# Parameter File Example¶

Below we describe the different sections of the “HelloWorld.in” input file we ran in the previous section:

The example input file begins with a comment header. Comments in Cello parameter files begin with # :

### Problem: Hello World
### Summary: Evolve high-pressure region shaped as an "E"
###    Date: 2011-10-27


Parameters are organized into “groups”, which may be nested. Below we look in turn at each group in the HelloWorld.in sample parameter file.

## Domain Group¶

Domain {
lower = [ 0.0, 0.0 ];
upper = [ 1.0, 1.0 ];
}


## Mesh Group¶

Mesh {
root_size      = [160, 160];
root_blocks    = [  1,   1 ];
}


## Field Group¶

Field {

ghost_depth  = 3;
courant = 0.8;

fields = [
"density",
"velocity_x",
"velocity_y",
"total_energy",
"internal_energy"
];
}


## Method Group¶

Method {

sequence = [ "ppm" ];

ppm {
diffusion   = true;
flattening  = 3;
steepening  = true;
dual_energy = false;
}
}


## Physics Group¶

Physics {

dimensions = 2;
gamma = 1.4;

}


## Initial Group¶

Initial {
density       { value = [ 1.0,
(0.35 < x && x < 0.40 && 0.25 < y && y < 0.70) ||
(0.35 < x && x < 0.60 && 0.25 < y && y < 0.30) ||
(0.35 < x && x < 0.60 && 0.45 < y && y < 0.50) ||
(0.35 < x && x < 0.60 && 0.65 < y && y < 0.70),
0.125 ]; };
total_energy  { value = [ 1.0  / (0.4 * 1.0) ,
(0.35 < x && x < 0.40 && 0.25 < y && y < 0.75) ||
(0.35 < x && x < 0.60 && 0.25 < y && y < 0.30) ||
(0.35 < x && x < 0.60 && 0.45 < y && y < 0.55) ||
(0.35 < x && x < 0.60 && 0.65 < y && y < 0.75),
0.14 / (0.4 * 0.1)]; };
velocity_x    { value = [0.0]; };
velocity_y    { value = [0.0]; }
}


## Boundary Group¶

Boundary { type = "reflecting" }


## Stopping Group¶

Stopping {
cycle = 500;
}


## Output Group¶

Output {

file_groups = ["cycle_step"];

cycle_step {
field_list = ["density"];
type     = "image";
name       = ["E-%03d.png","cycle"];
schedule = ["cycle","interval", 10];
colormap_alpha = [0.00, 0.00, 1.00, 0.0,
0.00, 1.00, 0.00, 0.33,
1.00, 1.00, 0.00, 0.66,
1.00, 0.00, 0.00, 1.0];
}
}