From d5760f310ccdf7aeb8b30ad6fe5973da10c6b1d2 Mon Sep 17 00:00:00 2001
From: conrad <conrad@localhost.localdomain>
Date: Mon, 9 May 2022 14:56:37 +1000
Subject: [PATCH] more efficient handling of aliasing in default case

---
 include/armadillo_bits/glue_solve_meat.hpp | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/include/armadillo_bits/glue_solve_meat.hpp b/include/armadillo_bits/glue_solve_meat.hpp
index d429558d..54adfa8b 100644
--- a/include/armadillo_bits/glue_solve_meat.hpp
+++ b/include/armadillo_bits/glue_solve_meat.hpp
@@ -117,7 +117,18 @@ glue_solve_gen_full::apply(Mat<eT>& actual_out, const Base<eT,T1>& A_expr, const
   arma_debug_check( (fast     && refine      ), "solve(): options 'fast' and 'refine' are mutually exclusive"           );
   arma_debug_check( (no_sympd && likely_sympd), "solve(): options 'no_sympd' and 'likely_sympd' are mutually exclusive" );
   
-  Mat<eT> out;
+  bool is_alias = true;
+  
+  if(is_Mat<T1>::value && is_Mat<T2>::value)
+    {
+    const quasi_unwrap<T1> UA( A_expr.get_ref() );
+    const quasi_unwrap<T2> UB( B_expr.get_ref() );
+    
+    if( (UA.is_alias(actual_out) == false) && (UB.is_alias(actual_out) == false) )  { is_alias = false; }
+    }
+  
+  Mat<eT>  tmp;
+  Mat<eT>& out = (is_alias) ? tmp : actual_out;
   
   Mat<eT> A = A_expr.get_ref();
   
@@ -329,7 +340,7 @@ glue_solve_gen_full::apply(Mat<eT>& actual_out, const Base<eT,T1>& A_expr, const
     status = auxlib::solve_approx_svd(out, A, B_expr.get_ref());  // A is overwritten
     }
   
-  actual_out.steal_mem(out);
+  if(is_alias)  { actual_out.steal_mem(out); }
   
   return status;
   }