add nogc tarjan algorithm (#219)

Author: 9il

source/mir/graph/package.d

@@ -17,6 +17,7 @@ import mir.math.common: optmath;
 @optmath:
 
 import mir.series;
+import mir.rc.array;
 import mir.ndslice.iterator: ChopIterator;
 
 ///
@@ -26,6 +27,13 @@ alias Graph(I = uint, J = size_t) = Slice!(GraphIterator!(I, J));
 ///
 alias GraphSeries(T, I = uint, J = size_t) = Series!(T*, GraphIterator!(I, J));
 
+///
+alias RCGraphIterator(I = uint, J = size_t) = ChopIterator!(RCI!size_t, RCI!uint);
+///
+alias RCGraph(I = uint, J = size_t) = Slice!(RCGraphIterator!(I, J));
+///
+alias RCGraphSeries(T, I = uint, J = size_t) = Series!(RCI!T, RCGraphIterator!(I, J));
+
 /++
 Param:
     aaGraph = graph that is represented as associative array

source/mir/graph/tarjan.d

@@ -32,6 +32,7 @@ The implementation is loop based. It does not use recursion and does not have st
 Complexity: worst-case `O(|V| + |E|)`.
 
 Params:
+    RC = nogc mode, refcounted output
     graph = components (ndslice) sorted in the direction of traversal of the graph. Each component is an array of indeces.
 Returns:
     components (ndslice of arrays of indexes)
@@ -44,7 +45,7 @@ See_also:
     $(SUBREF utility, graph)
 +/
 pragma(inline, false)
-auto tarjan(G, I = Unqual!(ForeachType!(ForeachType!G)))(G graph)
+auto tarjan(bool RC = false, G, I = Unqual!(ForeachType!(ForeachType!G)))(G graph)
     if (isUnsigned!I)
 {
     import mir.utility: min;
@@ -87,35 +88,49 @@ auto tarjan(G, I = Unqual!(ForeachType!(ForeachType!G)))(G graph)
         }
     }
 
-    bool[] onStack = new bool[graph.length];
-    I[] stack;
-    IndexNode[] indeces;
-    LoopNode[] loopStack;
-    I index;
+    
     sizediff_t stackIndex;
     sizediff_t backStackIndex = graph.length;
     sizediff_t componentBackStackIndex = graph.length + 1;
 
-    if (__ctfe)
+    static if (RC)
     {
-        stack = new I[graph.length];
-        indeces = new IndexNode[graph.length];
-        loopStack = new LoopNode[componentBackStackIndex];
+        import mir.rc.array;
+        auto onStack = RCArray!bool(graph.length);
+        auto stack = RCArray!I(graph.length, true);
+        auto indeces = RCArray!IndexNode(graph.length, true);
+        auto loopStack = RCArray!LoopNode(componentBackStackIndex, true);
     }
     else
     {
-        () @trusted {
-            import std.array: uninitializedArray;
+        I[] stack;
+        IndexNode[] indeces;
+        LoopNode[] loopStack;
+
+        bool[] onStack = new bool[graph.length];
+        if (__ctfe)
+        {
+
+            stack = new I[graph.length];
+            indeces = new IndexNode[graph.length];
+            loopStack = new LoopNode[componentBackStackIndex];
+        }
+        else
+        {
+            () @trusted {
+                import std.array: uninitializedArray;
 
-            stack = uninitializedArray!(I[])(graph.length);
-            indeces = uninitializedArray!(IndexNode[])(graph.length);
-            loopStack = uninitializedArray!(LoopNode[])(componentBackStackIndex);
-        } ();
+                stack = uninitializedArray!(I[])(graph.length);
+                indeces = uninitializedArray!(IndexNode[])(graph.length);
+                loopStack = uninitializedArray!(LoopNode[])(componentBackStackIndex);
+            } ();
+        }
     }
 
     foreach(ref node; indeces)
         node.index = undefined;
 
+    I index;
     foreach(size_t v; 0u .. graph.length)
     {
         if (indeces[v].isUndefined)
@@ -191,26 +206,42 @@ auto tarjan(G, I = Unqual!(ForeachType!(ForeachType!G)))(G graph)
         }
     }
 
-    S[] pairwiseIndex;
-    if (__ctfe)
+    const indexLength = graph.length + 1 - componentBackStackIndex + 1;
+    static if (RC)
     {
-        pairwiseIndex = new S[graph.length - componentBackStackIndex + 1];
+        auto pairwiseIndex = RCArray!S(indexLength, true);
     }
     else
     {
-        () @trusted {
-            import std.array: uninitializedArray;
-            pairwiseIndex = uninitializedArray!(S[])(graph.length + 1 - componentBackStackIndex + 1);
-        } ();
+        S[] pairwiseIndex;
+        if (__ctfe)
+        {
+            pairwiseIndex = new S[indexLength];
+        }
+        else
+        {
+            () @trusted {
+                import std.array: uninitializedArray;
+                pairwiseIndex = uninitializedArray!(S[])(indexLength);
+            } ();
+        }
     }
-    foreach (i, ref e; loopStack[componentBackStackIndex .. $])
+    foreach (i, ref e; loopStack[][componentBackStackIndex .. $])
     {
         pairwiseIndex[i] = e.index;
     }
     pairwiseIndex[$ - 1] = cast(I) graph.length;
 
     import mir.ndslice.topology: chopped;
-    return (()@trusted {return stack.ptr; }()).chopped(pairwiseIndex);
+    static if (RC)
+    {
+        import core.lifetime: move;
+        return chopped(RCI!I(stack.move), pairwiseIndex.asSlice);
+    }
+    else
+    {
+        return (()@trusted {return stack.ptr; }()).chopped(pairwiseIndex);
+    }
 }
 
 /++
@@ -241,14 +272,21 @@ pure version(mir_test) unittest
         "11": [],
     ].graphSeries;
 
-    auto components = gs.data.tarjan;
 
-    assert(components == [
+    static immutable result = [
         [0],
         [1, 2, 5, 4, 3, 6],
         [10],
         [7, 8, 9],
-        [11]]);
+        [11]];
+
+    // chec GC interface
+    auto components = gs.data.tarjan;
+    assert(components == result);
+    // check @nogc interface
+    // Note: The lambda function is used here to show @nogc mode explicitly.
+    auto rccomponents = (() @nogc => gs.data.tarjan!true )();
+    assert(rccomponents == result);
 }
 
 /++

source/mir/ndslice/topology.d

@@ -3209,7 +3209,7 @@ in
             assert(b);
 }
 do {
-
+    import core.lifetime: move;
     sizediff_t length = bounds._lengths[0] <= 1 ? 0 : bounds._lengths[0] - 1;
     static if (hasLength!Sliceable)
     {
@@ -3222,7 +3222,7 @@ do {
         }
     }
 
-    return typeof(return)([size_t(length)], ChopIterator!(Iterator, Sliceable)(bounds._iterator, sliceable));
+    return typeof(return)([size_t(length)], ChopIterator!(Iterator, Sliceable)(bounds._iterator.move, sliceable.move));
 }
 
 /// ditto

source/mir/rc/array.d

@@ -387,6 +387,9 @@ Thread safe reference counting iterator.
 +/
 struct mir_rci(T)
 {
+    import mir.ndslice.slice: Slice;
+    import mir.ndslice.iterator: IotaIterator;
+
     ///
     T* _iterator;
 
@@ -479,6 +482,36 @@ struct mir_rci(T)
         return _iterator[index];
     }
 
+    /// Returns: slice type of `Slice!(IotaIterator!size_t)`
+    Slice!(IotaIterator!size_t) opSlice(size_t dimension)(size_t i, size_t j) @safe scope const
+        if (dimension == 0)
+    in
+    {
+        assert(i <= j, "RCI!T.opSlice!0: the left opSlice boundary must be less than or equal to the right bound.");
+    }
+    body
+    {
+        return typeof(return)(j - i, typeof(return).Iterator(i));
+    }
+
+    /// Returns: ndslice on top of the refcounted iterator
+    auto opIndex(Slice!(IotaIterator!size_t) slice)
+    {
+        import core.lifetime: move;
+        auto it = this;
+        it += slice._iterator._index;
+        return Slice!(RCI!T)(slice.length, it.move);
+    }
+
+    /// ditto
+    auto opIndex(Slice!(IotaIterator!size_t) slice) const
+    {
+        import core.lifetime: move;
+        auto it = lightConst;
+        it += slice._iterator._index;
+        return Slice!(RCI!(const T))(slice.length,  it.move);
+    }
+
     ///   
     void opUnary(string op)() scope
         if (op == "--" || op == "++")