From 30d80db02d23daa8286ade2e498d65de1e23d006 Mon Sep 17 00:00:00 2001
From: Eric Coissac <eric.coissac@metabarcoding.org>
Date: Sun, 6 Feb 2022 18:52:53 +0100
Subject: [PATCH] All an option to limit number of CPU

---
 pkg/obioptions/options.go | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/pkg/obioptions/options.go b/pkg/obioptions/options.go
index 685ed58..bba7f6d 100644
--- a/pkg/obioptions/options.go
+++ b/pkg/obioptions/options.go
@@ -2,6 +2,7 @@ package obioptions
 
 import (
 	"fmt"
+	"log"
 	"os"
 	"runtime"
 
@@ -10,6 +11,7 @@ import (
 
 var _Debug = false
 var _ParallelWorkers = runtime.NumCPU() - 1
+var _MaxAllowedCPU = runtime.NumCPU()
 var _BufferSize = 1
 var _BatchSize = 5000
 
@@ -20,7 +22,11 @@ func GenerateOptionParser(optionset ...func(*getoptions.GetOpt)) ArgumentParser
 	options.Bool("help", false, options.Alias("h", "?"))
 	options.BoolVar(&_Debug, "debug", false)
 
-	options.IntVar(&_ParallelWorkers, "workers", runtime.NumCPU()-1,
+	options.IntVar(&_ParallelWorkers, "workers", _ParallelWorkers,
+		options.Alias("w"),
+		options.Description("Number of parallele threads computing the result"))
+
+	options.IntVar(&_MaxAllowedCPU, "max-cpu", _MaxAllowedCPU,
 		options.Alias("w"),
 		options.Description("Number of parallele threads computing the result"))
 
@@ -32,6 +38,12 @@ func GenerateOptionParser(optionset ...func(*getoptions.GetOpt)) ArgumentParser
 
 		remaining, err := options.Parse(args[1:])
 
+		// Setup the maximum number of CPU usable by the program
+		runtime.GOMAXPROCS(_MaxAllowedCPU)
+		if options.Called("max-cpu") {
+			log.Printf("CPU number limited to %d", _MaxAllowedCPU)
+		}
+
 		if options.Called("help") {
 			fmt.Fprint(os.Stderr, options.Help())
 			os.Exit(1)
@@ -51,6 +63,12 @@ func CLIParallelWorkers() int {
 	return _ParallelWorkers
 }
 
+// CLIParallelWorkers returns the number of parallel workers requested by
+// the command line option --workers|-w.
+func CLIMaxCPU() int {
+	return _MaxAllowedCPU
+}
+
 // CLIBufferSize returns the expeted channel buffer size for obitools
 func CLIBufferSize() int {
 	return _BufferSize