D語言的並行迭代器

Question

我正在嘗試以D語言實現一種圖形數據結構，該結構支持對節點和邊集進行並行迭代。

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);
    }

這是一個順序節點迭代器方法：

/**
 * 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);
    }
}

像這樣工作，並且似乎工作正常：

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

現在，我嘗試使用'std.parallelism'模塊的並行版本：

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

但這給了我一個編譯器錯誤。 我在這里做錯了什么？

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需要一個范圍。 使用std.range.iota獲得等於0 .. z的范圍std.range.iota ： foreach (v; parallel(iota(z))) {...}