In situ Visualization with Ascent

Ascent is a system designed to meet the in-situ visualization and analysis needs of simulation code teams running multi-physics calculations on many-core HPC architectures. It provides rendering runtimes that can leverage many-core CPUs and GPUs to render images of simulation meshes.

Compiling with GNU Make

After building and installing Ascent according to the instructions at Building Ascent, you can enable it in WarpX by changing the line

USE_ASCENT_INSITU = FALSE

in GNUmakefile to

USE_ASCENT_INSITU = TRUE

Furthermore, you must ensure that either the ASCENT_HOME shell environment variable contains the directory where Ascent is installed or you must specify this location when invoking make, i.e.,

make -j 8 ASCENT_HOME = /path/to/ascent/install

ParmParse Configuration

Once an AMReX code has been compiled with Ascent enabled, it will need to be enabled and configured at runtime. This is done using ParmParse input file. The supported parameters are described in the following table.

parameter	description	default
insitu.int	turns in situ processing on or off and controls how often data is processed.	0
insitu.start	controls when in situ processing starts.	0

A typical use case is setting insitu.int to a value of one or greater and insitu.start to the first time step where in situ analyswhere in situ analysis should be performed.

Visualization/Analysis Pipeline Configuration

Ascent uses the file ascent_actions.json to configure analysis and visualization pipelines. For example, the following ascent_actions.json file extracts an isosurface of the field Ex for 15 levels and saves the resulting images to levels_<nnnn>.png. Ascent Actions provides an overview over all available analysis and visualization actions.

[
  {
    "action": "add_pipelines",
    "pipelines":
    {
      "p1":
      {
        "f1":
        {
          "type" : "contour",
          "params" :
          {
            "field" : "Ex",
            "levels": 15
          }
        }
      }
    }
  },
  {
    "action": "add_scenes",
    "scenes":
    {
      "s1":
      {
        "image_prefix": "levels_%04d",
        "plots":
        {
        "p1":
          {
            "type": "pseudocolor",
            "pipeline": "p1",
            "field": "Ex"
          }
        }
      }
    }
  },

  {
    "action": "execute"
  },

  {
    "action": "reset"
  }
]