From 5fd871d7eabdb5e33f5d2ef81455ecac4ac098ab Mon Sep 17 00:00:00 2001
From: Martin Kroeker <martin@ruby.chemie.uni-freiburg.de>
Date: Tue, 14 May 2024 18:48:03 +0200
Subject: [PATCH] Introduce a lower limit for multithreading

---
 interface/gbmv.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/interface/gbmv.c b/interface/gbmv.c
index 1d58ba807..7a6581368 100644
--- a/interface/gbmv.c
+++ b/interface/gbmv.c
@@ -227,7 +227,10 @@ void CNAME(enum CBLAS_ORDER order,
   buffer = (FLOAT *)blas_memory_alloc(1);
 
 #ifdef SMP
-  nthreads = num_cpu_avail(2);
+  if (m * n < 250000 || kl+ku < 15 )
+    nthreads = 1;
+  else
+    nthreads = num_cpu_avail(2);
 
   if (nthreads == 1) {
 #endif