1.2 Compiling the code

You need to go first to the bin/directory:

$ cd trunk/ramses/bin
$ ls -F
Makefile    Makefile.rt

We will use the first Makefile to compile the code. The first thing to do is to edit the Makefile and modify the two variables F90 and FFLAGS. Several examples corresponding to different Fortran compilers are given. The default values are:

F90 = gfortran -O3 -frecord-marker=4 -fbacktrace -ffree-line-length-none
FFLAGS = -x f95-cpp-input -DWITHOUTMPI $(DEFINES)

The first variable is obviously the command used to invoke the Fortran compiler. In this case, this is the GNU Fortran compiler. The second variable contains Fortran compilation flags and preprocessor directives. The first directive, -DWITHOUTMPI, switches off all MPI routines. On the other hand, if you don't use this directive, the code must be linked to the MPI library. We will discuss this point later.

Other preprocessor directives are defined in variable DEFINES in the Makefile:

# Compilation time parameters
NVECTOR = 64
NDIM = 3
NPRE = 8
NVAR = 8
SOLVER = hydro
PATCH =
EXEC = ramses
DEFINES = -DNVECTOR=$(NVECTOR) -DNDIM=$(NDIM) -DNPRE=$(NPRE) -DNVAR=$(NVAR) -DSOLVER$(SOLVER)

These additional directives are called Compilation Time Parameters. They should be defined in the Makefile and the code must be recompiled entirely using:

$ make clean
$ make

We list now the definitions of these parameters.

NVECTOR=64

This parameter is used to set the vector size for computation-intensive operations. It must be determined experimentally on each new hardware.

NPRE=4

This parameter sets the precision of the floating point operations. NPRE=4stands for single precision arithmetics, while NPRE=8 is for double precision.

NENER=0

This parameter sets the number of energy variables used in the hydro or mhd solver.

NDIM=3

This parameter sets the dimensionality of the problem. The value NDIM=1is for 1D, plan-parallel flows. NDIM=2 and NDIM=3 are resp. for 2D and 3D flows.

SOLVER=hydro

This parameter selects the type of hyperbolic solver used. Possible values are: hydro for the adiabatic Euler equations, mhd, the Constrained Transport scheme for the ideal MHD equations. and rhd for relativistic hydro.

NVAR=8

This parameters defines the number of variables in the hyperbolic solver. For SOLVER=hydro, NVAR>=NDIM+2. For SOLVER=mhd, NVAR>=8 and for SOLVER=rhd, one has NVAR>=5.

Our goal is now to compile the code for a simple one-dimensional problem. You need to modify the Makefile so that:

NDIM=1
SOLVER=hydro
NVAR=3

Then type:

$ make

If everything goes well, all source files will be compiled and linked into an executable called ramses1d.

1.2.1 Additional compilation preprocessor flags

-DTSC

This parameter sets the triangular shape cloud approximation; only works with NDIM=3

-DOUTPUT_PARTICLE_POTENTIAL

This parameter forces the code to output particle potentials at snapshots

-DQUADHILBERT

This parameter sets longer Hilbert curve necessary if levelmax>19

-DLONGINT

This parameter switches to long ints (necessary when one has lots of particles)

-DNOSYSTEM

This parameter handles operating system commands

Next step: executing the test case !