Allow setting iout?d to 0 for no output. (#128)

* set iout?d,isave,icheck to 0 for no operations

* Minor edits by Pedro.

* Updated the docs.

---------

Co-authored-by: Pedro Costa <p.simoes.costa@gmail.com>

docs/INFO_INPUT.md

@@ -157,7 +157,7 @@ These lines set the frequency of time step checking and output:
 * every `iout3d` time steps **3d scalar fields** are written to a file
 * every `isave`  time steps a **checkpoint file** is written (`fld_???????.bin`), and a symbolic link for the restart file, `fld.bin`, will point to this last save so that, by default, the last saved checkpoint file is used to restart the simulation
 
-1d, 2d and 3d outputs can be tweaked modifying files `out?d.h90`, and re-compiling the source. See also `output.f90` for more details.
+1d, 2d and 3d outputs can be tweaked modifying files `out?d.h90`, and re-compiling the source. See also `output.f90` for more details. _Set any of these variables to `0` to skip the corresponding operation._
 
 ---
 

src/main.f90

@@ -325,9 +325,15 @@ program cans
   write(fldnum,'(i7.7)') istep
   !$acc wait ! not needed but to prevent possible future issues
   !$acc update self(u,v,w,p)
-  include 'out1d.h90'
-  include 'out2d.h90'
-  include 'out3d.h90'
+  if(iout1d > 0.and.mod(istep,max(iout1d,1)) == 0) then
+    include 'out1d.h90'
+  end if
+  if(iout2d > 0.and.mod(istep,max(iout2d,1)) == 0) then
+    include 'out2d.h90'
+  end if
+  if(iout3d > 0.and.mod(istep,max(iout3d,1)) == 0) then
+    include 'out3d.h90'
+  end if
   !
   call chkdt(n,dl,dzci,dzfi,visc,u,v,w,dtmax)
   dt = min(cfl*dtmax,dtmin)
@@ -460,7 +466,7 @@ program cans
       tw = (MPI_WTIME()-twi)/3600.
       if(tw    >= tw_max  ) is_done = is_done.or..true.
     end if
-    if(mod(istep,icheck) == 0) then
+    if(icheck > 0.and.mod(istep,max(icheck,1)) == 0) then
       if(myid == 0) print*, 'Checking stability and divergence...'
       call chkdt(n,dl,dzci,dzfi,visc,u,v,w,dtmax)
       dt  = min(cfl*dtmax,dtmin)
@@ -486,7 +492,7 @@ program cans
     !
     ! output routines below
     !
-    if(mod(istep,iout0d) == 0) then
+    if(iout0d > 0.and.mod(istep,max(iout0d,1)) == 0) then
       !allocate(var(4))
       var(1) = 1.*istep
       var(2) = dt
@@ -514,22 +520,22 @@ program cans
       end if
     end if
     write(fldnum,'(i7.7)') istep
-    if(mod(istep,iout1d) == 0) then
+    if(iout1d > 0.and.mod(istep,max(iout1d,1)) == 0) then
       !$acc wait
       !$acc update self(u,v,w,p)
       include 'out1d.h90'
     end if
-    if(mod(istep,iout2d) == 0) then
+    if(iout2d > 0.and.mod(istep,max(iout2d,1)) == 0) then
       !$acc wait
       !$acc update self(u,v,w,p)
       include 'out2d.h90'
     end if
-    if(mod(istep,iout3d) == 0) then
+    if(iout3d > 0.and.mod(istep,max(iout3d,1)) == 0) then
       !$acc wait
       !$acc update self(u,v,w,p)
       include 'out3d.h90'
     end if
-    if(mod(istep,isave ) == 0.or.(is_done.and..not.kill)) then
+    if(isave > 0.and.((mod(istep,max(isave,1)) == 0).or.(is_done.and..not.kill))) then
       if(is_overwrite_save) then
         filename = 'fld.bin'
       else