module sync // * Goal: this file provides a convenient way to run identical tasks over a list // * of items in parallel, without worrying about waitgroups, mutexes and so on. // * // * Usage example: // * pool := sync.new_pool_processor({ callback: worker_cb }) // * //pool.work_on_items(['a','b','c']) // TODO: vfmt and generics // * pool.work_on_pointers(['a','b','c'].pointers()) // * // optionally, you can iterate over the results too: // * for x in pool.get_results() { // * // do stuff with x // * } // * // * See https://github.com/vlang/v/blob/master/vlib/sync/pool_test.v for a // * more detailed usage example. // * // * After all the work is done in parallel by the worker threads in the pool, // * pool.work_on_items will return, and you can then call // * pool.get_results() to retrieve a list of all the results, // * that the worker callbacks returned for each item that you passed. // * The parameters of new_pool_processor are: // * context.maxjobs: when 0 (the default), the PoolProcessor will use an // * optimal for your system number of threads to process your items // * context.callback: this should be a callback function, that each worker // * thread in the pool will run for each item. // * The callback function will receive as parameters: // * 1) the PoolProcessor instance, so it can call // * p.get_item(idx) to get the actual item at index idx // * NB: for now, you are better off calling p.get_string_item(idx) // * or p.get_int_item(idx) ; TODO: vfmt and generics // * 2) idx - the index of the currently processed item // * 3) task_id - the index of the worker thread in which the callback // * function is running. import runtime pub const ( no_result = voidptr(0) ) pub struct PoolProcessor { thread_cb voidptr mut: njobs int items []voidptr results []voidptr ntask int // writing to this should be locked by ntask_mtx. ntask_mtx &sync.Mutex waitgroup &sync.WaitGroup shared_context voidptr thread_contexts []voidptr } pub type ThreadCB fn(p &PoolProcessor, idx int, task_id int)voidptr pub struct PoolProcessorConfig { maxjobs int callback ThreadCB } // new_pool_processor returns a new PoolProcessor instance. pub fn new_pool_processor(context PoolProcessorConfig) &PoolProcessor { if isnil(context.callback) { panic('You need to pass a valid callback to new_pool_processor.') } // TODO: remove this call. // It prevents a V warning about unused module runtime. runtime.nr_jobs() pool := &PoolProcessor { items: [] results: [] shared_context: voidptr(0) thread_contexts: [] njobs: context.maxjobs ntask: 0 ntask_mtx: sync.new_mutex() waitgroup: sync.new_waitgroup() thread_cb: context.callback } return pool } // set_max_jobs gives you the ability to override the number // of jobs *after* the PoolProcessor had been created already. pub fn (pool mut PoolProcessor) set_max_jobs(njobs int) { pool.njobs = njobs } // work_on_items receives a list of items of type T, // then starts a work pool of pool.njobs threads, each running // pool.thread_cb in a loop, untill all items in the list, // are processed. // When pool.njobs is 0, the number of jobs is determined // by the number of available cores on the system. // work_on_items returns *after* all threads finish. // You can optionally call get_results after that. pub fn (pool mut PoolProcessor) work_on_items(items []T) { pool.work_on_pointers( items.pointers() ) } pub fn (pool mut PoolProcessor) work_on_pointers(items []voidptr) { mut njobs := runtime.nr_jobs() if pool.njobs > 0 { njobs = pool.njobs } pool.items = [] pool.results = [] pool.thread_contexts = [] pool.items << items pool.results = [voidptr(0)].repeat(pool.items.len) pool.thread_contexts << [voidptr(0)].repeat(pool.items.len) pool.waitgroup.add(njobs) for i := 0; i < njobs; i++ { go process_in_thread(pool,i) } pool.waitgroup.wait() } // process_in_thread does the actual work of worker thread. // It is a workaround for the current inability to pass a // method in a callback. fn process_in_thread(pool mut PoolProcessor, task_id int) { cb := ThreadCB(pool.thread_cb) mut idx := 0 ilen := pool.items.len for { if pool.ntask >= ilen { break } pool.ntask_mtx.lock() idx = pool.ntask pool.ntask++ pool.ntask_mtx.unlock() pool.results[idx] = cb(pool, idx, task_id) } pool.waitgroup.done() } // get_item - called by the worker callback. // Retrieves a type safe instance of the currently processed item pub fn (pool &PoolProcessor) get_item(idx int) T { return *(&T(pool.items[idx])) } // get_string_item - called by the worker callback. // It does not use generics so it does not mess up vfmt. // TODO: remove the need for this when vfmt becomes smarter. pub fn (pool &PoolProcessor) get_string_item(idx int) string { return *(&string(pool.items[idx])) } // get_int_item - called by the worker callback. // It does not use generics so it does not mess up vfmt. // TODO: remove the need for this when vfmt becomes smarter. pub fn (pool &PoolProcessor) get_int_item(idx int) int { return *(&int(pool.items[idx])) } pub fn (pool &PoolProcessor) get_result(idx int) T { return *(&T(pool.results[idx])) } // get_results - can be called to get a list of type safe results. pub fn (pool &PoolProcessor) get_results() []T { mut res := []T for i in 0 .. pool.results.len { res << *(&T(pool.results[i])) } return res } // set_shared_context - can be called during the setup so that you can // provide a context that is shared between all worker threads, like // common options/settings. pub fn (pool mut PoolProcessor) set_shared_context(context voidptr) { pool.shared_context = context } // get_shared_context - can be called in each worker callback, to get // the context set by pool.set_shared_context pub fn (pool &PoolProcessor) get_shared_context() voidptr { return pool.shared_context } // set_thread_context - can be called during the setup at the start of // each worker callback, so that the worker callback can have some thread // local storage area where it can write/read information that is private // to the given thread, without worrying that it will get overwritten by // another thread pub fn (pool mut PoolProcessor) set_thread_context(idx int, context voidptr) { pool.thread_contexts[idx] = context } // get_thread_context - returns a pointer, that was set with // pool.set_thread_context . This pointer is private to each thread. pub fn (pool &PoolProcessor) get_thread_context(idx int) voidptr { return pool.thread_contexts[idx] }