private static IEnumerable <IFusionOperator> Optimize(IFusionOperator[] chain)
{
// TODO: these optimizations can be moved to the expression space above the plan
var cur = default(IFusionOperator);
foreach (var op in chain)
{
if (cur != null)
{
if (cur is WhereFactory where1 && op is WhereFactory where2)
{
var p1 = where1.Predicate;
var p2 = where2.Predicate;
var x = Expression.Parameter(cur.OutputType);
var p = Expression.Lambda(Expression.AndAlso(Expression.Invoke(p1, x), Expression.Invoke(p2, x)), x);
cur = new WhereFactory {
Predicate = p
};
}
else if (cur is TakeFactory take1 && op is TakeFactory take2)
{
// TODO: Count should be an expression (which could be constant, allowing for this optimization)
var n1 = take1.Count;
var n2 = take2.Count;
var n = Math.Min(n1, n2);
cur = new TakeFactory {
Count = n
};
}
private static void Take()
{
var tf = new TakeFactory
{
Count = 3,
OutputType = typeof(int)
};
var ff = new SinkFactory
{
OutputType = typeof(int)
};
var chain = new IFusionOperator[]
{
tf, // .Take(3)
ff
};
var ivt = Compile(typeof(int), chain);
var res = new List <int>();
var err = default(Exception);
var fin = false;
var otp = Observer.Create <int>(res.Add, ex => err = ex, () => fin = true);
var dsp = System.Reactive.Disposables.Disposable.Empty;
var iv = (IObserver <int>)Activator.CreateInstance(ivt, new object[] { otp, dsp });
iv.OnNext(0);
iv.OnNext(1);
iv.OnNext(2);
iv.OnNext(3);
iv.OnNext(4);
iv.OnCompleted();
Assert(res.SequenceEqual(new[] { 0, 1, 2 }));
Assert(err == null);
Assert(fin);
}
private static void Old()
{
// TODO: implement a few operators in terms of others and see fusion emit the same code
// e.g. xs.Last() == xs.Aggreggate((a, x) => x)
//
// Aggregate
// - Count/LongCount
// Average/Sum/Min/Max
// Any/All/IsEmpty
// - First
// - Last
// Single
// Contains
// ElementAt
// - IgnoreElements
// Scan
// Sample
// - Take
// Skip
// TakeWhile/SkipWhile
// Finally
//
// CombineLatest
// SequenceEqual
// TakeUntil
//
// SkipUntil
// StartWith
//
// Merge
// SelectMany
// Switch
//
var wf1 = new WhereFactory
{
Predicate = (Expression <Func <int, bool> >)(x => x > 0)
};
var wf2 = new WhereIndexedFactory
{
Predicate = (Expression <Func <int, int, bool> >)((x, i) => x != 0 && i < int.MaxValue)
};
var df = new DistinctUntilChangedFactory
{
OutputType = typeof(int)
};
var sf1 = new SelectFactory
{
Selector = (Expression <Func <int, int> >)(x => x * 2)
};
var sf2 = new SelectIndexedFactory
{
Selector = (Expression <Func <int, int, int> >)((x, i) => x * 3 + i)
};
var tf1 = new TakeFactory
{
OutputType = typeof(int),
Count = 1000
};
var tf2 = new TakeFactory
{
OutputType = typeof(int),
Count = 2000
};
var af = new SumFactory(typeof(int));
var ff = new SinkFactory
{
OutputType = typeof(int)
};
var chain = new IFusionOperator[]
{
wf1, // .Where(x => x > 0)
wf2, // .Where((x, i) => x != 0 && i < int.MaxValue)
df, // .DistinctUntilChanged()
sf1, // .Select(x => x * 2)
sf2, // .Select((x, i) => x * 3 + i)
tf1, // .Take(1000)
tf2, // .Take(2000)
af, // .Sum()
ff
};
var ivt = Compile(typeof(int), chain);
Test(ivt);
}