Fix QED Build (CUDA 10.0) (#1888)

Replace capture of a host-side array with unnamed members for E & B
field transport with a nicely named struct that transports the
Array4's as members.

This is harder to mix up and thus more self-documenting and solves an
issue with NVCC 10.0 of the form:
```
nvcc_internal_extended_lambda_implementation: In instantiation of '__nv_dl_wrapper_t<Tag, F1, F2, F3, F4, F5>::__nv_dl_wrapper_t(F1, F2, F3, F4, F5) [with Tag = __nv_dl_tag<int (*)(amrex::ParticleTile<0, 0, 4, 0, amrex::ArenaAllocator>&, amrex::ParticleTile<0, 0, 4, 0, amrex::ArenaAllocator>&, amrex::Box, const amrex::Array4<const double> (&)[6], int, int, const SchwingerFilterFunc&, const SmartCreate&, const SmartCreate&, const SchwingerTransformFunc&), filterCreateTransformFromFAB<1, amrex::ParticleTile<0, 0, 4, 0, amrex::ArenaAllocator>, amrex::Array4<const double> [6], int, const SchwingerFilterFunc&, const SmartCreate&, const SmartCreate&, const SchwingerTransformFunc&>, 1>; F1 = amrex::Array4<double>; F2 = const SchwingerFilterFunc; F3 = const amrex::Array4<const double> [6]; F4 = const amrex::Box; F5 = int*]':
/home/ubuntu/repos/WarpX/Source/Particles/ParticleCreation/FilterCreateTransformFromFAB.H:174:28:   required from 'Index filterCreateTransformFromFAB(DstTile&, DstTile&, amrex::Box, const FABs&, Index, Index, FilterFunc&&, CreateFunc1&&, CreateFunc2&&, TransFunc&&) [with int N = 1; DstTile = amrex::ParticleTile<0, 0, 4, 0, amrex::ArenaAllocator>; FABs = amrex::Array4<const double> [6]; Index = int; FilterFunc = const SchwingerFilterFunc&; CreateFunc1 = const SmartCreate&; CreateFunc2 = const SmartCreate&; TransFunc = const SchwingerTransformFunc&]'
/home/ubuntu/repos/WarpX/Source/Particles/MultiParticleContainer.cpp:1169:167:   required from here
nvcc_internal_extended_lambda_implementation:70:103: error: invalid initializer for array member 'const amrex::Array4<const double> __nv_dl_wrapper_t<__nv_dl_tag<int (*)(amrex::ParticleTile<0, 0, 4, 0, amrex::ArenaAllocator>&, amrex::ParticleTile<0, 0, 4, 0, amrex::ArenaAllocator>&, amrex::Box, const amrex::Array4<const double> (&)[6], int, int, const SchwingerFilterFunc&, const SmartCreate&, const SmartCreate&, const SchwingerTransformFunc&), filterCreateTransformFromFAB<1, amrex::ParticleTile<0, 0, 4, 0, amrex::ArenaAllocator>, amrex::Array4<const double> [6], int, const SchwingerFilterFunc&, const SmartCreate&, const SmartCreate&, const SchwingerTransformFunc&>, 1>, amrex::Array4<double>, const SchwingerFilterFunc, const amrex::Array4<const double> [6], const amrex::Box, int*>::f3 [6]'
```

1 files changed, 14 insertions, 11 deletions

diff --git a/Source/Particles/MultiParticleContainer.cpp b/Source/Particles/MultiParticleContainer.cpp
index 1b2f920a9..4218e9fdf 100644
--- a/Source/Particles/MultiParticleContainer.cpp
+++ b/Source/Particles/MultiParticleContainer.cpp
@@ -27,6 +27,15 @@
 
 using namespace amrex;
 
+namespace
+{
+    /** A little collection to transport six Array4 that point to the EM fields */
+    struct MyFieldList
+    {
+        Array4< amrex::Real const > const Ex, Ey, Ez, Bx, By, Bz;
+    };
+}
+
 MultiParticleContainer::MultiParticleContainer (AmrCore* amr_core)
 {
 
@@ -1138,15 +1147,9 @@ MultiParticleContainer::doQEDSchwinger ()
         if (!box.intersects(global_schwinger_box)) {continue;}
         box &= global_schwinger_box;
 
-        const auto& arrEx = Ex[mfi].array();
-        const auto& arrEy = Ey[mfi].array();
-        const auto& arrEz = Ez[mfi].array();
-        const auto& arrBx = Bx[mfi].array();
-        const auto& arrBy = By[mfi].array();
-        const auto& arrBz = Bz[mfi].array();
-
-        const Array4<const amrex::Real> array_EMFAB [] = {arrEx,arrEy,arrEz,
-                                           arrBx,arrBy,arrBz};
+        const MyFieldList fieldsEB = {
+            Ex[mfi].array(), Ey[mfi].array(), Ez[mfi].array(),
+            Bx[mfi].array(), By[mfi].array(), Bz[mfi].array()};
 
         auto& dst_ele_tile = pc_product_ele->ParticlesAt(level_0, mfi);
         auto& dst_pos_tile = pc_product_pos->ParticlesAt(level_0, mfi);
@@ -1167,9 +1170,9 @@ MultiParticleContainer::doQEDSchwinger ()
                             ParticleStringNames::to_index.find("w")->second};
 
         const auto num_added = filterCreateTransformFromFAB<1>( dst_ele_tile,
-                              dst_pos_tile, box, array_EMFAB, np_ele_dst,
+                               dst_pos_tile, box, fieldsEB, np_ele_dst,
                                np_pos_dst,Filter, CreateEle, CreatePos,
-                                Transform);
+                               Transform);
 
         setNewParticleIDs(dst_ele_tile, np_ele_dst, num_added);
         setNewParticleIDs(dst_pos_tile, np_pos_dst, num_added);