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package sync
// A barrier enabling multiple threads to synchronize the beginning of some computation
/*
* Example:
*
* package example
*
* import "core:fmt"
* import "core:sync"
* import "core:thread"
*
* barrier := &sync.Barrier{};
*
* main :: proc() {
* fmt.println("Start");
*
* THREAD_COUNT :: 4;
* threads: [THREAD_COUNT]^thread.Thread;
*
* sync.barrier_init(barrier, THREAD_COUNT);
* defer sync.barrier_destroy(barrier);
*
*
* for _, i in threads {
* threads[i] = thread.create_and_start(proc(t: ^thread.Thread) {
* // Same messages will be printed together but without any interleaving
* fmt.println("Getting ready!");
* sync.barrier_wait(barrier);
* fmt.println("Off their marks they go!");
* });
* }
*
* for t in threads {
* thread.destroy(t); // join and free thread
* }
* fmt.println("Finished");
* }
*
*/
Barrier :: struct {
mutex: Blocking_Mutex,
cond: Condition,
index: int,
generation_id: int,
thread_count: int,
}
barrier_init :: proc(b: ^Barrier, thread_count: int) {
blocking_mutex_init(&b.mutex);
condition_init(&b.cond, &b.mutex);
b.index = 0;
b.generation_id = 0;
b.thread_count = thread_count;
}
barrier_destroy :: proc(b: ^Barrier) {
blocking_mutex_destroy(&b.mutex);
condition_destroy(&b.cond);
}
// Block the current thread until all threads have rendezvoused
// Barrier can be reused after all threads rendezvoused once, and can be used continuously
barrier_wait :: proc(b: ^Barrier) -> (is_leader: bool) {
blocking_mutex_lock(&b.mutex);
defer blocking_mutex_unlock(&b.mutex);
local_gen := b.generation_id;
b.index += 1;
if b.index < b.thread_count {
for local_gen == b.generation_id && b.index < b.thread_count {
condition_wait_for(&b.cond);
}
return false;
}
b.index = 0;
b.generation_id += 1;
condition_broadcast(&b.cond);
return true;
}
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