parallel_slice_read.go

package gofu

// IndexBy indexes elements by key concurrently. [ ReadOnly ] [ time: O(n/p); space: O(n)]
//
// Example:
//
//	bigSlice.Parallel(4).IndexBy(func(v int) int { return v % 10 })
func (ps SliceParallel[T]) IndexBy[K comparable](fn func(T) K) Map[K, T] {
	scale := ps.Scale(len(ps.Slice))
	return collectMapResults(ps.MapChunks(scale,
		func(_ int, s Slice[T]) Map[K, T] { return s.IndexBy(fn) },
	))
}

// CountBy counts matching elements concurrently and sums the results. [ ReadOnly ] [ time: O(n/p); space: O(p)]
//
// Example:
//
//	gofu.Slice([]int{1, 2, 3, 4, 5, 6}).Parallel(3).
//	    CountBy(func(v int) bool { return v%2 == 0 }) // 3
func (ps SliceParallel[T]) CountBy(fn func(T) bool) int {
	results := ps.MapChunks(ps.Scale(len(ps.Slice)), func(_ int, chunk Slice[T]) int {
		return chunk.CountBy(fn)
	})
	total := 0
	for _, r := range results {
		total += r
	}
	return total
}