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173 lines
5.3 KiB
V
173 lines
5.3 KiB
V
module pool
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import sync
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import runtime
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[trusted]
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fn C.atomic_fetch_add_u32(voidptr, u32) u32
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pub const (
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no_result = voidptr(0)
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)
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pub struct PoolProcessor {
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thread_cb voidptr
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mut:
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njobs int
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items []voidptr
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results []voidptr
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ntask u32 // reading/writing to this should be atomic
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waitgroup sync.WaitGroup
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shared_context voidptr
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thread_contexts []voidptr
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}
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pub type ThreadCB = fn (p &PoolProcessor, idx int, task_id int) voidptr
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pub struct PoolProcessorConfig {
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maxjobs int
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callback ThreadCB
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}
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// new_pool_processor returns a new PoolProcessor instance.
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// The parameters of new_pool_processor are:
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// context.maxjobs: when 0 (the default), the PoolProcessor will use a
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// number of threads, that is optimal for your system to process your items.
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// context.callback: this should be a callback function, that each worker
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// thread in the pool will run for each item.
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// The callback function will receive as parameters:
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// 1) the PoolProcessor instance, so it can call
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// p.get_item<int>(idx) to get the actual item at index idx
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// 2) idx - the index of the currently processed item
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// 3) task_id - the index of the worker thread in which the callback
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// function is running.
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pub fn new_pool_processor(context PoolProcessorConfig) &PoolProcessor {
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if isnil(context.callback) {
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panic('You need to pass a valid callback to new_pool_processor.')
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}
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mut pool := PoolProcessor{
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items: []
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results: []
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shared_context: voidptr(0)
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thread_contexts: []
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njobs: context.maxjobs
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ntask: 0
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thread_cb: voidptr(context.callback)
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}
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pool.waitgroup.init()
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return &pool
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}
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// set_max_jobs gives you the ability to override the number
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// of jobs *after* the PoolProcessor had been created already.
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pub fn (mut pool PoolProcessor) set_max_jobs(njobs int) {
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pool.njobs = njobs
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}
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// work_on_items receives a list of items of type T,
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// then starts a work pool of pool.njobs threads, each running
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// pool.thread_cb in a loop, until all items in the list,
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// are processed.
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// When pool.njobs is 0, the number of jobs is determined
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// by the number of available cores on the system.
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// work_on_items returns *after* all threads finish.
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// You can optionally call get_results after that.
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pub fn (mut pool PoolProcessor) work_on_items<T>(items []T) {
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pool.work_on_pointers(unsafe { items.pointers() })
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}
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pub fn (mut pool PoolProcessor) work_on_pointers(items []voidptr) {
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mut njobs := runtime.nr_jobs()
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if pool.njobs > 0 {
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njobs = pool.njobs
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}
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pool.thread_contexts = []voidptr{len: items.len}
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pool.results = []voidptr{len: items.len}
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pool.items = []voidptr{cap: items.len}
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pool.items << items
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pool.waitgroup.add(njobs)
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for i := 0; i < njobs; i++ {
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if njobs > 1 {
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go process_in_thread(mut pool, i)
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} else {
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// do not run concurrently, just use the same thread:
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process_in_thread(mut pool, i)
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}
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}
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pool.waitgroup.wait()
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}
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// process_in_thread does the actual work of worker thread.
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// It is a workaround for the current inability to pass a
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// method in a callback.
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fn process_in_thread(mut pool PoolProcessor, task_id int) {
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cb := ThreadCB(pool.thread_cb)
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ilen := pool.items.len
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for {
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idx := int(C.atomic_fetch_add_u32(&pool.ntask, 1))
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if idx >= ilen {
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break
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}
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pool.results[idx] = cb(pool, idx, task_id)
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}
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pool.waitgroup.done()
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}
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// get_item - called by the worker callback.
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// Retrieves a type safe instance of the currently processed item
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pub fn (pool &PoolProcessor) get_item<T>(idx int) T {
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return *(&T(pool.items[idx]))
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}
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// get_result - called by the main thread to get a specific result.
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// Retrieves a type safe instance of the produced result.
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pub fn (pool &PoolProcessor) get_result<T>(idx int) T {
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return *(&T(pool.results[idx]))
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}
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// get_results - get a list of type safe results in the main thread.
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pub fn (pool &PoolProcessor) get_results<T>() []T {
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mut res := []T{cap: pool.results.len}
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for i in 0 .. pool.results.len {
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res << *(&T(pool.results[i]))
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}
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return res
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}
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// get_results_ref - get a list of type safe results in the main thread.
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pub fn (pool &PoolProcessor) get_results_ref<T>() []&T {
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mut res := []&T{cap: pool.results.len}
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for i in 0 .. pool.results.len {
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res << &T(pool.results[i])
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}
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return res
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}
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// set_shared_context - can be called during the setup so that you can
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// provide a context that is shared between all worker threads, like
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// common options/settings.
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pub fn (mut pool PoolProcessor) set_shared_context(context voidptr) {
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pool.shared_context = context
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}
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// get_shared_context - can be called in each worker callback, to get
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// the context set by pool.set_shared_context
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pub fn (pool &PoolProcessor) get_shared_context() voidptr {
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return pool.shared_context
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}
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// set_thread_context - can be called during the setup at the start of
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// each worker callback, so that the worker callback can have some thread
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// local storage area where it can write/read information that is private
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// to the given thread, without worrying that it will get overwritten by
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// another thread
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pub fn (mut pool PoolProcessor) set_thread_context(idx int, context voidptr) {
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pool.thread_contexts[idx] = context
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}
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// get_thread_context - returns a pointer, that was set with
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// pool.set_thread_context . This pointer is private to each thread.
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pub fn (pool &PoolProcessor) get_thread_context(idx int) voidptr {
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return pool.thread_contexts[idx]
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}
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