PERT Chart Generator: Wait for Both Predecessors

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<body class=""><main><header><div class="eyebrow">Prepared example · source and evidence</div><h1>PERT Chart Generator: Wait for Both Predecessors</h1><p>Rehearsal depends on content and handouts, yet a chart starts it when only handouts are ready. <mark>The merge waits for the later predecessor</mark>; a tidy diagram cannot replace that calculation.</p></header>
<p>Abstract elapsed days. Finish-to-start dependencies; parallel resources assumed unlimited.</p><div id="inputs"></div><nav><button type="button" id="calculate">Calculate network</button><button type="button" id="reset">Reset estimates</button></nav><p id="result" class="result" role="status"></p><div id="ledger" class="ledger"></div><div id="paths" class="paths"></div>
<footer>These elapsed-day estimates exclude staffing and calendar constraints.</footer></main><script>
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(function(){const names=['A','B','C','D','E'],defaults=[[1,2,3],[2,3,4],[1,2,3],[1,1,1],[1,1,1]],deps=['','A','A','B,C','D'];function render(){q('inputs').innerHTML=names.map((id,i)=>`<section><h2>${id} · ${['Outline','Content','Handouts','Rehearsal','Check'][i]}</h2>${['o','m','p'].map((part,j)=>field(id+part,['Optimistic','Most likely','Pessimistic'][j],defaults[i][j])).join('')}${field(id+'deps','Predecessors',deps[i])}</section>`).join('');for(const id of names)for(const part of['o','m','p','deps'])q(id+part).addEventListener('input',()=>{set('result','Network changed; calculate again.');set('ledger','');set('paths','');});set('result','Ready to calculate five activities.');set('ledger','');set('paths','');}on('calculate',()=>{try{const nodes=names.map(id=>{const vals=['o','m','p'].map(part=>{const raw=q(id+part).value.trim();if(!/^\d+(?:\.\d+)?$/.test(raw))throw Error('Use finite nonnegative estimates.');return Number(raw);});if(vals.some(v=>!Number.isFinite(v))||vals[0]>vals[1]||vals[1]>vals[2])throw Error('Require 0 ≤ O ≤ M ≤ P.');const pred=q(id+'deps').value.split(',').map(s=>s.trim()).filter(Boolean);if(pred.some(p=>!names.includes(p))||new Set(pred).size!==pred.length)throw Error('Missing or repeated predecessor ID.');const d=vals[0]+(vals[1]-vals[0])*(2/3)+(vals[2]-vals[0])/6;if(!Number.isFinite(d))throw Error('Derived duration exceeds the supported finite range. Use smaller estimates.');return{id,pred,d};});const ordered=[],remaining=[...nodes];while(remaining.length){const i=remaining.findIndex(n=>n.pred.every(p=>ordered.some(a=>a.id===p)));if(i<0)throw Error('Cycle detected; no valid schedule.');const n=remaining.splice(i,1)[0];n.es=Math.max(0,...n.pred.map(p=>ordered.find(a=>a.id===p).ef));n.ef=n.es+n.d;if(!Number.isFinite(n.es)||!Number.isFinite(n.ef))throw Error('Network exceeds the supported finite range. Use smaller estimates.');ordered.push(n);}const finish=Math.max(...ordered.map(n=>n.ef));for(const n of[...ordered].reverse()){const next=ordered.filter(a=>a.pred.includes(n.id));n.lf=next.length?Math.min(...next.map(a=>a.ls)):finish;n.ls=n.lf-n.d;n.float=n.ls-n.es;if(![n.lf,n.ls,n.float].every(Number.isFinite))throw Error('Network exceeds the supported finite range. Use smaller estimates.');}const critical=[];function walk(n,path){const next=ordered.filter(a=>a.pred.includes(n.id)&&Math.abs(a.float)<1e-9&&Math.abs(a.es-n.ef)<1e-9);if(!next.length&&Math.abs(n.ef-finish)<1e-9)critical.push(path.join('-'));for(const x of next)walk(x,[...path,x.id]);}for(const n of ordered.filter(n=>!n.pred.length&&Math.abs(n.float)<1e-9))walk(n,[n.id]);set('result',`Expected finish ${fmt(finish)} days. Critical paths: ${critical.join('; ')}. Expectations, not promised dates.`);table('ledger',['ID','Duration','ES','EF','LS','LF','Float'],ordered.map(n=>[n.id,...['d','es','ef','ls','lf','float'].map(k=>fmt(n[k]))]));set('paths',ordered.map(n=>n.id+' ← '+(n.pred.join(', ')||'Start')).join(' | '));}catch(error){set('result',error.message);set('ledger','');set('paths','');}});on('reset',render);render();})();})();
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