From 2e26d47362c9efa819f9221befb54498a5b677d7 Mon Sep 17 00:00:00 2001
From: Grzegorz Kowal <grzegorz@gkowal.info>
Date: Tue, 31 Jul 2012 14:14:42 -0300
Subject: [PATCH] Add two arrays of conserved variables to the block structure.

In these two arrays we store temporary states during the Runge-Kutta
integration.  The new pointer %u in the block structure points to the
current array of the conservative variables.
---
 src/blocks.F90 | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/src/blocks.F90 b/src/blocks.F90
index b0e148a..2b3e4a6 100644
--- a/src/blocks.F90
+++ b/src/blocks.F90
@@ -134,10 +134,14 @@ module blocks
                                  !
     type(block_meta), pointer :: meta
 
-                                 ! an allocatable array to store all conserved
+                                 ! a pointer to the array conserved variables
+                                 !
+    real, dimension(:,:,:,:)  , pointer     :: u
+
+                                 ! an allocatable arrays to store all conserved
                                  ! variables
                                  !
-    real, dimension(:,:,:,:)  , allocatable :: u
+    real, dimension(:,:,:,:)  , allocatable :: u0, u1
 
                                  ! an allocatable array to store all primitive
                                  ! variables
@@ -1040,12 +1044,17 @@ module blocks
 
 ! allocate space for conserved variables
 !
-    allocate(pdata%u(nvars,nx,ny,nz))
+    allocate(pdata%u0(nvars,nx,ny,nz))
+    allocate(pdata%u1(nvars,nx,ny,nz))
 
 ! allocate space for primitive variables
 !
     allocate(pdata%q(nvars,nx,ny,nz))
 
+! initiate the array pointer
+!
+    pdata%u => pdata%u0
+
 ! allocate space for the numerical fluxes
 !
     if (nflux .gt. 0) allocate(pdata%f(ndims,nflux,nx,ny,nz))
@@ -1097,7 +1106,8 @@ module blocks
 
 ! deallocate conservative variables
 !
-      if (allocated(pdata%u)) deallocate(pdata%u)
+      if (allocated(pdata%u0)) deallocate(pdata%u0)
+      if (allocated(pdata%u1)) deallocate(pdata%u1)
 
 ! deallocate primitive variables
 !
@@ -1109,6 +1119,7 @@ module blocks
 
 ! nullify pointers
 !
+      nullify(pdata%u)
       nullify(pdata%next)
       nullify(pdata%prev)
       nullify(pdata%meta)