From 48618cd5f00a6b38fb62d276d5c71c3b5a23ebdfbc9b83798ebcaacc3e8ab7df Mon Sep 17 00:00:00 2001
From: Sergey Matveev <stargrave@stargrave.org>
Date: Wed, 19 Feb 2025 17:55:27 +0300
Subject: [PATCH] Use half of cores by default

---
 go/cm/cmd/enctool/main.go            |  3 +--
 go/cm/cmd/hshtool/main.go            |  3 +--
 go/cm/hash/algo.go                   | 12 +++++++-----
 go/cm/sign/ed25519-blake2b/signer.go |  4 ++--
 go/cm/sign/gost/signer.go            |  4 ++--
 5 files changed, 13 insertions(+), 13 deletions(-)

diff --git a/go/cm/cmd/enctool/main.go b/go/cm/cmd/enctool/main.go
index 2eeceb5..a6e6ef2 100644
--- a/go/cm/cmd/enctool/main.go
+++ b/go/cm/cmd/enctool/main.go
@@ -27,7 +27,6 @@ import (
 	"io"
 	"log"
 	"os"
-	"runtime"
 	"strconv"
 
 	"github.com/companyzero/sntrup4591761"
@@ -152,7 +151,7 @@ func main() {
 	balloonT := flag.Int("balloon-t", 4, "Balloon's time cost")
 	balloonP := flag.Int("balloon-p", 2, "Balloon's number of threads")
 	doDecrypt := flag.Bool("d", false, "Decrypt")
-	parallel := flag.Int("parallel", runtime.NumCPU(), "Parallel cryptors")
+	parallel := flag.Int("parallel", cmhash.DefaultNumCPU, "Parallel cryptors")
 	noblob := flag.Bool("no-stream", false, "Include payload into container")
 	flag.Parse()
 
diff --git a/go/cm/cmd/hshtool/main.go b/go/cm/cmd/hshtool/main.go
index d43cc4b..adac9ef 100644
--- a/go/cm/cmd/hshtool/main.go
+++ b/go/cm/cmd/hshtool/main.go
@@ -6,7 +6,6 @@ import (
 	"fmt"
 	"log"
 	"os"
-	"runtime"
 
 	"go.cypherpunks.su/gogost/v6/gost34112012256"
 	"go.cypherpunks.su/gogost/v6/gost34112012512"
@@ -19,7 +18,7 @@ import (
 )
 
 func main() {
-	workers := flag.Int("p", runtime.NumCPU(), "Parallel workers")
+	workers := flag.Int("p", cmhash.DefaultNumCPU, "Parallel workers")
 	chunkLenK := flag.Int("c", merkle.DefaultChunkLen/1024, "Chunk size, KiB")
 	algo := flag.String("a", cmhash.BLAKE2bMerkle, "Algorithm to use")
 	list := flag.Bool("list", false, "List available algorithms")
diff --git a/go/cm/hash/algo.go b/go/cm/hash/algo.go
index 3942c7b..073f1dc 100644
--- a/go/cm/hash/algo.go
+++ b/go/cm/hash/algo.go
@@ -44,18 +44,20 @@ const (
 	Streebog512Merkle = "streebog512-merkle"
 )
 
+var DefaultNumCPU = max(1, runtime.NumCPU()/2)
+
 func ByName(name string) hash.Hash {
 	switch name {
 	case Streebog256, gost.GOST3410256A:
 		return gost34112012256.New()
 	case Streebog256Merkle, gost.GOST3410256AMerkle:
 		return gost.NewMerkleHasher(gost34112012256.New,
-			merkle.DefaultChunkLen, runtime.NumCPU())
+			merkle.DefaultChunkLen, DefaultNumCPU)
 	case Streebog512, gost.GOST3410512C:
 		return gost34112012512.New()
 	case Streebog512Merkle, gost.GOST3410512CMerkle:
 		return gost.NewMerkleHasher(gost34112012512.New,
-			merkle.DefaultChunkLen, runtime.NumCPU())
+			merkle.DefaultChunkLen, DefaultNumCPU)
 	case BLAKE2b, cmblake2b.Ed25519BLAKE2b, cmblake2b.Ed25519PhBLAKE2b:
 		h, err := blake2b.New512(nil)
 		if err != nil {
@@ -64,7 +66,7 @@ func ByName(name string) hash.Hash {
 		return h
 	case BLAKE2bMerkle, cmblake2b.Ed25519PhBLAKE2bMerkle:
 		return cmblake2b.NewMerkleHasher(
-			merkle.DefaultChunkLen, runtime.NumCPU())
+			merkle.DefaultChunkLen, DefaultNumCPU)
 	case BLAKE2b256:
 		h, err := blake2b.New256(nil)
 		if err != nil {
@@ -77,10 +79,10 @@ func ByName(name string) hash.Hash {
 		return NewSHAKE256()
 	case SHAKE128Merkle:
 		return NewSHAKE128MerkleHasher(
-			merkle.DefaultChunkLen, runtime.NumCPU())
+			merkle.DefaultChunkLen, DefaultNumCPU)
 	case SHAKE256Merkle:
 		return NewSHAKE256MerkleHasher(
-			merkle.DefaultChunkLen, runtime.NumCPU())
+			merkle.DefaultChunkLen, DefaultNumCPU)
 	}
 	return nil
 }
diff --git a/go/cm/sign/ed25519-blake2b/signer.go b/go/cm/sign/ed25519-blake2b/signer.go
index 001ab45..8e992a7 100644
--- a/go/cm/sign/ed25519-blake2b/signer.go
+++ b/go/cm/sign/ed25519-blake2b/signer.go
@@ -20,8 +20,8 @@ import (
 	"errors"
 	"hash"
 	"io"
-	"runtime"
 
+	cmhash "go.cypherpunks.su/keks/cm/hash"
 	cmblake2b "go.cypherpunks.su/keks/cm/hash/blake2b"
 	"go.cypherpunks.su/keks/cm/hash/merkle"
 	"go.cypherpunks.su/keks/cm/sign/ed25519-blake2b/ed25519"
@@ -50,7 +50,7 @@ func (s *Signer) SetMode(m mode.Mode) error {
 		return nil
 	case mode.Merkle:
 		s.mode = m
-		h := cmblake2b.NewMerkleHasher(merkle.DefaultChunkLen, runtime.NumCPU())
+		h := cmblake2b.NewMerkleHasher(merkle.DefaultChunkLen, cmhash.DefaultNumCPU)
 		s.prehasher = &h
 		return nil
 	default:
diff --git a/go/cm/sign/gost/signer.go b/go/cm/sign/gost/signer.go
index 99a3a3e..27ad00e 100644
--- a/go/cm/sign/gost/signer.go
+++ b/go/cm/sign/gost/signer.go
@@ -20,12 +20,12 @@ import (
 	"errors"
 	"hash"
 	"io"
-	"runtime"
 
 	"go.cypherpunks.su/gogost/v6/gost3410"
 	"go.cypherpunks.su/gogost/v6/gost34112012256"
 	"go.cypherpunks.su/gogost/v6/gost34112012512"
 
+	cmhash "go.cypherpunks.su/keks/cm/hash"
 	hashgost "go.cypherpunks.su/keks/cm/hash/gost"
 	"go.cypherpunks.su/keks/cm/hash/merkle"
 	"go.cypherpunks.su/keks/cm/sign/mode"
@@ -50,7 +50,7 @@ func (s *Signer) SetMode(m mode.Mode) error {
 		return nil
 	case mode.Merkle:
 		s.mode = m
-		p := hashgost.NewMerkleHasher(s.NewHasher, merkle.DefaultChunkLen, runtime.NumCPU())
+		p := hashgost.NewMerkleHasher(s.NewHasher, merkle.DefaultChunkLen, cmhash.DefaultNumCPU)
 		s.prehasher = &p
 		return nil
 	default:
-- 
2.48.1