,
+          adjustedTimeAvg: da.adjustedTimeAvg,
         };
         return data;
       })

frontend/src/app/components/mempool-blocks/mempool-blocks.component.html

@@ -34,7 +34,7 @@
                   <app-time kind="until" [time]="(1 * i) + now + 61000" [fastRender]="false" [fixedRender]="true" [precision]="1" minUnit="minute"></app-time>
                 </ng-template>
                 <ng-template #timeDiffMainnet>
-                  <app-time kind="until" [time]="da.timeAvg * (i + 1) + now + da.timeOffset" [fastRender]="false" [fixedRender]="true" [precision]="1" minUnit="minute"></app-time>
+                  <app-time kind="until" [time]="da.adjustedTimeAvg * (i + 1) + now + da.timeOffset" [fastRender]="false" [fixedRender]="true" [precision]="1" minUnit="minute"></app-time>
                 </ng-template>
               </div>
               <ng-template #mergedBlock>

frontend/src/app/components/transaction/transaction.component.html

@@ -133,7 +133,7 @@
                         </ng-template>
                         <ng-template #timeEstimateDefault>
                           <span class="eta justify-content-end" [class]="(acceleratorAvailable && accelerateCtaType === 'button') ? 'd-flex align-items-center' : ''">
-                            <app-time kind="until" *ngIf="(da$ | async) as da;" [time]="da.timeAvg * (this.mempoolPosition.block + 1) + now + da.timeOffset" [fastRender]="false" [fixedRender]="true"></app-time>
+                            <app-time kind="until" *ngIf="(da$ | async) as da;" [time]="da.adjustedTimeAvg * (this.mempoolPosition.block + 1) + now + da.timeOffset" [fastRender]="false" [fixedRender]="true"></app-time>
                             <a *ngIf="!tx.acceleration && acceleratorAvailable && accelerateCtaType === 'button' && !tx?.acceleration" [href]="'/services/accelerator/accelerate?txid=' + tx.txid" class="btn btn-sm accelerate btn-small-height" i18n="transaction.accelerate|Accelerate button label" (click)="onAccelerateClicked()">Accelerate</a>
                           </span>
                         </ng-template>

frontend/src/app/docs/api-docs/api-docs-data.ts

@@ -155,6 +155,7 @@ export const restApiDocsData = [
   previousRetarget: -4.807005268478962,
   nextRetargetHeight: 741888,
   timeAvg: 302328,
+  adjustedTimeAvg: 302328,
   timeOffset: 0
 }`
         },
@@ -171,6 +172,7 @@ export const restApiDocsData = [
   previousRetarget: -4.807005268478962,
   nextRetargetHeight: 741888,
   timeAvg: 302328,
+  adjustedTimeAvg: 302328,
   timeOffset: 0
 }`
         },
@@ -187,6 +189,7 @@ export const restApiDocsData = [
   previousRetarget: -4.807005268478962,
   nextRetargetHeight: 741888,
   timeAvg: 302328,
+  adjustedTimeAvg: 302328,
   timeOffset: 0
 }`
         },
@@ -203,6 +206,7 @@ export const restApiDocsData = [
   previousRetarget: -4.807005268478962,
   nextRetargetHeight: 741888,
   timeAvg: 302328,
+  adjustedTimeAvg: 302328,
   timeOffset: 0
 }`
         }

frontend/src/app/interfaces/node-api.interface.ts

@@ -54,6 +54,7 @@ export interface DifficultyAdjustment {
   previousTime: number;
   nextRetargetHeight: number;
   timeAvg: number;
+  adjustedTimeAvg: number;
   timeOffset: number;
   expectedBlocks: number;
 }