Use a lock and channel free parallelization for subseq scoring

tools/tui/subseq/score.go

@@ -8,7 +8,6 @@ import (
 	"strings"
 
 	"github.com/kovidgoyal/kitty/tools/utils"
-	"github.com/kovidgoyal/kitty/tools/utils/images"
 )
 
 var _ = fmt.Print
@@ -202,10 +201,7 @@ func score_item(item string, idx int, needle []rune, opts *resolved_options_type
 }
 
 func ScoreItems(query string, items []string, opts Options) []*Match {
-	ctx := images.Context{}
-	ctx.SetNumberOfThreads(opts.NumberOfThreads)
 	ans := make([]*Match, len(items))
-	results := make(chan *Match, len(items))
 	nr := []rune(strings.ToLower(query))
 	if opts.Level1 == "" {
 		opts.Level1 = LEVEL1
@@ -219,15 +215,12 @@ func ScoreItems(query string, items []string, opts Options) []*Match {
 	ropts := resolved_options_type{
 		level1: []rune(opts.Level1), level2: []rune(opts.Level2), level3: []rune(opts.Level3),
 	}
-	ctx.Parallel(0, len(items), func(nums <-chan int) {
+	utils.Run_in_parallel_over_range(opts.NumberOfThreads, func(start, limit int) error {
 		w := workspace_type{}
-		for i := range nums {
-			results <- score_item(items[i], i, nr, &ropts, &w)
+		for i := start; i < limit; i++ {
+			ans[i] = score_item(items[i], i, nr, &ropts, &w)
 		}
-	})
-	close(results)
-	for x := range results {
-		ans[x.idx] = x
-	}
+		return nil
+	}, 0, len(items))
 	return ans
 }

tools/utils/misc.go

@@ -12,6 +12,7 @@ import (
 	"slices"
 	"strconv"
 	"strings"
+	"sync"
 
 	"golang.org/x/exp/constraints"
 )
@@ -86,6 +87,42 @@ func Format_stacktrace_on_panic(r any) (text string, err error) {
 	return strings.TrimSpace(text), err
 }
 
+// Run the specified function in parallel over chunks from the specified range.
+// If the function panics, it is turned into a regular error.
+func Run_in_parallel_over_range(num_procs int, f func(int, int) error, start, limit int) (err error) {
+	num_items := limit - start
+	if num_procs <= 0 {
+		num_procs = runtime.NumCPU()
+	}
+	num_procs = max(1, min(num_procs, num_items))
+	chunk_sz := max(1, num_items/num_procs)
+	var wg sync.WaitGroup
+	echan := make(chan error, num_procs)
+	for start < limit {
+		end := min(start+chunk_sz, limit)
+		wg.Add(1)
+		go func(start, end int) {
+			defer func() {
+				if r := recover(); r != nil {
+					stacktrace, e := Format_stacktrace_on_panic(r)
+					echan <- fmt.Errorf("%s\n\n%w", stacktrace, e)
+				}
+				wg.Done()
+			}()
+			if err := f(start, end); err != nil {
+				echan <- err
+			}
+		}(start, end)
+		start = end
+	}
+	wg.Wait()
+	close(echan)
+	for qerr := range echan {
+		return qerr
+	}
+	return
+
+}
 func Map[T any, O any](f func(x T) O, s []T) []O {
 	ans := make([]O, 0, len(s))
 	for _, x := range s {