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  1. PO
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    <p>I would rather do it in a single loop. My produces a different result from yours. Yours scheduled 2/3 of all the jobs. Mine scheduled all. I will add explanations later. Going off for an appointment now.</p> <pre><code>public class Job { public static long Iterations; public int Id; public int Priority; public DateTime Begin; public DateTime End; public bool Overlaps(Job other) { Iterations++; return this.End &gt; other.Begin &amp;&amp; this.Begin &lt; other.End; } } public class Assignment : IComparable&lt;Assignment&gt; { public Job Job; public int Core; #region IComparable&lt;Assignment&gt; Members public int CompareTo(Assignment other) { return Job.Begin.CompareTo(other.Job.Begin); } #endregion } class Program { static void Main(string[] args) { const int Jobs = 1000; const int Cores = 2; const int ConcurrentJobs = Cores + 1; const int Priorities = Cores + 3; DateTime startTime = new DateTime(2011, 3, 1, 0, 0, 0, 0); Console.WriteLine(string.Format("{0} Jobs x {1} Cores", Jobs, Cores)); var timer = Stopwatch.StartNew(); Console.WriteLine("Populating data"); var jobs = new List&lt;Job&gt;(); for (int jobId = 0; jobId &lt; Jobs; jobId++) { var jobStart = startTime.AddHours(jobId / ConcurrentJobs).AddMinutes(jobId % ConcurrentJobs); jobs.Add(new Job() { Id = jobId, Priority = jobId % Priorities, Begin = jobStart, End = jobStart.AddHours(0.5) }); } Console.WriteLine(string.Format("Completed in {0:n}ms", timer.ElapsedMilliseconds)); timer.Reset(); Console.WriteLine("Assigning Jobs to Cores"); List&lt;Assignment&gt;[] assignments = new List&lt;Assignment&gt;[Cores]; for (int core = 0; core &lt; Cores; core++) assignments[core] = new List&lt;Assignment&gt;(); Job[] lastJobs = new Job[Cores]; foreach (Job j in jobs) { Job job = j; bool assigned = false; for (int core = 0; core &lt; Cores; core++) { if (lastJobs[core] == null || !lastJobs[core].Overlaps(job)) { // Assign directly if no last job or no overlap with last job lastJobs[core] = job; assignments[core].Add(new Assignment { Job = job, Core = core }); assigned = true; break; } else if (job.Priority &gt; lastJobs[core].Priority) { // Overlap and higher priority, so we replace Job temp = lastJobs[core]; lastJobs[core] = job; job = temp; // Will try to later assign to other core assignments[core].Add(new Assignment { Job = job, Core = core }); assigned = true; break; } } if (!assigned) { // TODO: What to do if not assigned? Your code seems to just ignore them } } List&lt;Assignment&gt; merged = new List&lt;Assignment&gt;(); for (int core = 0; core &lt; Cores; core++) merged.AddRange(assignments[core]); merged.Sort(); Console.WriteLine(string.Format("Completed in {0:n}ms", timer.ElapsedMilliseconds)); timer.Reset(); Console.WriteLine(string.Format("\nTotal Comparisons: {0:n}", Job.Iterations)); Job.Iterations = 0; // Reset to count again { IEnumerable&lt;Assignment&gt; assignments2 = null; for (int core = 0; core &lt; Cores; core++) { // avoid modified closures by creating local variables int localCore = core; var localAssignments = assignments2; // Step 1: Determine the remaining jobs var remainingJobs = localAssignments == null ? jobs : from j in jobs where !(from a in localAssignments select a.Job).Contains(j) select j; // Step 2: Assign the top priority job in any time-slot to the core var assignmentsForCore = from s1 in remainingJobs where (from s2 in remainingJobs where s1.Overlaps(s2) orderby s2.Priority select s2).First().Equals(s1) select new Assignment { Job = s1, Core = localCore }; // Step 3: Accumulate the results (unfortunately requires a .ToList() to avoid massive over-joins) assignments2 = assignments2 == null ? assignmentsForCore.ToList() : assignments2.Concat(assignmentsForCore.ToList()); } // This is where I'd like to Execute the query one single time across all cores, but have to do intermediate steps to avoid massive-over-joins assignments2 = assignments2.ToList(); Console.WriteLine(string.Format("Completed in {0:n}ms", timer.ElapsedMilliseconds)); Console.WriteLine("\nJobs:"); foreach (var job in jobs.Take(20)) { Console.WriteLine(string.Format("{0}-{1} Id {2} P{3}", job.Begin, job.End, job.Id, job.Priority)); } Console.WriteLine("\nAssignments:"); foreach (var assignment in assignments2.OrderBy(a =&gt; a.Job.Begin).Take(10)) { Console.WriteLine(string.Format("{0}-{1} Id {2} P{3} C{4}", assignment.Job.Begin, assignment.Job.End, assignment.Job.Id, assignment.Job.Priority, assignment.Core)); } if (merged.Count != assignments2.Count()) System.Console.WriteLine("Difference count {0}, {1}", merged.Count, assignments2.Count()); for (int i = 0; i &lt; merged.Count() &amp;&amp; i &lt; assignments2.Count(); i++) { var a2 = assignments2.ElementAt(i); var a = merged[i]; if (a.Job.Id != a2.Job.Id) System.Console.WriteLine("Difference at {0} {1} {2}", i, a.Job.Begin, a2.Job.Begin); if (i % 100 == 0) Console.ReadKey(); } } Console.WriteLine(string.Format("\nTotal Comparisons: {0:n}", Job.Iterations)); Console.WriteLine("Any key to continue"); Console.ReadKey(); } } </code></pre> <hr> <p>Removed due to major bug. Reworking on it.. :P</p>
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    1. POHow to schedule jobs without overlap using LINQ to Objects?
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    1. USFun Mun Pieng
    1. USFun Mun Pieng
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    1. COThanks for the suggestion. Unfortunately this doesn't use LINQ, which is one of the requirements.
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    2. CO@timherby, I did some transformation magic. Refer to the edited answer for the LINQ version.
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    3. CObut wait, there's a bug... correcting now
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