From ba6cd074c546c26855bcf4e7acfd69046586e51c Mon Sep 17 00:00:00 2001
From: Wolfgang Bangerth <bangerth@math.tamu.edu>
Date: Tue, 13 Oct 2015 15:11:39 -0500
Subject: [PATCH] Omit PETSc/Trilinos wrappers when building without these
 libraries.

When building without PETSc, Trilinos, or SLEPc, the files we compile are empty.
There is no point doing so, so exclude them from compilation if they are not
needed.
---
 source/lac/CMakeLists.txt | 84 ++++++++++++++++++++++++++-------------
 1 file changed, 56 insertions(+), 28 deletions(-)

diff --git a/source/lac/CMakeLists.txt b/source/lac/CMakeLists.txt
index 6b06ee08cd..b4de9e64e3 100644
--- a/source/lac/CMakeLists.txt
+++ b/source/lac/CMakeLists.txt
@@ -30,25 +30,10 @@ SET(_src
   matrix_lib.cc
   matrix_out.cc
   parallel_vector.cc
-  petsc_block_sparse_matrix.cc
-  petsc_full_matrix.cc
-  petsc_matrix_base.cc
-  petsc_matrix_free.cc
-  petsc_parallel_block_sparse_matrix.cc
-  petsc_parallel_block_vector.cc
-  petsc_parallel_sparse_matrix.cc
-  petsc_parallel_vector.cc
-  petsc_precondition.cc
-  petsc_solver.cc
-  petsc_sparse_matrix.cc
-  petsc_vector_base.cc
-  petsc_vector.cc
   precondition_block.cc
   precondition_block_ez.cc
   relaxation_block.cc
   read_write_vector.cc
-  slepc_solver.cc
-  slepc_spectral_transformation.cc
   solver.cc
   solver_control.cc
   sparse_decomposition.cc
@@ -63,17 +48,6 @@ SET(_src
   sparsity_tools.cc
   swappable_vector.cc
   tridiagonal_matrix.cc
-  trilinos_block_sparse_matrix.cc
-  trilinos_block_vector.cc
-  trilinos_parallel_block_vector.cc
-  trilinos_precondition.cc
-  trilinos_precondition_ml.cc
-  trilinos_precondition_muelu.cc
-  trilinos_solver.cc
-  trilinos_sparse_matrix.cc
-  trilinos_sparsity_pattern.cc
-  trilinos_vector_base.cc
-  trilinos_vector.cc
   vector.cc
   vector_memory.cc
   vector_view.cc
@@ -93,13 +67,67 @@ SET(_inst
   solver.inst.in
   sparse_matrix_ez.inst.in
   sparse_matrix.inst.in
-  trilinos_sparse_matrix.inst.in
-  trilinos_vector_base.inst.in
   vector.inst.in
   vector_memory.inst.in
   vector_view.inst.in
   )
 
+# Add PETSc wrapper files. If PETSc has not been found,
+# then these files should be empty and there is no need
+# to even look at them
+IF(DEAL_II_WITH_PETSC)
+  SET(_src
+    ${_src}
+    petsc_block_sparse_matrix.cc
+    petsc_full_matrix.cc
+    petsc_matrix_base.cc
+    petsc_matrix_free.cc
+    petsc_parallel_block_sparse_matrix.cc
+    petsc_parallel_block_vector.cc
+    petsc_parallel_sparse_matrix.cc
+    petsc_parallel_vector.cc
+    petsc_precondition.cc
+    petsc_solver.cc
+    petsc_sparse_matrix.cc
+    petsc_vector_base.cc
+    petsc_vector.cc
+  )
+ENDIF()
+
+# Same for SLEPc
+IF(DEAL_II_WITH_SLEPC)
+  SET(_src
+    ${_src}
+    slepc_solver.cc
+    slepc_spectral_transformation.cc
+  )
+ENDIF()
+
+# Also add Trilinos wrapper files
+IF(DEAL_II_WITH_TRILINOS)
+  SET(_src
+    ${_src}
+    trilinos_block_sparse_matrix.cc
+    trilinos_block_vector.cc
+    trilinos_parallel_block_vector.cc
+    trilinos_precondition.cc
+    trilinos_precondition_ml.cc
+    trilinos_precondition_muelu.cc
+    trilinos_solver.cc
+    trilinos_sparse_matrix.cc
+    trilinos_sparsity_pattern.cc
+    trilinos_vector_base.cc
+    trilinos_vector.cc
+  )
+  SET(_inst
+    ${_inst}
+    trilinos_sparse_matrix.inst.in
+    trilinos_vector_base.inst.in
+  )
+ENDIF()
+
+
+
 FILE(GLOB _header
   ${CMAKE_SOURCE_DIR}/include/deal.II/lac/*.h
   )
-- 
2.39.5