Merge pull request #5519 from martin-frbg/issue5517

Introduce a minimum problem size requirement for multithreading in the hermitian operations

Author: martin-frbg

interface/zher.c

@@ -177,7 +177,10 @@ void CNAME(enum CBLAS_ORDER order, enum CBLAS_UPLO Uplo, blasint n, FLOAT alpha,
   buffer = (FLOAT *)blas_memory_alloc(1);
 
 #ifdef SMP
-  nthreads = num_cpu_avail(2);
+  if (n < 100)
+    nthreads = 1;
+  else
+    nthreads = num_cpu_avail(2);
 
   if (nthreads == 1) {
 #endif

interface/zher2.c

@@ -186,7 +186,10 @@ void CNAME(enum CBLAS_ORDER order, enum CBLAS_UPLO Uplo, blasint n, void *VALPHA
   buffer = (FLOAT *)blas_memory_alloc(1);
 
 #ifdef SMP
-  nthreads = num_cpu_avail(2);
+  if (n < 100)
+	nthreads = 1;
+  else
+    nthreads = num_cpu_avail(2);
 
   if (nthreads == 1) {
 #endif

interface/zhpr.c

@@ -175,7 +175,10 @@ void CNAME(enum CBLAS_ORDER order,
   buffer = (FLOAT *)blas_memory_alloc(1);
 
 #ifdef SMP
-  nthreads = num_cpu_avail(2);
+  if (n < 100)
+    nthreads = 1;
+  else
+    nthreads = num_cpu_avail(2);
 
   if (nthreads == 1) {
 #endif

interface/zhpr2.c

@@ -187,7 +187,10 @@ void CNAME(enum CBLAS_ORDER order,
   buffer = (FLOAT *)blas_memory_alloc(1);
 
 #ifdef SMP
-  nthreads = num_cpu_avail(2);
+  if (n < 100)
+	nthreads = 1;
+  else
+    nthreads = num_cpu_avail(2);
 
   if (nthreads == 1) {
 #endif