Running¶
Pyro can be run in two ways: either from the commandline, using the pyro.py
script and passing in the solver, problem and inputs as arguments, or by using
the Pyro
class.
Commandline¶
The pyro.py
script takes 3
arguments: the solver name, the problem setup to run with that solver
(this is defined in the solver’s problems/
sub-directory), and the
inputs file (again, usually from the solver’s problems/
directory).
For example, to run the Sedov problem with the compressible solver we would do:
./pyro.py compressible sedov inputs.sedov
This knows to look for inputs.sedov
in compressible/problems/
(alternately, you can specify the full path for the inputs file).
To run the smooth Gaussian advection problem with the advection solver, we would do:
./pyro.py advection smooth inputs.smooth
Any runtime parameter can also be specified on the command line, after the inputs file. For example, to disable runtime visualization for the above run, we could do:
./pyro.py advection smooth inputs.smooth vis.dovis=0
Note
Quite often, the slowest part of the runtime is the visualization, so disabling
vis as shown above can dramatically speed up the execution. You can always
plot the results after the fact using the plot.py
script, as discussed
in Analysis routines.
Pyro class¶
Alternatively, pyro can be run using the Pyro
class. This provides
an interface that enables simulations to be set up and run in a Jupyter notebook – see
examples/examples.ipynb
for an example notebook. A simulation can be set up and run
by carrying out the following steps:
- create a
Pyro
object, initializing it with a specific solver - initialize the problem, passing in runtime parameters and inputs
- run the simulation
For example, if we wished to use the compressible
solver to run the
Kelvin-Helmholtz problem kh
, we would do the following:
from pyro import Pyro
pyro = Pyro("compressible")
pyro.initialize_problem(problem_name="kh",
inputs_file="inputs.kh")
pyro.run_sim()
Instead of using an inputs file to define the problem parameters, we can define a
dictionary of parameters and pass them into the initialize_problem
function using the keyword argument inputs_dict
.
If an inputs file is also passed into the function, the parameters in the dictionary
will override any parameters in the file. For example, if we wished to turn off
visualization for the previous example, we would do:
parameters = {"vis.dovis":0}
pyro.initialize_problem(problem_name="kh",
inputs_file="inputs.kh",
inputs_dict=parameters)
It’s possible to evolve the simulation forward timestep by timestep manually using
the single_step
function (rather than allowing
run_sim
to do this for us). To evolve our example
simulation forward by a single step, we’d run
pyro.single_step()
This will fill the boundary conditions, compute the timestep dt
, evolve a
single timestep and do output/visualization (if required).
Runtime options¶
The behavior of the main driver, the solver, and the problem setup can
be controlled by runtime parameters specified in the inputs file (or
via the command line or passed into the initialize_problem
function).
Runtime parameters are grouped into sections,
with the heading of that section enclosed in [ .. ]
. The list of
parameters are stored in three places:
- the
pyro/_defaults
file - the solver’s
_defaults
file - problem’s
_defaults
file (named_problem-name.defaults
in the solver’sproblem/
sub-directory).
These three files are parsed at runtime to define the list of valid
parameters. The inputs file is read next and used to override the
default value of any of these previously defined
parameters. Additionally, any parameter can be specified at the end of
the commandline, and these will be used to override the defaults. The
collection of runtime parameters is stored in a
RuntimeParameters
object.
The runparams.py
module in util/
controls access to the runtime
parameters. You can setup the runtime parameters, parse an inputs
file, and access the value of a parameter (hydro.cfl
in this example)
as:
rp = RuntimeParameters()
rp.load_params("inputs.test")
...
cfl = rp.get_param("hydro.cfl")
When pyro is run, the file inputs.auto
is output containing the
full list of runtime parameters, their value for the simulation, and
the comment that was associated with them from the _defaults
files. This is a useful way to see what parameters are in play for a
given simulation.
All solvers use the following parameters:
section: [driver]
option value description tmax 1.0
maximum simulation time to evolve max_steps 10000
maximum number of steps to take fix_dt -1.0
init_tstep_factor 0.01
first timestep = init_tstep_factor * CFL timestep max_dt_change 2.0
max amount the timestep can change between steps verbose 1.0
verbosity section: [io]
option value description basename pyro_
basename for output files dt_out 0.1
simulation time between writing output files n_out 10000
number of timesteps between writing output files do_io 1
do we output at all? section: [mesh]
option value description xmin 0.0
domain minumum x-coordinate xmax 1.0
domain maximum x-coordinate ymin 0.0
domain minimum y-coordinate ymax 1.0
domain maximum y-coordinate xlboundary reflect
minimum x BC (‘reflect’, ‘outflow’, or ‘periodic’) xrboundary reflect
maximum x BC (‘reflect’, ‘outflow’, or ‘periodic’) ylboundary reflect
minimum y BC (‘reflect’, ‘outflow’, or ‘periodic’) yrboundary reflect
maximum y BC (‘reflect’, ‘outflow’, or ‘periodic’) nx 25
number of zones in the x-direction ny 25
number of zones in the y-direction section: [particles]
option value description do_particles 0
include particles? (1=yes, 0=no) n_particles 100
number of particles particle_generator random
how do we generate particles? (random, grid) section: [vis]
option value description dovis 1
runtime visualization? (1=yes, 0=no) store_images 0
store vis images to files (1=yes, 0=no)