Add special case: Incineration

forum-network/src/classes/dao/forum.js

@@ -3,7 +3,7 @@ import { Action } from '../display/action.js';
 import { Actor } from '../display/actor.js';
 import params from '../../params.js';
 import { ReputationHolder } from '../reputation/reputation-holder.js';
-import { displayNumber, EPSILON } from '../../util.js';
+import { displayNumber, EPSILON, INCINERATOR_ADDRESS } from '../../util.js';
 
 const CITATION = 'citation';
 const BALANCE = 'balance';
@@ -70,9 +70,14 @@ export class Forum extends ReputationHolder {
   }
 
   async addPost(authorId, postContent) {
+    console.log('addPost', { authorId, postContent });
     const post = new Post(this, authorId, postContent);
     this.posts.addVertex(post.id, post, post.getLabel());
     for (const { postId: citedPostId, weight } of post.citations) {
+      // Special case: Incinerator
+      if (citedPostId === INCINERATOR_ADDRESS && !this.posts.getVertex(INCINERATOR_ADDRESS)) {
+        this.posts.addVertex(INCINERATOR_ADDRESS, { name: 'Incinerator' }, 'Incinerator');
+      }
       this.posts.addEdge(CITATION, post.id, citedPostId, weight);
     }
     return post;
@@ -171,22 +176,43 @@ export class Forum extends ReputationHolder {
       for (const citationEdge of citationEdges) {
         const { weight } = citationEdge;
         let outboundAmount = weight * increment;
+        if (Math.abs(outboundAmount) > EPSILON) {
           const balanceToOutbound = this.posts.getEdgeWeight(BALANCE, citationEdge.from, citationEdge.to) ?? 0;
+          let refundFromOutbound = 0;
+
+          // Special case: Incineration.
+          if (citationEdge.to.id === INCINERATOR_ADDRESS) {
+            // Only a positive amount may be incinerated! Otherwise the sink could be used as a source.
+            if (outboundAmount < 0) {
+              throw new Error('Incinerator can only receive positive citations!');
+            }
+            // Reputation sent to the incinerator is burned! This means it is deducted from the sender,
+            // without increasing the value of any other token.
+            this.actions.propagate.log(citationEdge.from.data, { name: 'Incinerator' }, `(${increment})`);
+          } else {
             // We need to ensure that we at most undo the prior effects of this post
             if (initialNegative) {
               outboundAmount = outboundAmount < 0
                 ? Math.max(outboundAmount, -balanceToOutbound)
                 : Math.min(outboundAmount, -balanceToOutbound);
             }
-        if (Math.abs(outboundAmount) > EPSILON) {
-          const refundFromOutbound = await this.propagateValue(citationEdge, {
+
+            // Recursively propagate reputation effects
+            refundFromOutbound = await this.propagateValue(citationEdge, {
               rewardsAccumulator,
               increment: outboundAmount,
               depth: depth + 1,
               initialNegative: initialNegative || (depth === 0 && outboundAmount < 0),
             });
 
+            // Any excess (negative) amount that could not be propagated,
+            // i.e. because a cited post has been reduced to zero value,
+            // is retained by the citing post.
             outboundAmount -= refundFromOutbound;
+          }
+
+          // Keep a record of the effect of the reputation transferred along this edge in the graph,
+          // so that later, negative citations can be constrained to at most undo these effects.
           this.posts.setEdgeWeight(BALANCE, citationEdge.from, citationEdge.to, balanceToOutbound + outboundAmount);
           totalOutboundAmount += outboundAmount;
 

forum-network/src/index.html

@@ -22,6 +22,7 @@
       <li><a href="./tests/forum5.test.html">Destroy a post after it has received positive citations</a></li>
       <li><a href="./tests/forum6.test.html">Initially zero-valued posts later receive citations</a></li>
       <li><a href="./tests/forum7.test.html">Negatively cite a zero-valued post</a></li>
+      <li><a href="./tests/forum8.test.html">Incinerate reputation</a></li>
     </ol>
   </ul>
   <ul>

forum-network/src/tests/all.test.html

@@ -34,6 +34,7 @@
 <script type="module" src="./scripts/forum/forum5.test.js"></script>
 <script type="module" src="./scripts/forum/forum6.test.js"></script>
 <script type="module" src="./scripts/forum/forum7.test.js"></script>
+<script type="module" src="./scripts/forum/forum8.test.js"></script>
 <script defer class="mocha-init">
   mocha.setup({
     ui: 'bdd',

forum-network/src/tests/forum8.test.html

@@ -0,0 +1,26 @@
+<!DOCTYPE html>
+
+<head>
+  <title>Forum test 8</title>
+  <meta name="viewport" content="width=device-width, initial-scale=1.0" />
+  <link rel="stylesheet" href="https://unpkg.com/mocha/mocha.css" />
+  <link type="text/css" rel="stylesheet" href="../index.css" />
+</head>
+
+<body>
+  <h2><a href="../">DGF Tests</a></h2>
+  <div id="mocha"></div>
+  <div id="scene"></div>
+</body>
+<script src="https://cdnjs.cloudflare.com/ajax/libs/radash/10.7.0/radash.js"
+  integrity="sha512-S207zKWG3iqXqe6msO7/Mr8X3DzzF4u8meFlokHjGtBPTGUhgzVo0lpcqEy0GoiMUdcoct+H+SqzoLsxXbynzg=="
+  crossorigin="anonymous" referrerpolicy="no-referrer"></script>
+<script src="https://unpkg.com/mocha/mocha.js"></script>
+<script src="https://unpkg.com/chai/chai.js"></script>
+<script type="module" src="./scripts/forum/forum8.test.js"></script>
+<script defer class="mocha-init">
+  mocha.setup({
+    ui: 'bdd',
+  });
+  chai.should();
+</script>

forum-network/src/tests/scripts/forum/forum8.test.js

@@ -0,0 +1,40 @@
+import { INCINERATOR_ADDRESS, mochaRun } from '../../../util.js';
+import { ForumTest } from './forum.test-util.js';
+
+describe('Forum', function tests() {
+  this.timeout(0);
+
+  const forumTest = new ForumTest();
+
+  before(async () => {
+    await forumTest.setup();
+  });
+
+  context('Incinerate reputation', async () => {
+    let forum;
+    let experts;
+    let posts;
+
+    before(() => {
+      forum = forumTest.forum;
+      experts = forumTest.experts;
+      posts = forumTest.posts;
+    });
+
+    it('Post1', async () => {
+      await forumTest.addPost(experts[0], 10);
+      forum.getPost(posts[0]).value.should.equal(10);
+    });
+
+    it('Post2 burns reputation from Post1', async () => {
+      await forumTest.addPost(experts[0], 10, [
+        { postId: posts[0], weight: -1 },
+        { postId: INCINERATOR_ADDRESS, weight: 1 },
+      ]);
+      forum.getPost(posts[0]).value.should.equal(0);
+      forum.getPost(posts[1]).value.should.equal(0);
+    });
+  });
+});
+
+mochaRun();

forum-network/src/util.js

@@ -4,6 +4,8 @@ const timers = new Map();
 
 export const EPSILON = 2.23e-16;
 
+export const INCINERATOR_ADDRESS = 0;
+
 export const debounce = async (fn, delayMs) => {
   const timer = timers.get(fn);
   if (timer) {