7. visit_utils

visit_utils is a pure python module distributed along with Visit’s Python interface. It provides a simple interface to encode movie files and methods that wrap more complex VisIt Python command sequences to simplify a few common use cases. It also provides a stand alone PySide based annotation rendering API.

Here we provide details on the encoding and engine launching modules:

7.1. visit_utils.encoding

visit_utils.encoding provides methods that allow you to use movie encoders (e.g ffmpeg) to encode movies from sequences of image files and extract image files from movie files.

Methods:

visit_utils.encoding.encode(ipattern, ofile, fdup=None, etype=None, stereo=False, input_frame_rate=None, output_frame_rate=None)

Encodes a sequence of images into a movie.

Example Usage:

from visit_utils.encoding import *
encode("input.%04d.png","output.mpg")
encode("input.%04d.png","output.wmv",fdup=5)
encode("input.%04d.png","output.sm")
encode("input.%04d.png","output.sm",stereo=True)
Parameters:

  • ipattern – Input file pattern. Requires a printf-style # format like “file%04d.png”.

  • ofile – Output file name

  • fdup – Allows you to set an integer number of times to duplicate the input frames as they are passed to the encoder. (The duplication actually happens via symlinks) [Default = None]

  • etype – Allows to select which encoder to use ( If not passed the file extension is used to select an encoder ) [Default = None]

  • input_frame_rate – Allows you to set the input frame rate, in frames per second, that the encoder uses. [Default = None]

  • output_frame_rate – Allows you to set the output frame rate, in frames per second, that the encoder uses. Note output formats typically only support a few output fps values. To obtain a perceived fps, the input_frame_rate is a better option to try. [Default = None]

visit_utils.encoding.extract(ifile, opattern)

Extracts a sequence of images from a a movie.

Example:

extract("movie.mpg","output%04d.png")
Parameters:

  • ifile – Input file.

  • opattern – Output file pattern. Requires a printf-style # format like “file%04d.png”.

visit_utils.encoding.encoders()
Returns:

A list of strings of the available encoders.

7.2. visit_utils.engine

visit_utils.engine provides an interface to launch VisIt engines that uses installed host profiles.

Methods:

visit_utils.engine.open(nprocs, method, ppn=1, part=None, bank=None, rtime=None, vdir=None)

Launch VisIt compute engine on the current host.

Example usage:

Launch engine with 36 MPI tasks using default options for this host:

engine.open(nprocs=36)

Launch engine with 36 MPI tasks using a specific partition:

engine.open(nprocs=36, part="pbatch")

Launch engine with 36 MPI tasks, ask for 60 minute time limit:

engine.open(nprocs=36, rtime=60)

If you already have a slurm batch allocation, you can use:

engine.open(method="slurm")

This reads the SLURM_JOB_NUM_NODES and SLURM_CPUS_ON_NODE env vars and uses these values to launch with srun.

If you already have a lsf batch allocation, you can use:

engine.open(method="lsf")

This reads the LSB_DJOB_NUMPROC env var and uses it the to launch with mpirun.

Parameters:

  • nprocs – Number of MPI tasks

  • methods – Launch Method (srun, etc)

  • ppn – MPI tasks per node

  • part – Partition

  • rtime – Job time

  • vdir – Path to VisIt install

visit_utils.engine.close(ename=None)

Closes VisIt’s Compute Engine.

Parameters:

ename – Engine name to close (optional)

visit_utils.engine.supported_hosts()
Returns:

A list of the names of supported hosts.