127 lines
4.1 KiB
Zig
127 lines
4.1 KiB
Zig
const builtin = @import("builtin");
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const AtomicOrder = builtin.AtomicOrder;
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/// Many reader, many writer, non-allocating, thread-safe, lock-free
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pub fn Stack(comptime T: type) type {
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return struct {
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root: ?&Node,
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pub const Self = this;
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pub const Node = struct {
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next: ?&Node,
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data: T,
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};
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pub fn init() Self {
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return Self {
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.root = null,
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};
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}
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/// push operation, but only if you are the first item in the stack. if you did not succeed in
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/// being the first item in the stack, returns the other item that was there.
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pub fn pushFirst(self: &Self, node: &Node) ?&Node {
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node.next = null;
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return @cmpxchgStrong(?&Node, &self.root, null, node, AtomicOrder.SeqCst, AtomicOrder.SeqCst);
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}
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pub fn push(self: &Self, node: &Node) void {
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var root = @atomicLoad(?&Node, &self.root, AtomicOrder.SeqCst);
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while (true) {
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node.next = root;
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root = @cmpxchgWeak(?&Node, &self.root, root, node, AtomicOrder.SeqCst, AtomicOrder.SeqCst) ?? break;
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}
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}
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pub fn pop(self: &Self) ?&Node {
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var root = @atomicLoad(?&Node, &self.root, AtomicOrder.Acquire);
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while (true) {
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root = @cmpxchgWeak(?&Node, &self.root, root, (root ?? return null).next, AtomicOrder.SeqCst, AtomicOrder.SeqCst) ?? return root;
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}
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}
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pub fn isEmpty(self: &Self) bool {
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return @atomicLoad(?&Node, &self.root, AtomicOrder.SeqCst) == null;
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}
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};
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}
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const std = @import("std");
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const Context = struct {
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allocator: &std.mem.Allocator,
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stack: &Stack(i32),
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put_sum: isize,
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get_sum: isize,
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get_count: usize,
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puts_done: u8, // TODO make this a bool
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};
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const puts_per_thread = 1000;
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const put_thread_count = 3;
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test "std.atomic.stack" {
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var direct_allocator = std.heap.DirectAllocator.init();
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defer direct_allocator.deinit();
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var plenty_of_memory = try direct_allocator.allocator.alloc(u8, 64 * 1024 * 1024);
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defer direct_allocator.allocator.free(plenty_of_memory);
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var fixed_buffer_allocator = std.heap.ThreadSafeFixedBufferAllocator.init(plenty_of_memory);
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var a = &fixed_buffer_allocator.allocator;
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var stack = Stack(i32).init();
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var context = Context {
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.allocator = a,
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.stack = &stack,
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.put_sum = 0,
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.get_sum = 0,
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.puts_done = 0,
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.get_count = 0,
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};
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var putters: [put_thread_count]&std.os.Thread = undefined;
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for (putters) |*t| {
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*t = try std.os.spawnThread(&context, startPuts);
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}
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var getters: [put_thread_count]&std.os.Thread = undefined;
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for (getters) |*t| {
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*t = try std.os.spawnThread(&context, startGets);
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}
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for (putters) |t| t.wait();
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_ = @atomicRmw(u8, &context.puts_done, builtin.AtomicRmwOp.Xchg, 1, AtomicOrder.SeqCst);
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for (getters) |t| t.wait();
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std.debug.assert(context.put_sum == context.get_sum);
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std.debug.assert(context.get_count == puts_per_thread * put_thread_count);
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}
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fn startPuts(ctx: &Context) u8 {
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var put_count: usize = puts_per_thread;
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var r = std.rand.DefaultPrng.init(0xdeadbeef);
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while (put_count != 0) : (put_count -= 1) {
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std.os.time.sleep(0, 1); // let the os scheduler be our fuzz
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const x = @bitCast(i32, r.random.scalar(u32));
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const node = ctx.allocator.create(Stack(i32).Node) catch unreachable;
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node.data = x;
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ctx.stack.push(node);
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_ = @atomicRmw(isize, &ctx.put_sum, builtin.AtomicRmwOp.Add, x, AtomicOrder.SeqCst);
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}
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return 0;
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}
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fn startGets(ctx: &Context) u8 {
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while (true) {
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while (ctx.stack.pop()) |node| {
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std.os.time.sleep(0, 1); // let the os scheduler be our fuzz
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_ = @atomicRmw(isize, &ctx.get_sum, builtin.AtomicRmwOp.Add, node.data, builtin.AtomicOrder.SeqCst);
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_ = @atomicRmw(usize, &ctx.get_count, builtin.AtomicRmwOp.Add, 1, builtin.AtomicOrder.SeqCst);
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}
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if (@atomicLoad(u8, &ctx.puts_done, builtin.AtomicOrder.SeqCst) == 1) {
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break;
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}
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}
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return 0;
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}
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