Nebenläufigkeit und Spickzettel

const std = @import("std");

fn arbeiter(id: usize, ergebnis: *usize) void {
    var summe: usize = 0;
    for (0..1000) |i| summe += i * id;
    ergebnis.* = summe;
}

pub fn main() !void {
    const out = std.io.getStdOut().writer();
    var ergebnisse = [_]usize{0} ** 4;
    var threads: [4]std.Thread = undefined;
    for (&threads, 0..) |*t, i| {
        t.* = try std.Thread.spawn(.{}, arbeiter, .{ i + 1, &ergebnisse[i] });
    }
    for (threads) |t| t.join();
    try out.print("{any}\n", .{ergebnisse});

    var mutex = std.Thread.Mutex{};
    var zaehler: u32 = 0;
    const Helfer = struct {
        fn lauf(m: *std.Thread.Mutex, z: *u32) void {
            for (0..1000) |_| {
                m.lock();
                defer m.unlock();
                z.* += 1;
            }
        }
    };
    var ts: [3]std.Thread = undefined;
    for (&ts) |*t| t.* = try std.Thread.spawn(.{}, Helfer.lauf, .{ &mutex, &zaehler });
    for (ts) |t| t.join();
    try out.print("{d}\n", .{zaehler});
}

{ 499500, 999000, 1498500, 1998000 }
3000