public override GroupByResults Group(ITableResults resTable)
{
// Create hashers and equality comparers.
// The hashers receive also the equality comparer as cache.
CreateHashersAndComparers(out ExpressionComparer[] comparers, out ExpressionHasher[] hashers);
return(this.ParallelGroupBy(RowEqualityComparerInt.Factory(resTable, comparers, new RowHasher(hashers), false), resTable));
}
protected override GroupByJob[] CreateSpecJobs(GroupByJob[] jobs, RowEqualityComparerInt equalityComparer, ITableResults resTable, int current, int addition)
{
var concurrentDictBuckets = new ConcurrentDictionary <int, AggregateBucketResult[]>(equalityComparer);
for (int i = 0; i < jobs.Length - 1; i++)
{
jobs[i] = new GroupByJobBuckets(concurrentDictBuckets, this.aggregates, resTable, current, current + addition);
current += addition;
}
jobs[jobs.Length - 1] = new GroupByJobBuckets(concurrentDictBuckets, this.aggregates, resTable, current, resTable.NumberOfMatchedElements);
return(jobs);
}
/// <summary>
/// Creates jobs for the parallel group by.
/// Note that the last job in the array has the end set to the end of the result table.
/// Each job will receive a range from result table, aggregates and a global place to store groups and the aggregated values.
/// Note that there is a single comparer for the ConcurrentDictionary, thus no caching of the expression is done.
/// </summary>
private GroupByJob[] CreateJobs(RowEqualityComparerInt equalityComparer, ITableResults resTable)
{
GroupByJob[] jobs = new GroupByJob[this.ThreadCount];
int current = 0;
int addition = resTable.NumberOfMatchedElements / this.ThreadCount;
if (addition == 0)
{
throw new ArgumentException($"{this.GetType()}, a range for a thread cannot be 0.");
}
return(CreateSpecJobs(jobs, equalityComparer, resTable, current, addition));
}
protected override GroupByJob[] CreateSpecJobs(GroupByJob[] jobs, RowEqualityComparerInt equalityComparer, ITableResults resTable, int current, int addition)
{
var aggResults = AggregateArrayResults.CreateArrayResults(this.aggregates);
var concurrentDictArrays = new ConcurrentDictionary <int, int>(equalityComparer);
int capture = 0;
Func <int, int> positionFactory = (int x) => { return(Interlocked.Increment(ref capture)); };
Semaphore semaphore = new Semaphore(this.ThreadCount, this.ThreadCount);
for (int i = 0; i < jobs.Length - 1; i++)
{
jobs[i] = new GroupByJobArrays(concurrentDictArrays, this.aggregates, resTable, current, current + addition, aggResults, positionFactory, semaphore, jobs.Length);
current += addition;
}
jobs[jobs.Length - 1] = new GroupByJobArrays(concurrentDictArrays, this.aggregates, resTable, current, resTable.NumberOfMatchedElements, aggResults, positionFactory, semaphore, jobs.Length);
return(jobs);
}
private GroupByResults ParallelGroupBy(RowEqualityComparerInt equalityComparer, ITableResults resTable)
{
var jobs = CreateJobs(equalityComparer, resTable);
var tasks = new Task[this.ThreadCount - 1];
for (int i = 0; i < tasks.Length; i++)
{
var tmp = jobs[i];
tasks[i] = Task.Factory.StartNew(() => SingleThreadGroupByWork(tmp));
}
// The main thread works with the last job in the array.
SingleThreadGroupByWork(jobs[jobs.Length - 1]);
Task.WaitAll(tasks);
// No merge needed.
return(CreateGroupByResults(jobs[0]));
}
protected abstract GroupByJob[] CreateSpecJobs(GroupByJob[] jobs, RowEqualityComparerInt equalityComparer, ITableResults resTable, int current, int addition);