Allow time integrator initialise with a method name.

src/time_integrator.f90

@@ -61,10 +61,10 @@ function init(backend, allocator, method, nvars)
     type(time_intg_t) :: init
     class(base_backend_t), pointer :: backend
     class(allocator_t), pointer :: allocator
-    integer, intent(in), optional :: method
+    character(3), intent(in), optional :: method
     integer, intent(in), optional :: nvars
 
-    integer :: i, j
+    integer :: i, j, stat
 
     ! initialize Runge-Kutta coefficients
     ! rk1
@@ -110,24 +110,28 @@ function init(backend, allocator, method, nvars)
     init%allocator => allocator
 
     if (present(method)) then
-      init%method = method
+      init%sname = method
     else
-      init%method = 3
+      init%sname = 'AB3'
     end if
-    if (init%method < 5) then
-      ! method 1 to 4 -> AB1 to AB4
-      init%order = init%method
-      init%nstep = init%method
+
+    if (init%sname(1:2) == 'AB') then
+      read (init%sname(3:3), *, iostat=stat) init%order
+      if (stat /= 0) error stop 'Error reading AB integration order'
+      if (init%order >= 5) error stop 'Integration order >4 is not supported'
+      init%nstep = init%order
       init%nstage = 1
       init%nolds = init%nstep - 1
-      write (init%sname, "(A2,I1)") "AB", init%order
-    else
-      ! method 5 to 8 -> RK1 to RK4
-      init%order = init%method - 4
+    else if (init%sname(1:2) == 'RK') then
+      read (init%sname(3:3), *, iostat=stat) init%order
+      if (stat /= 0) error stop 'Error reading RK integration order'
+      if (init%order >= 5) error stop 'Integration order >4 is not supported'
       init%nstep = 1
-      init%nstage = init%method - 4
+      init%nstage = init%order
       init%nolds = init%nstage
-      write (init%sname, "(A2,I1)") "RK", init%order
+    else
+      print *, 'Integration method '//init%sname//' is not defined'
+      error stop
     end if
 
     if (present(nvars)) then
@@ -151,8 +155,6 @@ function init(backend, allocator, method, nvars)
       end do
     end do
 
-    print *, init%sname, ' time integrator instantiated'
-
   end function init
 
   subroutine step(self, u, v, w, du, dv, dw, dt)
@@ -174,7 +176,7 @@ subroutine step(self, u, v, w, du, dv, dw, dt)
     self%deriv(2)%ptr => dv
     self%deriv(3)%ptr => dw
 
-    if (self%method < 5) then
+    if (self%sname(1:2) == 'AB' ) then
       call self%adams_bashforth(dt)
     else
       call self%runge_kutta(dt)

src/xcompact.f90

@@ -103,8 +103,9 @@ program xcompact
   if (nrank == 0) print *, 'OpenMP backend instantiated'
 #endif
 
-  time_integrator = time_intg_t(allocator=allocator, backend=backend)
-  if (nrank == 0) print *, 'time integrator instantiated'
+  time_integrator = time_intg_t(allocator=allocator, backend=backend, &
+                                method='AB3')
+  if (nrank == 0) print *, time_integrator%sname//' time intg instantiated'
   solver = solver_t(backend, mesh, time_integrator, host_allocator)
   if (nrank == 0) print *, 'solver instantiated'
 

tests/test_time_integrator.f90

@@ -21,6 +21,7 @@ program test_omp_adamsbashforth
   logical :: allpass = .true.
   integer :: i, j, k, stage, istartup, nrank, nproc, ierr
   integer :: nstep0 = 64, nstep, nrun = 4, nmethod = 8
+  character(len=3) :: method(8)
   real(dp), allocatable, dimension(:) :: err
   real(dp), allocatable, dimension(:) :: norm
   real(dp) :: dt0 = 0.01_dp, dt, order
@@ -95,12 +96,14 @@ program test_omp_adamsbashforth
 
   allocate (norm(nrun))
 
+  method = ['AB1', 'AB2', 'AB3', 'AB4', 'RK1', 'RK2', 'RK3', 'RK4']
+
   ! compute l2 norm for various step sizes
   do k = 1, nmethod
 
     ! initialize time-integrator
     time_integrator = time_intg_t(allocator=allocator, &
-                                  backend=backend, method=k)
+                                  backend=backend, method=method(k))
 
     dt = dt0
     nstep = nstep0