From 451d5d2cecc08bc9e308d4d4a06a43d124664320 Mon Sep 17 00:00:00 2001
From: conrad <conrad@localhost.localdomain>
Date: Thu, 5 Mar 2026 15:50:01 +1000
Subject: [PATCH] speedups for empty submatrices

---
 include/armadillo_bits/op_accu_meat.hpp      | 8 ++++++++
 include/armadillo_bits/op_vectorise_meat.hpp | 8 ++++++++
 2 files changed, 16 insertions(+)

diff --git a/include/armadillo_bits/op_accu_meat.hpp b/include/armadillo_bits/op_accu_meat.hpp
index 3cd71064..c770dd84 100644
--- a/include/armadillo_bits/op_accu_meat.hpp
+++ b/include/armadillo_bits/op_accu_meat.hpp
@@ -80,6 +80,8 @@ op_accu_mat::apply_proxy_at(const Proxy<T1>& P)
   const uword n_rows = P.get_n_rows();
   const uword n_cols = P.get_n_cols();
   
+  if( (n_rows == 0) || (n_cols == 0) )  { return eT(0); }
+  
   eT val = eT(0);
   
   if(n_rows != 1)
@@ -146,6 +148,8 @@ op_accu_mat::apply_omit_helper(const Proxy<T1>& P, functor is_omitted)
     const uword n_rows = P.get_n_rows();
     const uword n_cols = P.get_n_cols();
     
+    if( (n_rows == 0) || (n_cols == 0) )  { return eT_zero; }
+    
     for(uword c=0; c < n_cols; ++c)
     for(uword r=0; r < n_rows; ++r)
       {
@@ -602,6 +606,8 @@ op_accu_mat::apply(const subview<eT>& X)
   const uword X_n_rows = X.n_rows;
   const uword X_n_cols = X.n_cols;
   
+  if( (X_n_rows == 0) || (X_n_cols == 0) )  { return eT(0); }
+  
   if(X_n_rows == 1)
     {
     const uword X_m_n_rows = X.m.n_rows;
@@ -750,6 +756,8 @@ op_accu_cube::apply_proxy_at(const ProxyCube<T1>& P)
   const uword n_cols   = P.get_n_cols();
   const uword n_slices = P.get_n_slices();
   
+  if( (n_rows == 0) || (n_cols == 0) || (n_slices == 0) )  { return eT(0); }
+  
   eT val1 = eT(0);
   eT val2 = eT(0);
   
diff --git a/include/armadillo_bits/op_vectorise_meat.hpp b/include/armadillo_bits/op_vectorise_meat.hpp
index 724ce50c..f185ac4c 100644
--- a/include/armadillo_bits/op_vectorise_meat.hpp
+++ b/include/armadillo_bits/op_vectorise_meat.hpp
@@ -176,6 +176,8 @@ op_vectorise_col::apply_subview(Mat<eT>& out, const subview<eT>& sv)
   
   out.set_size(sv.n_elem, 1);
   
+  if(sv.n_elem == 0)  { return; }
+  
   eT* out_mem = out.memptr();
   
   for(uword col=0; col < sv_n_cols; ++col)
@@ -201,6 +203,8 @@ op_vectorise_col::apply_proxy(Mat<typename T1::elem_type>& out, const Proxy<T1>&
   
   out.set_size(N, 1);
   
+  if(N == 0)  { return; }
+  
   eT* outmem = out.memptr();
   
   if(Proxy<T1>::use_at == false)
@@ -305,6 +309,8 @@ op_vectorise_row::apply_proxy(Mat<typename T1::elem_type>& out, const Proxy<T1>&
   
   out.set_size(1, n_elem);
   
+  if(n_elem == 0)  { return; }
+  
   eT* outmem = out.memptr();
   
   if(n_cols == 1)
@@ -471,6 +477,8 @@ op_vectorise_cube_col::apply_proxy(Mat<typename T1::elem_type>& out, const T1& e
   
   out.set_size(N, 1);
   
+  if(N == 0)  { return; }
+  
   eT* outmem = out.memptr();
   
   if(ProxyCube<T1>::use_at == false)