From 197b9ffc3e82e7485625a2d3ff9f63f5d8b5bb45 Mon Sep 17 00:00:00 2001
From: Sam Mish <samuelpmish@gmail.com>
Date: Mon, 5 Aug 2024 10:30:19 -0700
Subject: [PATCH 1/3] defer initialization of sparse matrix LUTs to when
 they're requested, rather than eagerly evaluating

---
 src/serac/numerics/functional/dof_numbering.hpp | 12 ++++++++++--
 src/serac/numerics/functional/functional.hpp    |  5 ++++-
 2 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/src/serac/numerics/functional/dof_numbering.hpp b/src/serac/numerics/functional/dof_numbering.hpp
index 8dce4e5f19..87a5b954d8 100644
--- a/src/serac/numerics/functional/dof_numbering.hpp
+++ b/src/serac/numerics/functional/dof_numbering.hpp
@@ -276,6 +276,9 @@ struct GradientAssemblyLookupTables {
       }
     };
   };
+  
+  /// dummy default ctor to enable deferred initialization
+  GradientAssemblyLookupTables() : initialized{false} {}; 
 
   /**
    * @param block_test_dofs object containing information about dofs for the test space
@@ -284,8 +287,8 @@ struct GradientAssemblyLookupTables {
    * @brief create lookup tables describing which degrees of freedom
    * correspond to each domain/boundary element
    */
-  GradientAssemblyLookupTables(const serac::BlockElementRestriction& block_test_dofs,
-                               const serac::BlockElementRestriction& block_trial_dofs)
+  void init(const serac::BlockElementRestriction& block_test_dofs,
+            const serac::BlockElementRestriction& block_trial_dofs)
   {
     // we start by having each element and boundary element emit the (i,j) entry that it
     // touches in the global "stiffness matrix", and also keep track of some metadata about
@@ -342,6 +345,8 @@ struct GradientAssemblyLookupTables {
     }
 
     row_ptr.back() = static_cast<int>(nnz);
+
+    initialized = true;
   }
 
   /**
@@ -368,6 +373,9 @@ struct GradientAssemblyLookupTables {
    * corresponding to the (i,j) entry
    */
   std::unordered_map<Entry, uint32_t, Entry::Hasher> nz_LUT;
+
+  bool initialized;
+
 };
 
 }  // namespace serac
diff --git a/src/serac/numerics/functional/functional.hpp b/src/serac/numerics/functional/functional.hpp
index 9930b3b84a..8f32a3096b 100644
--- a/src/serac/numerics/functional/functional.hpp
+++ b/src/serac/numerics/functional/functional.hpp
@@ -537,7 +537,6 @@ class Functional<test(trials...), exec> {
     Gradient(Functional<test(trials...), exec>& f, uint32_t which = 0)
         : mfem::Operator(f.test_space_->GetTrueVSize(), f.trial_space_[which]->GetTrueVSize()),
           form_(f),
-          lookup_tables(f.G_test_[Domain::Type::Elements], f.G_trial_[Domain::Type::Elements][which]),
           which_argument(which),
           test_space_(f.test_space_),
           trial_space_(f.trial_space_[which]),
@@ -575,6 +574,10 @@ class Functional<test(trials...), exec> {
 
       constexpr bool col_ind_is_sorted = true;
 
+      if (!lookup_tables.initialized) {
+        lookup_tables.init(form_.G_test_[Domain::Type::Elements], form_.G_trial_[Domain::Type::Elements][which_argument]);
+      }
+
       double* values = new double[lookup_tables.nnz]{};
 
       std::map<mfem::Geometry::Type, ExecArray<double, 3, exec>> element_gradients[Domain::num_types];

From 1169b6e53b5dd4808a43562f6f54b3e5c682b3d6 Mon Sep 17 00:00:00 2001
From: Michael Tupek <tupek2@llnl.gov>
Date: Mon, 5 Aug 2024 13:18:12 -0700
Subject: [PATCH 2/3] Fix style.

---
 src/serac/numerics/functional/dof_numbering.hpp | 5 ++---
 src/serac/numerics/functional/functional.hpp    | 3 ++-
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/serac/numerics/functional/dof_numbering.hpp b/src/serac/numerics/functional/dof_numbering.hpp
index 87a5b954d8..39c671f617 100644
--- a/src/serac/numerics/functional/dof_numbering.hpp
+++ b/src/serac/numerics/functional/dof_numbering.hpp
@@ -276,9 +276,9 @@ struct GradientAssemblyLookupTables {
       }
     };
   };
-  
+
   /// dummy default ctor to enable deferred initialization
-  GradientAssemblyLookupTables() : initialized{false} {}; 
+  GradientAssemblyLookupTables() : initialized{false} {};
 
   /**
    * @param block_test_dofs object containing information about dofs for the test space
@@ -375,7 +375,6 @@ struct GradientAssemblyLookupTables {
   std::unordered_map<Entry, uint32_t, Entry::Hasher> nz_LUT;
 
   bool initialized;
-
 };
 
 }  // namespace serac
diff --git a/src/serac/numerics/functional/functional.hpp b/src/serac/numerics/functional/functional.hpp
index 50b33bd8ae..9cd91ed7d6 100644
--- a/src/serac/numerics/functional/functional.hpp
+++ b/src/serac/numerics/functional/functional.hpp
@@ -576,7 +576,8 @@ class Functional<test(trials...), exec> {
       constexpr bool col_ind_is_sorted = true;
 
       if (!lookup_tables.initialized) {
-        lookup_tables.init(form_.G_test_[Domain::Type::Elements], form_.G_trial_[Domain::Type::Elements][which_argument]);
+        lookup_tables.init(form_.G_test_[Domain::Type::Elements],
+                           form_.G_trial_[Domain::Type::Elements][which_argument]);
       }
 
       double* values = new double[lookup_tables.nnz]{};

From 97fa3ef71520515dd387bfde8ec52bef43e45fd5 Mon Sep 17 00:00:00 2001
From: Michael Tupek <tupek2@llnl.gov>
Date: Mon, 5 Aug 2024 15:08:08 -0700
Subject: [PATCH 3/3] Fix docs.

---
 src/serac/numerics/functional/dof_numbering.hpp | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/serac/numerics/functional/dof_numbering.hpp b/src/serac/numerics/functional/dof_numbering.hpp
index 39c671f617..0c9bec0412 100644
--- a/src/serac/numerics/functional/dof_numbering.hpp
+++ b/src/serac/numerics/functional/dof_numbering.hpp
@@ -374,6 +374,7 @@ struct GradientAssemblyLookupTables {
    */
   std::unordered_map<Entry, uint32_t, Entry::Hasher> nz_LUT;
 
+  /// @brief specifies if the table has already been initialized or not
   bool initialized;
 };