Allow amgcl without CUDA

opm/simulators/linalg/bda/amgclSolverBackend.cpp

@@ -90,10 +90,14 @@ void amgclSolverBackend<block_size>::initialize(int N_, int nnz_, int dim, doubl
     prm.erase("backend_type_cuda");             // delete custom parameter, otherwise amgcl prints a warning
 
     if (backend_type_cuda) {
+#if HAVE_CUDA
         cudaDeviceProp prop;
         cudaGetDeviceProperties(&prop, deviceID);
         out << prop.name << std::endl;
         cusparseCreate(&CUDA_bprm.cusparse_handle);
+#else
+        OPM_THROW(std::logic_error, "Error amgcl is trying to use CUDA, but CUDA was not found by CMake");
+#endif
     }
     OpmLog::info(out.str());
 
@@ -165,6 +169,7 @@ void amgclSolverBackend<block_size>::solve_system(double *b, WellContributions &
 
     try {
         if (backend_type_cuda) { // use CUDA
+#if HAVE_CUDA
             // create matrix object
             auto A = std::tie(N, A_rows, A_cols, A_vals);
 
@@ -186,6 +191,7 @@ void amgclSolverBackend<block_size>::solve_system(double *b, WellContributions &
             std::tie(iters, error) = solve(B, X);
 
             thrust::copy(X.begin(), X.end(), x.begin());
+#endif
         } else { // use builtin backend (CPU)
             // create matrix object
             auto Atmp = std::tie(N, A_rows, A_cols, A_vals);

opm/simulators/linalg/bda/amgclSolverBackend.hpp

@@ -64,12 +64,15 @@ class amgclSolverBackend : public BdaSolver<block_size>
     using Base::tolerance;
     using Base::initialized;
 
+#if HAVE_CUDA
     typedef amgcl::backend::cuda<double> CUDA_Backend;
+    typedef amgcl::make_solver<amgcl::runtime::preconditioner<CUDA_Backend>, amgcl::runtime::solver::wrapper<CUDA_Backend> > CUDA_Solver;
+#endif
+
     typedef amgcl::static_matrix<double, block_size, block_size> dmat_type; // matrix value type in double precision
     typedef amgcl::static_matrix<double, block_size, 1> dvec_type; // the corresponding vector value type
     typedef amgcl::backend::builtin<dmat_type> CPU_Backend;
 
-    typedef amgcl::make_solver<amgcl::runtime::preconditioner<CUDA_Backend>, amgcl::runtime::solver::wrapper<CUDA_Backend> > CUDA_Solver;
     typedef amgcl::make_solver<amgcl::runtime::preconditioner<CPU_Backend>, amgcl::runtime::solver::wrapper<CPU_Backend> > CPU_Solver;
 
 private:
@@ -82,7 +85,9 @@ private:
                                      // if more backend are supported (vexcl), turn into enum
 
     boost::property_tree::ptree prm;         // amgcl parameters
+#if HAVE_CUDA
     typename CUDA_Backend::params CUDA_bprm; // amgcl backend parameters, only used for cusparseHandle
+#endif
 
     /// Initialize GPU and allocate memory
     /// \param[in] N              number of nonzeroes, divide by dim*dim to get number of blocks