D語言中的並行迭代器

Question

我試圖在D語言中實現一個支持並行迭代遍歷節點和邊集的圖數據結構。

alias ulong index; 
alias index node; 
alias ulong count; 

class Graph { 
    index z; // max node index 
    count n; // number of nodes 
    count m; // number of edges 
    node[][] adja; // adjacency list 
    count[] deg; // node degree 

    this(count n = 0) { 
     this.z = n; 
     this.n = n; 
     this.m = 0; 
     this.adja = new node[][](this.z, 0); 
     this.deg = new count[](this.z); 
    } 

這裏有一個連續的節點迭代方法：

/** 
* Iterate over all nodes of the graph and call handler (lambda closure). 
*/ 
void forNodes(F)(F handle) { 
    foreach (node v; 0 .. z) { 
     // call here 
     handle(v); 
    } 
} 

工作原理是這樣的，似乎很好地工作：

ulong sum1 = 0; 
G.forNodes((node v) { 
    sum1 += v; 
}); 

現在，我嘗試使用「std.parallelism並行版本'模塊：

void parallelForNodes(F)(F handle) { 
    foreach (node v; taskPool.parallel(z)) { 
     // call here 
     handle(v); 
    } 
} 

但是這給了我一個編譯器錯誤。我在這裏做錯了什麼？

cls ~/workspace/Prototypes/PLPd $ ./main.d 
/usr/local/Cellar/dmd/2.063/src/phobos/std/parallelism.d(3795): Error: cannot have parameter of type void 
/usr/local/Cellar/dmd/2.063/src/phobos/std/parallelism.d(3796): Error: cannot have parameter of type void 
/usr/local/Cellar/dmd/2.063/src/phobos/std/parallelism.d(1539): Error: template instance std.parallelism.ParallelForeach!(ulong) error instantiating 
Graph.d(90):  instantiated from here: parallel!(ulong) 
./main.d(100):  instantiated from here: parallelForNodes!(void delegate(ulong v) nothrow @safe) 
Graph.d(90): Error: template instance std.parallelism.TaskPool.parallel!(ulong) error instantiating 
./main.d(100):  instantiated from here: parallelForNodes!(void delegate(ulong v) nothrow @safe) 
./main.d(100): Error: template instance Graph.Graph.parallelForNodes!(void delegate(ulong v) nothrow @safe) error instantiating 
Failed: 'dmd' '-v' '-o-' './main.d' '-I.' 

Answer 1

parallel取一個範圍。使用std.range.iota可獲得相當於0 .. z的範圍：foreach (v; parallel(iota(z))) {...}