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improvements for async-io

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Chris Boesch
2026-04-06 19:30:56 +02:00
parent aeeb18931d
commit 09bae6a70e
3 changed files with 37 additions and 25 deletions
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6
build.zig
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@@ -1180,9 +1180,9 @@ const exercises = [_]Exercise{
.{ .{
.main_file = "093_async9.zig", .main_file = "093_async9.zig",
.output = .output =
\\Main thread continues... \\Computing concurrently!
\\Computing on a separate thread! \\Main continues...
\\Main thread done waiting. \\Main done waiting.
\\Result: 123 \\Result: 123
, // pay attention to the comma , // pay attention to the comma
}, },

42
exercises/093_async9.zig
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@@ -5,22 +5,29 @@
// The difference: // The difference:
// //
// io.async(): // io.async():
// * The function MAY run on another thread, or it may run // * The function MAY run on a separate unit of concurrency,
// immediately on the current thread (synchronously). // or it may run immediately on the caller (synchronously).
// * Never fails — if no thread is available, it just runs // * Never fails — if no concurrency is available, it just
// the function right away. // runs the function right away.
// * More portable, works with all Io backends. // * More portable, works with all Io backends.
// //
// io.concurrent(): // io.concurrent():
// * GUARANTEES a separate unit of concurrency (a real thread // * GUARANTEES a separate unit of concurrency.
// in the Threaded backend).
// * Can fail with error.ConcurrencyUnavailable if resources // * Can fail with error.ConcurrencyUnavailable if resources
// are exhausted or the backend doesn't support it. // are exhausted or the backend doesn't support it.
// * Use when you NEED true parallelism. // * Use when you NEED the task to run independently of the
// caller.
//
// What is a "unit of concurrency"? That depends on the backend!
// The Threaded backend uses OS threads. But the Evented backends
// (Uring, Kqueue, Dispatch) use M:N green threads / fibers,
// which can provide concurrency even on a SINGLE OS thread.
// Your code doesn't need to know the difference.
// //
// Because concurrent() can fail, you must handle the error: // Because concurrent() can fail, you must handle the error:
// //
// var future = try io.concurrent(myFn, .{args}); // var future = try io.concurrent(myFn, .{args});
// defer _ = future.cancel(io);
// const result = future.await(io); // const result = future.await(io);
// //
// Notice the 'try' — that's the key difference in usage! // Notice the 'try' — that's the key difference in usage!
@@ -33,25 +40,30 @@ const print = std.debug.print;
pub fn main(init: std.process.Init) !void { pub fn main(init: std.process.Init) !void {
const io = init.io; const io = init.io;
// Launch with a guaranteed separate thread. // Launch with a guaranteed separate unit of concurrency.
// Which Io method guarantees true concurrency? // Which Io method guarantees this?
// (Hint: unlike io.async, this one can fail!) // (Hint: unlike io.async, this one can fail!)
var future = try io.???(compute, .{io}); var future = try io.???(compute, .{io});
defer _ = future.cancel(io);
print("Main thread continues...\n", .{}); // Note: All breaks in this excercise (using sleep)
// are only necessary for a deterministic result.
// Wait 100 millisecond so the output order is deterministic.
io.sleep(std.Io.Duration.fromMilliseconds(100), .awake) catch {}; io.sleep(std.Io.Duration.fromMilliseconds(100), .awake) catch {};
print("Main thread done waiting.\n", .{}); print("Main continues...\n", .{});
// Wait 1 second for the output order.
io.sleep(std.Io.Duration.fromMilliseconds(200), .awake) catch {};
print("Main done waiting.\n", .{});
const result = future.await(io); const result = future.await(io);
print("Result: {}\n", .{result}); print("Result: {}\n", .{result});
} }
fn compute(io: std.Io) u32 { fn compute(io: std.Io) u32 {
print("Computing on a separate thread!\n", .{}); print("Computing concurrently!\n", .{});
// Simulate some work. // Simulate some work.
io.sleep(std.Io.Duration.fromMilliseconds(200), .awake) catch return 0; io.sleep(std.Io.Duration.fromMilliseconds(400), .awake) catch return 0;
return 123; return 123;
} }

14
patches/patches/093_async9.patch
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@@ -1,11 +1,11 @@
--- exercises/093_async9.zig 2026-04-03 13:44:50.526780809 +0200 --- exercises/093_async9.zig 2026-04-06 19:26:11.388025362 +0200
+++ answers/093_async9.zig 2026-04-03 13:44:54.957870294 +0200 +++ answers/093_async9.zig 2026-04-06 19:18:36.242931688 +0200
@@ -36,7 +36,7 @@ @@ -43,7 +43,7 @@
// Launch with a guaranteed separate thread. // Launch with a guaranteed separate unit of concurrency.
// Which Io method guarantees true concurrency? // Which Io method guarantees this?
// (Hint: unlike io.async, this one can fail!) // (Hint: unlike io.async, this one can fail!)
- var future = try io.???(compute, .{io}); - var future = try io.???(compute, .{io});
+ var future = try io.concurrent(compute, .{io}); + var future = try io.concurrent(compute, .{io});
defer _ = future.cancel(io);
print("Main thread continues...\n", .{}); // Note: All breaks in this excercise (using sleep)