From 2957281275810ab8bc87304134552cdd046216f2 Mon Sep 17 00:00:00 2001
From: Martin Kroeker <martin@ruby.chemie.uni-freiburg.de>
Date: Tue, 14 May 2024 18:59:21 +0200
Subject: [PATCH] Introduce a lower limit for multithreading

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

diff --git a/interface/zgbmv.c b/interface/zgbmv.c
index 5e275a8ed..5128b22e1 100644
--- a/interface/zgbmv.c
+++ b/interface/zgbmv.c
@@ -251,7 +251,10 @@ void CNAME(enum CBLAS_ORDER order,
   buffer = (FLOAT *)blas_memory_alloc(1);
 
 #ifdef SMP
-  nthreads = num_cpu_avail(2);
+  if (m * n  < 125000 || ku + kl < 15) 
+    nthreads = 1;
+  else
+    nthreads = num_cpu_avail(2);
 
   if (nthreads == 1) {
 #endif