From 51413925bdcc1fceec46e58acbd7cf03b7762aa1 Mon Sep 17 00:00:00 2001
From: wernsaar <wernsaar@googlemail.com>
Date: Tue, 15 Jul 2014 16:27:02 +0200
Subject: [PATCH] adjust number of threads for small size in cgemv and zgemv

---
 interface/zgemv.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/interface/zgemv.c b/interface/zgemv.c
index fcc2fda54..50513a8e4 100644
--- a/interface/zgemv.c
+++ b/interface/zgemv.c
@@ -233,7 +233,19 @@ void CNAME(enum CBLAS_ORDER order,
   buffer = (FLOAT *)blas_memory_alloc(1);
 
 #ifdef SMP
-  nthreads = num_cpu_avail(2);
+
+  int  nthreads_max = num_cpu_avail(2);
+  int  nthreads_avail = nthreads_max;
+
+  double MNK = (double) m * (double) n;
+  if ( MNK <= (80.0 * 20.0  * (double) GEMM_MULTITHREAD_THRESHOLD)  )
+        nthreads_max = 1;
+
+  if ( nthreads_max > nthreads_avail )
+        nthreads = nthreads_avail;
+  else
+        nthreads = nthreads_max;
+
 
   if (nthreads == 1) {
 #endif