4.2. Dynamics and Infrastructure Implementation¶
The CICE cicecore/ directory consists of the non icepack source code. Within that directory there are the following subdirectories
cicecore/cicedynB/analysis contains higher level history and diagnostic routines.
cicecore/cicedynB/dynamics contains all the dynamical evp, eap, and transport routines.
cicecore/cicedynB/general contains routines associated with forcing, flux calculation, initialization, and model timestepping.
cicecore/cicedynB/infrastructure contains most of the low-level infrastructure associated with communication (halo updates, gather, scatter, global sums, etc) and I/O reading and writing binary and netcdf files.
cicecore/drivers/ contains subdirectories that support stand-alone drivers and other high level coupling layers.
cicecore/shared/ contains some basic methods related to grid decomposition, time managers, constants, kinds, and restart capabilities.
4.2.1. Dynamics¶
4.2.1.1. Dyanamical Solvers¶
The dynamics solvers are found in cicecore/cicedynB/dynamics/. A couple of different solvers are
available including EVP, revised EVP, and EAP. The dynamics solver is specified in namelist with the
kdyn variable. kdyn=1 is evp, kdyn=2 is eap, and revised evp requires the revised_evp
namelist flag be set to true.
4.2.1.2. Transport¶
The transport (advection) methods are found in cicecore/cicedynB/dynamics/. Two methods are supported, upwind and remap. These are set in namelist via the advection variable.
4.2.2. Infrastructure¶
4.2.2.1. Kinds¶
cicecore/shared/ice_kinds_mod.F90 defines the kinds datatypes used in CICE. These kinds are used throughout CICE code to define variable types. The CICE kinds are adopted from the kinds defined in Icepack for consistency in interfaces.
4.2.2.2. Constants¶
cicecore/shared/ice_constants.F90 defines several model constants. Some are hardwired parameters while others have internal defaults and can be set thru namelist.
4.2.2.3. Static Array Allocation¶
CICE is implemented using mainly static arrays. CICE arrays tend to be defined based on the block size and tracer count. Those block sizes and tracer counts are defined in the case cice.settings file, are passed to the build script as CPPs, like
ftn -c … -DNXGLOB=100 -DNYGLOB=116 -DBLCKX=25 -DBLCKY=29 -DMXBLCKS=4 -DNICELYR=7 -DNSNWLYR=1 -DNICECAT=5 -DTRAGE=1 -DTRFY=1 -DTRLVL=1 -DTRPND=1 -DTRBRI=0 -DNTRAERO=1 -DTRZS=0 -DNBGCLYR=7 -DTRALG=0 -DTRBGCZ=0 -DTRDOC=0 -DTRDOC=0 -DTRDIC=0 -DTRDON=0 -DTRFED=0 -DTRFEP=0 -DTRZAERO=0 -DTRBGCS=0 -DNUMIN=11 -DNUMAX=99 …
and then those CPPs replace variable strings in the file cicecore/shared/ice_domain_size.F90. Data in ice_domain_size.F90 provides parameters for static array allocations throughout CICE.
4.2.2.4. Time Manager¶
Time manager data is module data in cicecore/shared/ice_calendar.F90. Much of the time manager data is public and operated on during the model timestepping. The model timestepping actually takes place in the CICE_RunMod.F90 file which is part of the driver code and tends to look like this:
call ice_step
istep = istep + 1 ! update time step counters
istep1 = istep1 + 1
time = time + dt ! determine the time and date
4.2.2.5. Communication¶
Two low-level communications packages, mpi and serial, are provided as part of CICE. This software provides a middle layer between the model and the underlying libraries. Only the CICE mpi or serial directories are compiled with CICE, not both.
cicedynB/infrastructure/comm/mpi/ is based on MPI and provides various methods to do halo updates, global sums, gather/scatter, broadcasts and similar using some fairly generic interfaces to isolate the MPI calls in the code.
cicedynB/infrastructure/comm/serial/ support the same interfaces, but operates in shared memory mode with no MPI. The serial library will be used, by default in the CICE scripts, if the number of MPI tasks is set to 1. The serial library allows the model to be run on a single core or with OpenMP parallelism only without requiring an MPI library.
4.2.2.6. I/O¶
There are three low-level IO packages in CICE, io_netcdf, io_binary, and io_pio. This software
provides a middle layer between the model and the underlying IO writing.
Only one of the three IO directories can be built with CICE. The CICE scripts will build with the io_netcdf
by default, but other options can be selecting by setting ICE_IOTYPE in cice.settings in the
case. This has to be set before CICE is built.
cicedynB/infrastructure/io/io_netcdf/ is the default for the standalone CICE model, and it supports writing history and restart files in netcdf format using standard netcdf calls. It does this by writing from and reading to the root task and gathering and scattering fields from the root task to support model parallelism.
cicedynB/infrastructure/io/io_binary/ supports files in binary format using a gather/scatter approach and reading to and writing from the root task.
cicedynB/infrastructure/io/io_pio/ support reading and writing through the pio interface. pio is a parallel io library (https://github.com/NCAR/ParallelIO) that supports reading and writing of binary and netcdf file through various interfaces including netcdf and pnetcdf. pio is generally more parallel in memory even when using serial netcdf than the standard gather/scatter methods, and it provides parallel read/write capabilities by optionally linking and using pnetcdf.