New module for interpolation.

This new module contains subroutines used to different kind of
interpolation. So far it is implemented only one subroutine used for
reconstruction of the left and right states from center values. This
interpolation has TVD property.

src/interpolation.F90

@@ -0,0 +1,93 @@
+!!*****************************************************************************
+!!
+!! module: interpolation - subroutines for different kinds of interpolation
+!!
+!! Copyright (C) 2008 Grzegorz Kowal <kowal@astro.wisc.edu>
+!!
+!!*****************************************************************************
+!!
+!!  This file is part of Godunov-AMR.
+!!
+!!  Godunov-AMR is free software; you can redistribute it and/or modify
+!!  it under the terms of the GNU General Public License as published by
+!!  the Free Software Foundation; either version 3 of the License, or
+!!  (at your option) any later version.
+!!
+!!  Godunov-AMR is distributed in the hope that it will be useful,
+!!  but WITHOUT ANY WARRANTY; without even the implied warranty of
+!!  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+!!  GNU General Public License for more details.
+!!
+!!  You should have received a copy of the GNU General Public License
+!!  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+!!
+!!*****************************************************************************
+!!
+!
+module interpolation
+
+  implicit none
+
+  contains
+!
+!===============================================================================
+!
+! reconstruct: subroutine for the reconstruction of the values at the right and
+!              left interfaces of cells from their cell centered representation
+!
+!===============================================================================
+!
+  subroutine reconstruct(n, vx, vl, vr)
+
+    implicit none
+
+! input/output arguments
+!
+    integer           , intent(in)  :: n
+    real, dimension(n), intent(in)  :: vx
+    real, dimension(n), intent(out) :: vl, vr
+
+! local variables
+!
+    integer            :: i
+    real               :: dv
+    real, dimension(n) :: ds, dvl, dvr
+!
+!------------------------------------------------------------------------------
+!
+! second order interpolation
+!
+    dvl(1) = 0.0
+    dvr(n) = 0.0
+
+    do i = 1, n-1
+      dvr(i  ) = vx(i+1) - vx(i)
+      dvl(i+1) = dvr(i)
+    enddo
+
+    do i = 1, n
+      ds (i) = dvr(i) * dvl(i)
+
+      if (ds(i) .gt. 0.0) then
+        dv  = ds(i) / (dvr(i) + dvl(i))
+
+        vl(i) = vx(i) + dv
+        vr(i) = vx(i) - dv
+      else
+        vl(i) = vx(i)
+        vr(i) = vx(i)
+      endif
+    enddo
+
+    do i = 1, n-1
+      vr(i) = vr(i+1)
+    enddo
+    vr(n) = vx(n)
+
+!-------------------------------------------------------------------------------
+!
+  end subroutine reconstruct
+
+!===============================================================================
+!
+end module

src/makefile

@@ -78,10 +78,10 @@ name = godunov-amr
 
 default: $(name).x
 
-sources = blocks.F90 config.F90 driver.F90 error.F90 evolution.F90 io.F90 \
+sources = blocks.F90 config.F90 driver.F90 error.F90 evolution.F90             \
-          mesh.F90 problem.F90 scheme.F90 timer.F90
+          interpolation.F90 io.F90 mesh.F90 problem.F90 scheme.F90 timer.F90
-objects = blocks.o   config.o   driver.o   error.o   evolution.o   io.o   \
+objects = blocks.o   config.o   driver.o   error.o   evolution.o               \
-          mesh.o   problem.o   scheme.o   timer.o
+          interpolation.o   io.o   mesh.o   problem.o   scheme.o   timer.o
 files   = $(sources) makefile make.default config.in license.txt hosts
 
 $(name).x: $(objects)
@@ -103,10 +103,11 @@ config.o        : config.F90 error.o
 driver.o        : driver.F90 config.o evolution.o io.o mesh.o timer.o
 error.o         : error.F90
 evolution.o     : evolution.F90 blocks.o config.o mesh.o scheme.o
+interpolation.o : interpolation.F90
 io.o            : io.F90 blocks.o error.o
 mesh.o          : mesh.F90 blocks.o config.o error.o problem.o
 problem.o       : problem.F90 blocks.o
-scheme.o        : scheme.F90 blocks.o config.o
+scheme.o        : scheme.F90 blocks.o config.o interpolation.o
 timer.o         : timer.F90
 
 #-------------------------------------------------------------------------------

src/scheme.F90

@@ -188,7 +188,7 @@ module scheme
 !
   subroutine hll(m, n, uc, f)
 
-!     use interpolation, only : reconstruct, point2avg
+    use interpolation, only : reconstruct
 
     implicit none
 
@@ -205,8 +205,6 @@ module scheme
     real, dimension(m,n) :: fl, fr, fx
     real, dimension(n)   :: cl, cr
     real                 :: al, ar, ap, div
-
-    integer, parameter, dimension(6)    :: pos = (/ 1, 0, 0, 0, 1, 1 /)
 !
 !----------------------------------------------------------------------
 !
@@ -214,7 +212,7 @@ module scheme
 ! reconstruct left and right states of conserved variables
 !
     do p = 1, m
-!       call reconstruct(n,uc(p,:),ul(p,:),ur(p,:),pos(p))
+      call reconstruct(n,uc(p,:),ul(p,:),ur(p,:))
     enddo
 
 ! calculate primitive variables
@@ -230,7 +228,7 @@ module scheme
 ! reconstruct left and right states of primitive variables
 !
     do p = 1, m
-!       call reconstruct(n,qc(p,:),ql(p,:),qr(p,:),pos(p))
+      call reconstruct(n,qc(p,:),ql(p,:),qr(p,:))
     enddo
 
 ! calculate conservative variables at states