From c0c2dadbd9114552727c2de7d063834f6c82a121 Mon Sep 17 00:00:00 2001
From: Julien Schueller <schueller@phimeca.com>
Date: Mon, 29 Jun 2026 17:23:43 +0200
Subject: [PATCH 1/2] lapack: fix missing thread caps

---
 interface/lapack/getrs.c  | 6 +++++-
 interface/lapack/laed3.c  | 3 ++-
 interface/lapack/laswp.c  | 6 +++++-
 interface/lapack/lauum.c  | 6 +++++-
 interface/lapack/trtrs.c  | 6 +++++-
 interface/lapack/zgetrs.c | 6 +++++-
 interface/lapack/zlaswp.c | 6 +++++-
 interface/lapack/zlauum.c | 6 +++++-
 interface/lapack/ztrtri.c | 6 +++++-
 interface/lapack/ztrtrs.c | 6 +++++-
 10 files changed, 47 insertions(+), 10 deletions(-)

diff --git a/interface/lapack/getrs.c b/interface/lapack/getrs.c
index c2a9eb882f..0cc6df0371 100644
--- a/interface/lapack/getrs.c
+++ b/interface/lapack/getrs.c
@@ -126,7 +126,11 @@ int NAME(char *TRANS, blasint *N, blasint *NRHS, FLOAT *a, blasint *ldA,
 
 #ifdef SMP
   args.common = NULL;
-  args.nthreads = num_cpu_avail(4);
+  if (args.m < 64) {
+    args.nthreads = 1;
+  } else {
+    args.nthreads = num_cpu_avail(4);
+  }
 
   if (args.nthreads == 1) {
 #endif
diff --git a/interface/lapack/laed3.c b/interface/lapack/laed3.c
index 4e5215fcf7..bf3198bc03 100644
--- a/interface/lapack/laed3.c
+++ b/interface/lapack/laed3.c
@@ -72,7 +72,8 @@ int NAME(blasint *k, blasint *n, blasint *n1, FLOAT *d,
   if (kval == 0) return 0;
 
 #ifdef SMP
-  int nthreads = num_cpu_avail(4);
+  int nthreads = 1;
+  if (n >= 64) nthreads = num_cpu_avail(4);
 
   if (nthreads == 1) {
 #endif
diff --git a/interface/lapack/laswp.c b/interface/lapack/laswp.c
index 6544dbc5b2..698e39a99f 100644
--- a/interface/lapack/laswp.c
+++ b/interface/lapack/laswp.c
@@ -77,7 +77,11 @@ int NAME(blasint *N, FLOAT *a, blasint *LDA, blasint *K1, blasint *K2, blasint *
   flag = (incx < 0);
 
 #ifdef SMP
-  nthreads = num_cpu_avail(1);
+  if (n < 64) {
+    nthreads = 1;
+  } else {
+    nthreads = num_cpu_avail(1);
+  }
 
   if (nthreads == 1) {
 #endif
diff --git a/interface/lapack/lauum.c b/interface/lapack/lauum.c
index 70f6a0ec54..81c4fc07aa 100644
--- a/interface/lapack/lauum.c
+++ b/interface/lapack/lauum.c
@@ -112,7 +112,11 @@ int NAME(char *UPLO, blasint *N, FLOAT *a, blasint *ldA, blasint *Info){
 
 #ifdef SMP
   args.common = NULL;
-  args.nthreads = num_cpu_avail(4);
+  if (args.n < 64) {
+    args.nthreads = 1;
+  } else {
+    args.nthreads = num_cpu_avail(4);
+  }
 
   if (args.nthreads == 1) {
 #endif
diff --git a/interface/lapack/trtrs.c b/interface/lapack/trtrs.c
index 3cc449318f..53d8fb0ec3 100644
--- a/interface/lapack/trtrs.c
+++ b/interface/lapack/trtrs.c
@@ -147,7 +147,11 @@ int NAME(char *UPLO, char* TRANS, char* DIAG, blasint *N, blasint *NRHS, FLOAT *
 
 #ifdef SMP
   args.common = NULL;
-  args.nthreads = num_cpu_avail(4);
+  if (args.m < 64) {
+    args.nthreads = 1;
+  } else {
+    args.nthreads = num_cpu_avail(4);
+  }
 
   if (args.nthreads == 1) {
 #endif
diff --git a/interface/lapack/zgetrs.c b/interface/lapack/zgetrs.c
index 0add909ca4..e76a8a1b24 100644
--- a/interface/lapack/zgetrs.c
+++ b/interface/lapack/zgetrs.c
@@ -125,7 +125,11 @@ int NAME(char *TRANS, blasint *N, blasint *NRHS, FLOAT *a, blasint *ldA,
 #endif
 
 #ifdef SMP
-  args.nthreads = num_cpu_avail(4);
+  if (args.m < 64) {
+    args.nthreads = 1;
+  } else {
+    args.nthreads = num_cpu_avail(4);
+  }
 
   if (args.nthreads == 1) {
 #endif
diff --git a/interface/lapack/zlaswp.c b/interface/lapack/zlaswp.c
index 7bb4a659ea..c5188cdf77 100644
--- a/interface/lapack/zlaswp.c
+++ b/interface/lapack/zlaswp.c
@@ -78,7 +78,11 @@ int NAME(blasint *N, FLOAT *a, blasint *LDA, blasint *K1, blasint *K2, blasint *
   flag = (incx < 0);
 
 #ifdef SMP
-  nthreads = num_cpu_avail(2);
+  if (n < 64) {
+    nthreads = 1;
+  } else {
+    nthreads = num_cpu_avail(2);
+  }
 
   if (nthreads == 1) {
 #endif
diff --git a/interface/lapack/zlauum.c b/interface/lapack/zlauum.c
index 4a36cc1733..9f0cd94001 100644
--- a/interface/lapack/zlauum.c
+++ b/interface/lapack/zlauum.c
@@ -112,7 +112,11 @@ int NAME(char *UPLO, blasint *N, FLOAT *a, blasint *ldA, blasint *Info){
 
 #ifdef SMP
   args.common = NULL;
-  args.nthreads = num_cpu_avail(4);
+  if (args.n < 64) {
+    args.nthreads = 1;
+  } else {
+    args.nthreads = num_cpu_avail(4);
+  }
 
   if (args.nthreads == 1) {
 #endif
diff --git a/interface/lapack/ztrtri.c b/interface/lapack/ztrtri.c
index dda4a9e4b6..bfd6e3ea9d 100644
--- a/interface/lapack/ztrtri.c
+++ b/interface/lapack/ztrtri.c
@@ -125,7 +125,11 @@ int NAME(char *UPLO, char *DIAG, blasint *N, FLOAT *a, blasint *ldA, blasint *In
 
 #ifdef SMP
   args.common = NULL;
-  args.nthreads = num_cpu_avail(4);
+  if (args.n < 64) {
+    args.nthreads = 1;
+  } else {
+    args.nthreads = num_cpu_avail(4);
+  }
 
   if (args.nthreads == 1) {
 #endif
diff --git a/interface/lapack/ztrtrs.c b/interface/lapack/ztrtrs.c
index ec3343393a..df0bac360a 100644
--- a/interface/lapack/ztrtrs.c
+++ b/interface/lapack/ztrtrs.c
@@ -147,7 +147,11 @@ int NAME(char *UPLO, char* TRANS, char* DIAG, blasint *N, blasint *NRHS, FLOAT *
 
 #ifdef SMP
   args.common = NULL;
-  args.nthreads = num_cpu_avail(4);
+  if (args.m < 64) {
+    args.nthreads = 1;
+  } else {
+    args.nthreads = num_cpu_avail(4);
+  }
 
   if (args.nthreads == 1) {
 #endif

From 5010c0abb8976e6c0fdba019efeb32713fdf2883 Mon Sep 17 00:00:00 2001
From: Julien Schueller <schueller@phimeca.com>
Date: Mon, 29 Jun 2026 17:23:55 +0200
Subject: [PATCH 2/2] blas: fix missing thread caps

---
 interface/spr.c   | 3 +++
 interface/spr2.c  | 3 +++
 interface/syr.c   | 3 +++
 interface/syr2.c  | 3 +++
 interface/tbmv.c  | 3 +++
 interface/tpmv.c  | 3 +++
 interface/zhpmv.c | 3 +++
 interface/zspr.c  | 3 +++
 interface/zspr2.c | 3 +++
 interface/zsymv.c | 3 +++
 interface/zsyr.c  | 3 +++
 interface/zsyr2.c | 3 +++
 interface/ztbmv.c | 3 +++
 interface/ztpmv.c | 3 +++
 14 files changed, 42 insertions(+)

diff --git a/interface/spr.c b/interface/spr.c
index 8aafc9f857..1f5e0bd31a 100644
--- a/interface/spr.c
+++ b/interface/spr.c
@@ -194,6 +194,9 @@ void CNAME(enum CBLAS_ORDER order,
 #ifdef SMP
   nthreads = num_cpu_avail(2);
 
+  if (n < 50) nthreads = 1;
+  if (nthreads > 2 && n < 500) nthreads = 2;
+
   if (nthreads == 1) {
 #endif
 
diff --git a/interface/spr2.c b/interface/spr2.c
index b5aab1767d..fb1b338f2b 100644
--- a/interface/spr2.c
+++ b/interface/spr2.c
@@ -198,6 +198,9 @@ void CNAME(enum CBLAS_ORDER order,
 #ifdef SMP
   nthreads = num_cpu_avail(2);
 
+  if (n < 50) nthreads = 1;
+  if (nthreads > 2 && n < 500) nthreads = 2;
+
   if (nthreads == 1) {
 #endif
 
diff --git a/interface/syr.c b/interface/syr.c
index ad75264b1f..761df762af 100644
--- a/interface/syr.c
+++ b/interface/syr.c
@@ -197,6 +197,9 @@ void CNAME(enum CBLAS_ORDER order, enum CBLAS_UPLO Uplo, blasint n, FLOAT alpha,
 #ifdef SMP
   nthreads = num_cpu_avail(2);
 
+  if (n < 50) nthreads = 1;
+  if (nthreads > 2 && n < 500) nthreads = 2;
+
   if (nthreads == 1) {
 #endif
 
diff --git a/interface/syr2.c b/interface/syr2.c
index 632906d288..b983fa0d6e 100644
--- a/interface/syr2.c
+++ b/interface/syr2.c
@@ -199,6 +199,9 @@ void CNAME(enum CBLAS_ORDER order, enum CBLAS_UPLO Uplo, blasint n, FLOAT alpha,
 #ifdef SMP
   nthreads = num_cpu_avail(2);
 
+  if (n < 50) nthreads = 1;
+  if (nthreads > 2 && n < 500) nthreads = 2;
+
   if (nthreads == 1) {
 #endif
 
diff --git a/interface/tbmv.c b/interface/tbmv.c
index b5f3ab740d..c518c296a0 100644
--- a/interface/tbmv.c
+++ b/interface/tbmv.c
@@ -225,6 +225,9 @@ void CNAME(enum CBLAS_ORDER order, enum CBLAS_UPLO Uplo,
 #ifdef SMP
   nthreads = num_cpu_avail(2);
 
+  if (n < 50) nthreads = 1;
+  if (nthreads > 2 && n < 500) nthreads = 2;
+
   if (nthreads == 1) {
 #endif
 
diff --git a/interface/tpmv.c b/interface/tpmv.c
index 262af2285d..c9ad3748ad 100644
--- a/interface/tpmv.c
+++ b/interface/tpmv.c
@@ -223,6 +223,9 @@ void CNAME(enum CBLAS_ORDER order, enum CBLAS_UPLO Uplo,
 #ifdef SMP
   nthreads = num_cpu_avail(2);
 
+  if (n < 50) nthreads = 1;
+  if (nthreads > 2 && n < 500) nthreads = 2;
+
   if (nthreads == 1) {
 #endif
 
diff --git a/interface/zhpmv.c b/interface/zhpmv.c
index ff49716b54..013dd3e795 100644
--- a/interface/zhpmv.c
+++ b/interface/zhpmv.c
@@ -196,6 +196,9 @@ void CNAME(enum CBLAS_ORDER order,
 #ifdef SMP
   nthreads = num_cpu_avail(2);
 
+  if (n < 50) nthreads = 1;
+  if (nthreads > 2 && n < 500) nthreads = 2;
+
   if (nthreads == 1) {
 #endif
 
diff --git a/interface/zspr.c b/interface/zspr.c
index 574b59aa28..190e62d668 100644
--- a/interface/zspr.c
+++ b/interface/zspr.c
@@ -123,6 +123,9 @@ void NAME(char *UPLO, blasint *N, FLOAT  *ALPHA,
 #ifdef SMP
   nthreads = num_cpu_avail(2);
 
+  if (n < 50) nthreads = 1;
+  if (nthreads > 2 && n < 500) nthreads = 2;
+
   if (nthreads == 1) {
 #endif
 
diff --git a/interface/zspr2.c b/interface/zspr2.c
index 44c36d5536..53b7b98676 100644
--- a/interface/zspr2.c
+++ b/interface/zspr2.c
@@ -126,6 +126,9 @@ void NAME(char *UPLO, blasint *N, FLOAT  *ALPHA,
 #ifdef SMP
   nthreads = num_cpu_avail(2);
 
+  if (n < 50) nthreads = 1;
+  if (nthreads > 2 && n < 500) nthreads = 2;
+
   if (nthreads == 1) {
 #endif
 
diff --git a/interface/zsymv.c b/interface/zsymv.c
index 1d6ff1f348..0cd690f812 100644
--- a/interface/zsymv.c
+++ b/interface/zsymv.c
@@ -120,6 +120,9 @@ void NAME(char *UPLO, blasint *N, FLOAT  *ALPHA, FLOAT *a, blasint *LDA,
 #ifdef SMP
   nthreads = num_cpu_avail(2);
 
+  if (n < 50) nthreads = 1;
+  if (nthreads > 2 && n < 500) nthreads = 2;
+
   if (nthreads == 1) {
 #endif
 
diff --git a/interface/zsyr.c b/interface/zsyr.c
index 51cca84ee6..0d3c35dc03 100644
--- a/interface/zsyr.c
+++ b/interface/zsyr.c
@@ -208,6 +208,9 @@ void CNAME(enum CBLAS_ORDER order, enum CBLAS_UPLO Uplo, int n, void* valpha, FL
 #ifdef SMP
   nthreads = num_cpu_avail(2);
 
+  if (n < 50) nthreads = 1;
+  if (nthreads > 2 && n < 500) nthreads = 2;
+
   if (nthreads == 1) {
 #endif
 
diff --git a/interface/zsyr2.c b/interface/zsyr2.c
index 7c81c20930..e3bdf56e2b 100644
--- a/interface/zsyr2.c
+++ b/interface/zsyr2.c
@@ -128,6 +128,9 @@ void NAME(char *UPLO, blasint *N, FLOAT  *ALPHA,
 #ifdef SMP
   nthreads = num_cpu_avail(2);
 
+  if (n < 50) nthreads = 1;
+  if (nthreads > 2 && n < 500) nthreads = 2;
+
   if (nthreads == 1) {
 #endif
 
diff --git a/interface/ztbmv.c b/interface/ztbmv.c
index d56620c5bc..98fce6606d 100644
--- a/interface/ztbmv.c
+++ b/interface/ztbmv.c
@@ -240,6 +240,9 @@ void CNAME(enum CBLAS_ORDER order, enum CBLAS_UPLO Uplo,
 #ifdef SMP
   nthreads = num_cpu_avail(2);
 
+  if (n < 50) nthreads = 1;
+  if (nthreads > 2 && n < 500) nthreads = 2;
+
   if (nthreads == 1) {
 #endif
 
diff --git a/interface/ztpmv.c b/interface/ztpmv.c
index 3791d16026..3d79e84e1f 100644
--- a/interface/ztpmv.c
+++ b/interface/ztpmv.c
@@ -231,6 +231,9 @@ void CNAME(enum CBLAS_ORDER order, enum CBLAS_UPLO Uplo,
 #ifdef SMP
   nthreads = num_cpu_avail(2);
 
+  if (n < 50) nthreads = 1;
+  if (nthreads > 2 && n < 500) nthreads = 2;
+
   if (nthreads == 1) {
 #endif