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R85 · Travelling salesman improved by 2-opt

blind round 5/8 local models answered

Answers below are anonymized and shuffled. Read, judge, pick a favourite — then scroll down and reveal the models.

The field: deepseek-r1:14b · gemma4:26b · llama3.1:8b · mistral-small:24b · qwen3-coder:30b · qwen3:14b · qwen3:8b · qwen3.5:9b — listed alphabetically, which is not the order of the cards below.

2 of the 8 local models delivered nothing through our test harness in this round — for reasons that lie with our setup, not with the models. Those cards are marked DNF like any other, but they are not evidence about those models. Which ones, and why, is spelled out in the reveal.

Show task
Create ONE self-contained HTML file (STRICT LIMIT: max 7000 characters in total — this is a budget on characters, not on lines, so removing line breaks does not help) that animates a travelling-salesman tour over 60 random cities on a <canvas>. Start from a nearest-neighbour tour, then repeatedly apply 2-opt: highlight the two edges being tested, and when a swap shortens the tour, redraw the reversed segment so the crossing visibly untangles. Show the current tour length and the number of improvements made. Smooth requestAnimationFrame animation, NO user input, starts immediately and keeps running (restart with a fresh random instance when finished). No external libraries, no comments needed. Output ONLY the HTML file content, nothing else.

The answers — blind

Local models (Brain cluster) — identical prompt, anonymized order
No usable answer reached the harness (TIMEOUT). Counted as a did-not-finish.
MODEL Bqwen3-coder:30bBLANKLIMFORMAT
Show code
```html
<!DOCTYPE html>
<html><head><title>2-Opt TSP Animation</title></head><body style="background:#111;display:flex;justify-content:center;align-items:center;height:100vh;margin:0;"><canvas id="c" width="800" height="600" style="border:1px solid #333;"></canvas><div id="info" style="position:absolute;top:20px;left:20px;color:#ccc;font-family:monospace;">Length: 0.00 | Improvements: 0</div><script>
const c = document.getElementById('c');
const ctx = c.getContext('2d');
let cities = [];
let tour = [];
let bestTour = [];
let improvementCount = 0;
let animationRunning = true;

const CANVAS_W = c.width;
const CANVAS_H = c.height;
const N_CITIES = 60; // Target number of cities

function dist(p1, p2) {
    return Math.sqrt((p1.x - p2.x)**2 + (p1.y - p2.y)**2);
}

function generateCities() {
    cities = [];
    for (let i = 0; i < N_CITIES; i++) {
        cities.push({ x: Math.random() * CANVAS_W, y: Math.random() * CANVAS_H });
    }
}

function calculateTourLength(t) {
    let length = 0;
    for (let i = 0; i < t.length; i++) {
        const p1 = cities[t[i]];
        const p2 = cities[t[(i + 1) % t.length]];
        length += dist(p1, p2);
    }
    return length;
}

function nearestNeighborTour() {
    let current = 0;
    let newTour = [current];
    const visited = new Set([current]);

    for (let i = 1; i < N_CITIES; i++) {
        let nearestIndex = -1;
        let minD = Infinity;

        for (let j = 0; j < N_CITIES; j++) {
            if (!visited.has(j)) {
                const d = dist(cities[current], cities[j]);
                if (d < minD) {
                    minD = d;
                    nearestIndex = j;
                }
            }
        }

        newTour.push(nearestIndex);
        visited.add(nearestIndex);
        current = nearestIndex;
    }
    return newTour;
}

function initializeTSP() {
    generateCities();
    tour = nearestNeighborTour();
    bestTour = [...tour];
    improvementCount = 0;
    updateInfoDisplay();
    drawCanvas(true); // Initial clear draw
}

function updateInfoDisplay() {
    const infoDiv = document.getElementById('info');
    infoDiv.innerHTML = `Length: ${currentLength.toFixed(2)} | Improvements: ${improvementCount}`;
}

let currentLength = 0;
let bestLength = Infinity;

// Drawing function (optimized for performance)
function drawCanvas(highlightEdges = [], tempTour = null, isInitial = false) {
    ctx.clearRect(0, 0, CANVAS_W, CANVAS_H);
    ctx.lineWidth = 2;

    // Draw all cities
    cities.forEach(c => {
        ctx.beginPath();
        ctx.arc(c.x, c.y, 4, 0, Math.PI * 2);
        ctx.fillStyle = '#aaa';
        ctx.fill();
    });

    // Draw current best tour (faintly)
    if (!isInitial && bestTour.length > 0) {
        ctx.strokeStyle = 'rgba(150, 150, 255, 0.3)';
        ctx.beginPath();
        for (let i = 0; i < N_CITIES; i++) {
            const p1 = cities[bestTour[i]];
            const p2 = cities[bestTour[(i + 1) % N_CITIES]];
            if (i === 0) ctx.moveTo(p1.x, p1.y);
            else ctx.lineTo(p1.x, p1.y);
        }
        ctx.stroke();
    }

    // Draw the current tour/segment
    let drawTour = tempTour || [...tour];
    if (drawTour.length === 0) return;
    
    for (let i = 0; i < N_CITIES; i++) {
        const p1 = cities[drawTour[i]];
        const p2 = cities[drawTour[(i + 1) % N_CITIES]];

        // Check if this edge needs highlighting
        const isHighlighted = highlightEdges.some(e => (Math.abs(e.start - i) < 1 && Math.abs(e.end - ((i + 1) % N_CITIES)) < 1));
        
        ctx.strokeStyle = isHighlighted ? '#ff4500' : (i === 0 ? '#ccc' : '#666');
        ctx.globalAlpha = isHighlighted ? 1.0 : 0.8;

        ctx.beginPath();
        ctx.moveTo(p1.x, p1.y);
        ctx.lineTo(p2.x, p2.y);
        ctx.stroke();
    }
    ctx.globalAlpha = 1.0;
}


// Main 2-Opt Improvement Loop
async function runTwoOpt() {
    if (!animationRunning) return;

    let improvedInCycle = false;
    let bestImprovement = 0;
    let bestSwap = null;
    let initialTourLength = currentLength;

    for (let i = 0; i < N_CITIES; i++) {
        for (let j = i + 2; j < N_CITIES; j++) {
            // Check for edge overlap/adjacency constraint (i and j+1 are the endpoints)
            if ((i === 0 && j === N_CITIES - 1)) continue;

            const pAIndex = tour[i];
            const pBIndex = tour[(i + 1) % N_CITIES]; // Edge 1: A -> B
            const pCIndex = tour[j];
            const pDIndex = tour[(j + 1) % N_CITIES]; // Edge 2: C -> D

            // The two edges being tested are (A->B) and (C->D).
            // Swapping reverses the segment B...C. New path: A -> C ... D -> B.
            
            const currentDist = dist(cities[pAIndex], cities[pBIndex]) + dist(cities[pCIndex], cities[pDIndex]);
            
            // Calculate cross-over length (A->C) + (B->D)
            let newDist;
            if ((i === 0 && j < N_CITIES - 1)) { // Case: Closing the loop handles indices correctly
                newDist = dist(cities[pAIndex], cities[pCIndex]) + dist(cities[pBIndex], cities[pDIndex]);
            } else {
                 // General case assuming linear segment for simplicity in quick code structure, need to handle wrap-around carefully.
                 // Since we iterate i < j and the tour is cyclic, we simplify the indices based on the standard 2-opt definition: swap edges (i, i+1) and (j, j+1).
                const pA = cities[tour[i]];
                const pB = cities[tour[(i + 1) % N_CITIES]];
                const pC = cities[tour[j]];
                const pD = cities[tour[(j + 1) % N_CITIES]];

                // For simplicity and speed, let's use the standard index approach: swap edges i->i+1 and j->j+1.
                newDist = dist(cities[tour[i]], cities[tour[j]]) + dist(cities[tour[(i + 1) % N_CITIES]], cities[tour[(j + 1) % N_CITIES]]);
            }


            const improvement = currentDist - newDist;

            if (improvement > bestImprovement && improvement > 0.01) {
                bestImprovement = improvement;
                bestSwap = { i: i, j: j }; // Store indices for the swap
            }
        }
    }

    // --- Visualization & Execution ---

    if (!bestSwap || bestImprovement < 0.01) {
        currentLength = calculateTourLength(tour);
        updateInfoDisplay();
        drawCanvas([]); // No highlighting
        improvementCount++; // Fake increment if no change, to prevent infinite loop on flat terrain (though it shouldn't happen often enough).

        // If we finished or improvement is minimal, pause and restart/exit.
        if (!improvedInCycle && bestImprovement < 0.01) {
            setTimeout(() => {
                console.log("Optimization converged.");
                bestLength = currentLength;
                animationRunning = false; // Stop the loop for now
            }, 500);
        } else {
             // If we didn't find a swap but haven't reached convergence, just redraw and wait.
             setTimeout(() => requestAnimationFrame(runTwoOpt), 100);
        }
        return;
    }

    improvedInCycle = true;
    bestLength = Math.min(bestLength === Infinity ? currentLength : bestLength, calculateTourLength(tour) - bestImprovement);

    // 1. Highlight tested edges (i -> i+1 and j -> j+1)
    const highlight = [];
    highlight.push({start: bestSwap.i, end: (bestSwap.i + 1) % N_CITIES});
    highlight.push({start: bestSwap.j, end: (bestSwap.j + 1) % N_CITIES});

    // 2. Visualize the swap transition (The actual complex part - drawing the reversed segment)
    const newTour = [...tour];
    const startSegment = Math.min(bestSwap.i + 1, bestSwap.j); // Index after first edge
    const endSegment = Math.max(bestSwap.i, bestSwap.j);

    // Reverse the segment from index i+1 to j (inclusive)
    let reversedSegment = [];
    for (let k = startSegment; k <= endSegment; k++) {
        reversedSegment.push(newTour[k]);
    }
    reversedSegment.reverse(); // This is indices B...C, now C...B

    // Apply the swap: T' = T[0...i] + reverse(T[i+1...j]) + T[j+1...]
    let temp = [];
    for (let k = 0; k <= bestSwap.i; k++) {
        temp.push(newTour[k]); // Keep T[0...i]
    }
    temp.push(...reversedSegment); // Insert reversed segment
    for (let k = bestSwap.j + 1; k < N_CITIES; k++) {
        // This assumes a linear array model, which is fine if we map the indices correctly.
        // Given the complexity of handling cyclic indices in JS arrays for reversal, we will simply replace the segment B...C with C...B based on index list manipulation.
    }

    // Simple replacement: [0..i] + reverse(T[i+1..j]) + [j+1..N-1]
    let newTourSimple = [...tour];
    let segmentToReverse = [];
    for (let k = bestSwap.i + 1; k <= bestSwap.j; k++) {
        segmentToReverse.push(newTour[k]);
    }
    segmentToReverse.reverse();

    // Overwrite
MODEL Cdeepseek-r1:14bBLANKFORMAT
Show code
```html
<!DOCTYPE html>
<html><head><title>TSP Animation</title><style>canvas{border:1px solid black}</style></head>
<body><h1 style="color:#00f">Traveling Salesman</h1><canvas id=c id=mainCanvas width=800 height=600></canvas><div id=s stats></div>
<script>
const canvas=document.getElementById('c'), ctx=canvas.getContext('2d');
const W=canvas.width, H=canvas.height;
let cities, path, dist, cstat, animating, loops;

class City{constructor(){this.x=Math.random()*W; this.y=Math.random()*H;}

distance(c){return Math.hypot(this.x-c.x,this.y-c.y)}

color(){return `hsl(${Math.random()*360},100%,50%)`}}

function init(){cities=[]; for(let i=0;i<60;i++) cities.push(new City());}

let nearestNeighborTour=(()=>{
  const tour=[], visited=new Set;
  let start=cities[Math.floor(Math.random() * cities.length)];
  while(tour.length < 60){
    let next=start;
    for(let c of cities) if(!visited.has(c)){
      if(next===start&&!tour.length) next=c; else if(dist(start,c)<dist(start,next)) next=c;
    }
    tour.push(next); visited.add(next); start=next;
  } return {path:tour, dist:tour.reduce((sum,[a,b])=>sum+dist(a,b),0)};
})();

function reversePath(a,b){return [...Array(b-a+1)].map((_,i)=>path[a+i]||path[path.length - (a+i)]);}

let twoOpt=(()=>{
  let improved=0, best=Infinity;
  while(true){
    let i,j,minImprovement=-1;
    for(let a=0;a<path.length-2;a++)for(let b=a+2;b<path.length;b++){
      const d1=dist(path[a],path[a+1])+dist(path[b-1],path[b]);
      const d2=dist(path[a],path[b-1])+dist(path[a+1],path[b]);
      if(d2<d1 && (d1-d2>minImprovement)){
        minImprovement=d1-d2;
        i=a;j=b-1;
      }
    }if(minImprovement<0)break;if(minImprovement>0){
      const oldPath=path[i+1,...path.slice(i+1,j)], newPath=rever
```
MODEL Dqwen3:8bDNF
No usable answer reached the harness (THIN). Counted as a did-not-finish.
MODEL Eqwen3.5:9bBLANKFORMAT
Show code
```html
<!DOCTYPE html>
<html>
<head>
<title>TSP 2-Opt Optimization</title>
<style>
    body { background: #111; display: flex; justify-content: center; align-items: center; height: 100vh; margin: 0; font-family: sans-serif; color: white; }
    canvas { border: 1px solid #333; background: #000; }
    #info { position: absolute; bottom: 20px; left: 50%; transform: translateX(-50%); color: #ccc; font-size: 1.2em; }
</style>
</head>
<body>

<canvas id="tspCanvas" width="800" height="600"></canvas>
<div id="info">Length: 0 | Improvements: 0</div>

<script>
    const canvas = document.getElementById('tspCanvas');
    const ctx = canvas.getContext('2d');
    const infoDiv = document.getElementById('info');

    let points = [];
    let tourPathIndices = []; // Stores the indices of cities in order
    let currentLength = 0;
    let improvementsCount = 0;
    let isOptimizingPass = false;
    let animationStartTime = 0;
    const MAX_ITERATIONS = 15;

    // --- Utility Functions ---

    function distance(p1, p2) {
        return Math.sqrt((p1.x - p2.x)**2 + (p1.y - p2.y)**2);
    }

    function generatePoints() {
        points = [];
        const count = 60;
        for (let i = 0; i < count; i++) {
            points.push({
                x: Math.random() * canvas.width,
                y: Math.random() * canvas.height
            });
        }
    }

    function updateInfo(length) {
        infoDiv.innerHTML = `Length: ${length.toFixed(2)} | Improvements: ${improvementsCount}`;
    }

    // --- Visualization Functions ---

    function drawTour(pathIndices, highlightEdges = []) {
        ctx.clearRect(0, 0, canvas.width, canvas.height);

        // Draw all cities
        points.forEach(p => {
            ctx.beginPath();
            ctx.arc(p.x, p.y, 3, 0, Math.PI * 2);
            ctx.fillStyle = '#4CAF50';
            ctx.fill();
        });

        // Draw tour lines
        for (let i = 0; i < pathIndices.length; i++) {
            const p1Index = pathIndices[i];
            const p2Index = pathIndices[(i + 1) % pathIndices.length]; // Loop back to start
            
            let isHighlighted = false;
            for (const edges of highlightEdges) {
                // Check if the current segment matches a tested edge pair
                if ((p1Index === edges[0] && p2Index === edges[1]) || 
                    (p1Index === edges[1] && p2Index === edges[0])) {
                    isHighlighted = true;
                    break;
                }
            }

            ctx.beginPath();
            ctx.moveTo(points[p1Index].x, points[p1Index].y);
            ctx.lineTo(points[p2Index].x, points[p2Index].y);
            ctx.strokeStyle = isHighlighted ? '#FFEB3B' : '#607D8B';
            ctx.lineWidth = 1.5;
            ctx.stroke();
        }

        // Highlight the start/end point (for clarity)
        const startIndex = pathIndices[0];
        ctx.beginPath();
        ctx.arc(points[startIndex].x, points[startIndex].y, 6, 0, Math.PI * 2);
        ctx.fillStyle = 'yellow';
        ctx.fill();
    }

    // --- Optimization Algorithms ---

    function calculateInitialTour() {
        // Nearest Neighbor heuristic
        let currentCityIndex = 0;
        tourPathIndices = [currentCityIndex];
        const visited = new Array(points.length).fill(false);
        visited[currentCityIndex] = true;

        for (let count = 1; count < points.length; count++) {
            let nearestNeighborIndex = -1;
            let minDist = Infinity;
            
            for (let i = 0; i < points.length; i++) {
                if (!visited[i]) {
                    const dist = distance(points[currentCityIndex], points[i]);
                    if (dist < minDist) {
                        minDist = dist;
                        nearestNeighborIndex = i;
                    }
                }
            }

            tourPathIndices.push(nearestNeighborIndex);
            visited[nearestNeighborIndex] = true;
            currentCityIndex = nearestNeighborIndex;
        }
    }

    function calculateTourLength() {
        let length = 0;
        for (let i = 0; i < tourPathIndices.length; i++) {
            const p1Index = tourPathIndices[i];
            const p2Index = tourPathIndices[(i + 1) % tourPathIndices.length]; // Loop back
            length += distance(points[p1Index], points[p2Index]);
        }
        return length;
    }

    function applyTwoOptSwap(i, j) {
        // Swaps edges (i-1, i) and (j, j+1) to (i-1, j) and (i, j+1)
        if (Math.abs(i - j) < 2 || i === j) return false;

        let newPath = [];
        // Keep segment 0 until i-1
        for (let k = 0; k <= Math.min(i, j); k++) {
            newPath.push(tourPathIndices[k]);
        }
        // Reverse segment i to j
        const startReverse = Math.min(i, j);
        const endReverse = Math.max(i, j);
        for (let k = endReverse; k >= startReverse; k--) {
            newPath.push(tourPathIndices[k]);
        }
        // Keep segment j+1 until end
        for (let k = Math.min(i, j) + 1; k < tourPathIndices.length; k++) {
             if (!isNaN(parseInt(tourPathIndices[k]))) newPath.push(tourPathIndices[k]);
        }

        // Note: Due to the complexity of path indices and wrapping around, we simplify by just reversing the necessary segment within the array structure.
        let oldPath = [...tourPathIndices];
        
        // Simple reversal logic (assuming i < j): Reverse elements from index i up to j inclusive
        let newTour = [
            ...oldPath.slice(0, Math.min(i, j)),
            ...oldPath.slice(Math.min(i, j), Math.max(i, j) + 1).reverse(),
            ...oldPath.slice(Math.max(i, j) + 1)
        ];

        let newLength = calculateTourLengthFromPath(newTour);
        return { success: true, newPath: newTour, lengthDifference: newLength - currentLength };
    }

    function calculateTourLengthFromPath(path) {
         let length = 0;
         for (let i = 0; i < path.length; i++) {
            const p1Index = path[i];
            const p2Index = path[(i + 1) % path.length]; 
            length += distance(points[p1Index], points[p2Index]);
        }
        return length;
    }


    // --- Main Loop & State Machine ---

    let optimizationAttemptCount = 0;

    function findImprovement() {
        if (optimizationAttemptCount++ > MAX_ITERATIONS) return null;
        
        const N = points.length;
        
        for (let i = 1; i < N - 2; i++) { // Start at index 1, cannot swap last two edges
            for (let j = i + 1; j < N - 1; j++) {
                // Test swapping segments [i-1, i] and [j, j+1]
                
                // Create a temporary path for testing the swap: reverse segment i to j
                let testPath = [...tourPathIndices];
                let swappedSegment = testPath.slice(i, j + 1).reverse();
MODEL Fqwen3:14bBLANKLIMFORMAT
Show code
```html
<!DOCTYPE html>
<html>
<head>
<title>2-Opt TSP Optimization</title>
<style>body {margin:0;overflow:hidden;}canvas {display:block;background:#111;}</style>
</head>
<body>
<canvas id="tspCanvas"></canvas>
<script>
const canvas = document.getElementById('tspCanvas');
const ctx = canvas.getContext('2d');

// Set canvas size based on screen dimensions for better viewing experience
let W, H;
function resize() {
    W = window.innerWidth;
    H = window.innerHeight;
    canvas.width = W * 0.95;
    canvas.height = H * 0.85;
}
window.addEventListener('resize', resize);
resize();

const NUM_CITIES = 60;
let cities = [];
let tour = [];
let currentLength = 0;
let improvements = 0;

// Helper function for distance squared (avoids Math.sqrt until necessary)
function distSq(p1, p2) {
    return (p1[0] - p2[0])**2 + (p1[1] - p2[1])**2;
}

// Calculate Euclidean distance
function dist(p1, p2) {
    return Math.sqrt(distSq(p1, p2));
}

// Function to generate random cities
function generateCities() {
    cities = [];
    for (let i = 0; i < NUM_CITIES; i++) {
        cities.push([Math.random() * W * 0.8 + W * 0.1, Math.random() * H * 0.8 + H * 0.1]);
    }
}

// Nearest Neighbor heuristic for initial tour
function nearestNeighbor() {
    tour = [];
    const visited = new Set();
    let currentCityIndex = 0; // Start at city 0
    tour.push(currentCityIndex);
    visited.add(currentCityIndex);

    for (let i = 1; i < NUM_CITIES; i++) {
        let nearestIndex = -1;
        let minD = Infinity;

        for (let j = 0; j < NUM_CITIES; j++) {
            if (!visited.has(j)) {
                const d = dist(cities[tour[i - 1]], cities[j]);
                if (d < minD) {
                    minD = d;
                    nearestIndex = j;
                }
            }
        }

        if (nearestIndex !== -1) {
            tour.push(nearestIndex);
            visited.add(nearestIndex);
        }
    }
    // Complete the circuit by returning to the start (city 0)
    currentLength = calculateTourLength();
}

function calculateTourLength() {
    let totalDist = 0;
    for (let i = 0; i < tour.length - 1; i++) {
        totalDist += dist(cities[tour[i]], cities[tour[i+1]]);
    }
    // Close the loop: last city to starting city
    totalDist += dist(cities[tour[tour.length - 1]], cities[tour[0]]);
    return totalDist;
}

/**
 * Implements a single 2-opt swap and checks for improvement.
 * @param {number} i Start index of the first edge (A -> B)
 * @param {number} j End index of the second edge (C -> D)
 * @returns {boolean} True if an improvement was found and applied.
 */
function tryTwoOpt(i, j) {
    // Indices must be valid and non-adjacent for a proper swap (i+1 < j)
    if (i >= j || i < 0 || j >= tour.length - 1) return false;

    const A = cities[tour[i]];     // City before first cut
    const B = cities[tour[i + 1]]; // City after first cut
    const C = cities[tour[j]];     // City before second cut
    const D = cities[tour[j + 1]]; // City after second cut

    const oldLength = dist(A, B) + dist(C, D);
    const newLength = dist(A, C) + dist(B, D);

    if (newLength < oldLength - 0.1) { // Use tolerance for floating point comparison
        // Improvement found! Swap the segment [i+1, j]
        for (let k = i + 1; k <= j; k++) {
            tour[k] = tour[k - 1];
        }
        tour[i + 1] = tour[j]; // This assignment is technically wrong for a simple shift. We need reversal logic.

        // Correct Reversal Logic: Reverse the segment from index i+1 up to j
        const start = i + 1;
        const end = j;
        while (start < Math.floor((start + end) / 2)) {
            const mid = Math.floor((start + end) / 2);
            const mirror = start + end - mid;
            [tour[start], tour[mirror]] = [tour[mirror], tour[start]];
            start++;
            end--;
        }

        // Update the length and state
        currentLength = currentLength - (dist(A, B) + dist(C, D)) + newLength;
        improvements++;
        return true;
    }
    return false;
}


function draw() {
    ctx.clearRect(0, 0, W, H);

    // Draw all cities
    ctx.fillStyle = '#fff';
    for (let i = 0; i < NUM_CITIES; i++) {
        ctx.beginPath();
        ctx.arc(cities[i][0], cities[i][1], 5, 0, Math.PI * 2);
        ctx.fill();
    }

    // Draw the tour lines (background)
    ctx.strokeStyle = '#333';
    ctx.lineWidth = 1;
    for (let i = 0; i < NUM_CITIES; i++) {
        const p1 = cities[tour[i]];
        const p2 = cities[tour[(i + 1) % NUM_CITIES]];
        ctx.beginPath();
        ctx.moveTo(p1[0], p1[1]);
        ctx.lineTo(p2[0], p2[1]);
        ctx.stroke();
    }

    // Draw current optimization info
    ctx.fillStyle = '#fff';
    ctx.font = '18px monospace';
    const statsDiv = document.createElement('div');
    statsDiv.style.position = 'absolute';
    statsDiv.style.top = '10px';
    statsDiv.style.left = '10px';
    statsDiv.innerHTML = `Tour Length: ${currentLength.toFixed(2)} | Improvements: ${improvements}`;
    document.body.appendChild(statsDiv);

    requestAnimationFrame(draw);
}


// --- Main Animation Loop and State Management ---

let animationState = {
    active: false,
    iteration: 0,
    swap_i: -1, // i for edge (i, i+1)
    swap_j: -1  // j for edge (j, j+1)
};

function findNextImprovement() {
    let bestI = -1;
    let bestJ = -1;
    let maxImprovement = 0;

    // Optimization search loop: Iterate over all pairs i and j such that i < j-1
    for (let i = 0; i < NUM_CITIES - 2; i++) {
        for (let j = i + 2; j < NUM_CITIES - 1; j++) {
            // Temporarily store current state to check the potential gain without modifying 'tour'
            const originalTour = [...tour];
            const tempImprovements = improvements;
            const tempLength = currentLength;

            // Simulate the swap (this requires a clean copy of the tour)
            let simulatedCities = JSON.parse(JSON.stringify(originalTour));
            
            // Reversal logic for simulation
            const start = i + 1;
            const end = j;
            while (start < Math.floor((start + end) / 2)) {
                const mid = Math.floor((start + end) / 2);
                const mirror = start + end - mid;
                [simulatedCities[start], simulatedCities[mirror]] = [simulatedCities[mirror], simulatedCities[start]];
                start++;
                end--;
            }

            // Calculate the length difference for this potential swap
            const A_s = cities[originalTour[i]];
            const B_s = cities[originalTour[i + 1]];
            const C_s = cities[originalTour[j]];
            const D_s = cities[originalTour[j + 1]];

            const oldL = dist(A_s, B_s) + dist(C_s, D_s);
            const newL = dist(A_s, C_s) + dist(B_s, D_s);
            const improvement = oldL - newL;

            if (improvement > maxImprovement && improvement > 0.1) {
                maxImprovement = improvement;
                bestI = i;
                bestJ = j;
            }
        }
    }
    return { i: bestI, j: bestJ, improve: maxImprovement };
}

function animateOptimization(deltaTime) {
    // 1. Find the optimal swap (must be done outside the animation loop for performance)
    const bestSwap = findNextImprovement();

    if (!bestSwap.i) {
        // No more improvements possible or found in this pass
        console.log("Optimal solution reached.");
        return true; // Signal completion
    }

    animationState.swap_i = bestSwap.i;
    animationState.swap_j = bestSwap.j;
    animationState.active = true;

    // 2. Perform the swap and update state immediately (this is complex, so we skip frame-by-frame visual animation for simplicity and focus on convergence)
    // Instead of animating the segment reversal, we apply the change instantly upon detection to maintain smoothness and rapid convergence feel.
    const i = bestSwap.i;
    const j = bestSwap.j;

    // Apply Reversal Logic: Reverse the segment from index i+1 up to j
    const start = i + 1;
    const end = j;
    while (start < Math.floor((start + end) / 2)) {
        const mid = Math.floor((start + end) / 2);
        const mirror = start + end - mid;
        [tour[start], tour[mirror]] = [tour[mirror], tour[start]];
        start++;
        end--;
    }

    // Update length and improvements on successful swap
    currentLength -= (dist(cities[tour[i]], cities[tour[i+1]]) + dist(cities[tour[j]], cities[tour[j+1]]));
    currentLength += (dist(cities[tour[i]], cities[tour[j]]) + dist(cities[tour[i+1]], cities[tour[j+1]]));
    improvements++;

    // Continue the process immediately to find the next improvement
    return false; // Not finished
}


function mainLoop(timestamp) {
    const deltaTime = timestamp - (mainLoop.lastTime || timestamp);
    mainLoop.lastTime = timestamp
MODEL Gllama3.1:8bERRSTATFORMAT
Show code
```html
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Travelling Salesman Tour</title>
    <style>
        body {
            margin: 0;
            background-color: #f0f0f0;
        }
        canvas {
            border: 1px solid black;
        }
    </style>
</head>
<body>
<script>
    const cities = [];
    for (let i = 0; i < 60; i++) {
        cities.push({x: Math.random() * 800, y: Math.random() * 600});
    }

    let tour = [...cities.keys()];
    let shortestTour = [...tour];
    let improvementsCount = 0;
    const canvas = document.createElement('canvas');
    document.body.appendChild(canvas);
    canvas.width = 800;
    canvas.height = 600;

    const ctx = canvas.getContext('2d');

    function nearestNeighbour() {
        tour = [0];
        for (let i = 1; i < cities.length - 1; i++) {
            let minDist = Infinity, argMinDist = null;
            for (let j = 0; j < cities.length; j++) {
                if (!tour.includes(j)) {
                    const dist = Math.hypot(cities[tour[i - 1]].x - cities[j].x, cities[tour[i - 1]].y - cities[j].y);
                    if (dist < minDist) {
                        minDist = dist;
                        argMinDist = j;
                    }
                }
            }
            tour.push(argMinDist);
        }
    }

    function twoOpt() {
        let improved = false;
        for (let i = 1; i < tour.length - 2; i++) {
            for (let j = i + 1; j < tour.length - 1; j++) {
                if (j - i > Math.abs(tour[j] - tour[i]) && !tour.slice(i, j).includes(tour[j])) {
                    ctx.clearRect(0, 0, canvas.width, canvas.height);
                    for (let k = 0; k < tour.length; k++) {
                        const x1 = cities[tour[k]].x;
                        const y1 = cities[tour[k]].y;
                        const x2 = cities[tour[(k + 1) % tour.length]].x;
                        const y2 = cities[tour[(k + 1) % tour.length]].y;
                        ctx.beginPath();
                        ctx.moveTo(x1, y1);
                        ctx.lineTo(x2, y2);
                        ctx.stroke();
                    }
                    for (let k = i; k < j; k++) {
                        ctx.beginPath();
                        ctx.arc(cities[tour[k]].x, cities[tour[k]].y, 3, 0, 2 * Math.PI);
                        ctx.fill();
                    }
                    ctx.beginPath();
                    ctx.moveTo(cities[tour[i]].x, cities[tour[i]].y);
                    ctx.lineTo(cities[tour[j]].x, cities[tour[j]].y);
                    ctx.stroke();

                    const newTour = [...tour.slice(0, i), ...tour.slice(i, j).reverse(), ...tour.slice(j)];
                    let newLength = 0;
                    for (let k = 0; k < newTour.length - 1; k++) {
                        newLength += Math.hypot(cities[newTour[k]].x - cities[newTour[k + 1]].x, cities[newTour[k]].y - cities[newTour[k + 1]].y);
                    }
                    if (newLength < tour.length) {
                        improved = true;
                        shortestTour = [...tour];
                        improvementsCount++;
                        tour = newTour.slice();
                    } else {
                        ctx.beginPath();
                        ctx.moveTo(cities[tour[i]].x, cities[tour[i]].y);
                        ctx.lineTo(cities[tour[j]].x, cities[tour[j]].y);
                        ctx.stroke();

                        const x1_2 = cities[newtour[i]].x;
                        const y1_2 = cities[newtour[i]].y;
                        const x2_2 = cities[newtour[(i + 1) % tour.length]].x;
                        const y2_2 = cities[newtour[(i + 1) % tour.length]].y;

                        ctx.beginPath();
                        ctx.moveTo(x1_2, y1_2);
                        ctx.lineTo(x2_2, y2_2);
                        ctx.stroke();

                        const x1_3 = cities[tour[i]].x;
                        const y1_3 = cities[tour[i]].y;
                        const x2_3 = cities[tour[j]].x;
                        const y2_3 = cities[tour[j]].y;

                        ctx.beginPath();
                        ctx.moveTo(x1_3, y1_3);
                        ctx.lineTo(x2_3, y2_3);
                        ctx.stroke();

                        ctx.beginPath();
                        ctx.arc(cities[newtour[i]].x, cities[newtour[i]].y, 3, 0, 2 * Math.PI);
                        ctx.fill();

                        ctx.beginPath();
                        ctx.arc(cities[tour[i]].x, cities[tour[i]].y, 3, 0, 2 * Math.PI);
                        ctx.fill();
                    }
                }
            }
        }

        if (improved) {
            requestAnimationFrame(twoOpt);
        } else {
            document.title = `Tour length: ${tour.length}, improvements: ${improvementsCount}`;
            ctx.clearRect(0, canvas.height - 20, canvas.width, 20);
            const x1_4 = cities[tour[shortestTour.indexOf(tour[0])]].x;
            const y1_4 = cities[tour[shortestTour.indexOf(tour[0])]].y;
            const x2_4 = cities[tour[(shortestTour.indexOf(tour[0]) + 1) % tour.length]].x;
            const y2_4 = cities[tour[(shortestTour.indexOf(tour[0]) + 1) % tour.length]].y;

            ctx.beginPath();
            ctx.moveTo(x1_4, y1_4);
            ctx.lineTo(x2_4, y2_4);
            ctx.stroke();

            ctx.font = '14px Arial';
            ctx.fillStyle = 'black';
            ctx.textAlign = 'left';
            ctx.textBaseline = 'top';
            ctx.fillText(`Tour length: ${tour.length}, improvements: ${improvementsCount}`, 10, canvas.height - 5);
        }
    }

    function animate() {
        requestAnimationFrame(animate);

        for (let i = 0; i < tour.length; i++) {
            const x1 = cities[tour[i]].x;
            const y1 = cities[tour[i]].y;
            const x2 = cities[tour[(i + 1) % tour.length]].x;
            const y2 = cities[tour[(i + 1) % tour.length]].y;

            ctx.beginPath();
            ctx.moveTo(x1, y1);
            ctx.lineTo(x2, y2);
            ctx.stroke();

            ctx.font = '14px Arial';
            ctx.fillStyle = 'black';
            ctx.textAlign = 'center';
            ctx.textBaseline = 'top';
            ctx.fillText(i + 1, (x1 + x2) / 2, (y1 + y2) / 2 - 16);
        }

        ctx.font = '14px Arial';
        ctx.fillStyle = 'black';
        ctx.textAlign = 'left';
        ctx.textBaseline = 'top';
        ctx.fillText(`Tour length: ${tour.length}, improvements: ${improvementsCount}`, 10, canvas.height - 5);

        twoOpt();
    }

    nearestNeighbour();
    animate();
</script>
</body>
</html>
```
MODEL Hgemma4:26bDNF
No usable answer reached the harness (TIMEOUT). Counted as a did-not-finish.
Reveal the models— compare the answers first, then open. Names, blind scores and latencies are hidden until you do.

Who wrote what

Blind labelModelBlind scoreLatencyStatus
MODEL A mistral-small:24b DNF
MODEL B qwen3-coder:30b 40.5 sOK
MODEL C deepseek-r1:14b 36.3 sOK
MODEL D qwen3:8b harness
MODEL E qwen3.5:9b 79.0 sOK
MODEL F qwen3:14b 74.1 sOK
MODEL G llama3.1:8b 148.3 sOK
MODEL H gemma4:26b harness