parallel_slice_loop.go

package gofu

import "sync"

// ForEach calls fn for each element concurrently. [ ReadOnly ] [ time: O(n/p); space: O(1)]
//
// Example:
//
//	bigSlice.Parallel(4).ForEach(func(v int) { fmt.Println(v) })
func (ps SliceParallel[T]) ForEach(fn func(T)) {
	n := ps.Scale(len(ps.Slice))
	ps.ForEachChunk(n, func(_ int, chunk Slice[T]) {
		chunk.ForEach(fn)
	})
}

// ForEachChunk splits the slice into chunks and runs fn on each chunk in a goroutine. [ ReadOnly ] [ time: O(n/p); space: O(1)]
//
// If chunks ≤ 0, the Scale function determines parallelism.
// Runs sequentially when the scale function returns ≤ 1.
//
// Example:
//
//	bigSlice.Parallel(4).ForEachChunk(0, func(i int, chunk gofu.Slice[int]) { ... })
func (ps SliceParallel[T]) ForEachChunk(chunks int, fn func(int, Slice[T])) {
	if chunks <= 0 {
		chunks = ps.Scale(len(ps.Slice))
	}
	if chunks <= 1 || len(ps.Slice) < chunks {
		fn(0, ps.Slice)
		return
	}
	var wg sync.WaitGroup
	ps.Slice.ForEachChunk(chunks, func(i int, chunk Slice[T]) {
		wg.Add(1)
		go func() {
			defer wg.Done()
			fn(i, chunk)
		}()
	})
	wg.Wait()
}

// MapChunks splits the slice into chunks, runs fn on each chunk in a goroutine, and returns results in order. [ Immutable ] [ time: O(n/p); space: O(p)]
//
// If chunks ≤ 0, the Scale function determines parallelism.
// Runs sequentially when the scale function returns ≤ 1. Results are ordered by chunk index.
//
// Example:
//
//	bigSlice.Parallel(3).MapChunks(0, func(i int, chunk gofu.Slice[int]) []int {
//	    return chunk.Filter(func(v int) bool { return v > 0 }).Collect()
//	})
func (ps SliceParallel[T]) MapChunks[R any](chunks int, fn func(int, Slice[T]) R) []R {
	if chunks <= 0 {
		chunks = ps.Scale(len(ps.Slice))
	}
	if chunks <= 1 || len(ps.Slice) < chunks {
		return []R{fn(0, ps.Slice)}
	}
	results := make([]R, chunks)
	var wg sync.WaitGroup
	ps.Slice.ForEachChunk(chunks, func(i int, chunk Slice[T]) {
		wg.Add(1)
		go func() {
			defer wg.Done()
			results[i] = fn(i, chunk)
		}()
	})
	wg.Wait()
	return results
}