var jobStrings = []; // now using preflight based on CPU speed var workerScript; var workerPool = []; var jobStringIndex = 0; var outOfWork=false; var pfChecks = 0; var pfStartLen = 9; var pfStartTime, pfEndTime; var pfWorker; var pfDone = false; var pfThreadTime = 0; function preflight(){ /* average time ratio for threads adding 1 letter on * PC: 1.99x previous letter * mobile: 1.93x previous letter * Therefore, 2x the time each +1 letter seems like a reasonable target */ // start strlen 10 and iterate serially until cumulative time hits 600ms. Array max will be +5 characters across a total span of 16 threads. var blob = new Blob([workerScript], {type: 'text/javascript'}); var blobUrl = URL.createObjectURL(blob); pfWorker = new Worker(blobUrl); pfWorker.onmessage = function() { switch (event.data.msg) { case "GiveMeSomethingToDo": if(pfDone===true){ pfWorker.postMessage({"cmd":"NoMoreWork"}); setTimeout(go, 20); } else { pfChecks += 1; var displayNum = pfChecks + 5; document.getElementById("preflights").innerHTML = "" + displayNum + ": A" + "C".repeat(displayNum); pfWorker.postMessage({ "cmd":"DoThis", "jobID":pfChecks, "stringToScan":"A" + "C".repeat(pfStartLen+pfChecks) }); } break; case "IDidIt": pfThreadTime += parseInt(event.data.duration); // ms if(pfThreadTime >= 600) { pfDone = true; var highestJobLen = parseInt(event.data.jobIFinished) + pfStartLen + 4; // load multithreaded jobs based on preflight up to 1/3s for(var i=0; i<16; i++) { jobStrings.push("A" + "C".repeat(highestJobLen - i)); } } break; default: break; } }; pfWorker.postMessage({ "cmd":"initialize", "worker":0 }); pfWorker.postMessage({ "cmd":"DoThis", "jobID":pfChecks, "stringToScan":"A" + "C".repeat(pfChecks+pfStartLen) }); } var preamble = "Regular expressions suffer from a 'runaway' problem known as catastrophic backtracking. Here, adding just 1 letter affects regex performance in an undesirable way.
Thoughts: Check your inputs. Use background threads for risky calculations. Simultaneous execution really matters.

Background threads (string len: seconds)"; function getNextJob(){ if(jobStringIndex == jobStrings.length) { outOfWork = true; return false; } return jobStringIndex++; } function fillDocumentWithSlots() { var el; el = document.createElement("div"); el.innerHTML = preamble; document.body.appendChild(el); for(var jobNumber = 0; jobNumber < jobStrings.length; jobNumber++) { el = document.createElement("div"); el.id = "job" + jobNumber; el.innerHTML = jobStrings[jobNumber].length + ": pending"; el.style['float']="left"; el.style['width']="25%"; document.body.appendChild(el); } el = document.createElement("hr"); document.body.appendChild(el); var splitEl = document.createElement("div"); splitEl.innerHTML = "

Foreground CSS animation (independent of jobs)

"; el = document.createElement('div'); el.id = 'yy'; el.style.float="left"; splitEl.appendChild(el); el = document.createElement('div'); el.id = "WallTime"; el.style.float="left"; el.innerHTML = "Statistics: (waiting for jobs to finish)"; splitEl.appendChild(el); document.body.appendChild(splitEl); // foreground animation var elStyle = document.createElement('style'); elStyle.type = 'text/css'; if (elStyle.styleSheet) elStyle.styleSheet.cssText = yinyangScript; else elStyle.appendChild(document.createTextNode(yinyangScript)); document.getElementsByTagName("head")[0].appendChild(elStyle); } function showWhatsGoingOut(jobTaken, whoTookIt) { var id = "job"+jobTaken; document.getElementById(id).innerHTML = "" + jobStrings[jobTaken].length + ": wkr [" + whoTookIt +"]"; } function showWallTime(duration) { document.getElementById("WallTime").innerHTML = "Wall time: " + duration/1000 + " seconds
Thread time: " + threadTime/1000 + " seconds
Time saved by threading:
" + (threadTime-duration)/1000 + " seconds"; } function showWhatFinished(jobTaken, howLongItTook){ var id = "job" + jobTaken; document.getElementById(id).innerHTML = "" + jobStrings[jobTaken].length + ": " + howLongItTook/1000 + ""; } // These are messages FROM the worker function workerListener(){ var workerTalking = workerPool[event.data.worker]; switch (event.data.msg) { case "GiveMeSomethingToDo": var jobID = getNextJob(); if(outOfWork){ workerTalking.postMessage({ "cmd":"NoMoreWork" }); } else { showWhatsGoingOut(jobID, event.data.worker); workerTalking.postMessage({ "cmd":"DoThis", "jobID":jobID, "stringToScan":jobStrings[jobID] }); } break; case "IDidIt": threadTime += parseInt(event.data.duration); // ms jobsFinished += 1; if(jobsFinished == jobStrings.length) showWallTime(Date.now() - startTime); showWhatFinished(event.data.jobIFinished, event.data.duration); break; default: break; } } function fillWorkerPool(howMany){ for(var index=0; index

Runaway regex: catastrophic backtracking (safe threads) [refactor]