18.2. Advanced Usage¶

build_visit comes with many options for features such as building a parallel version, overcoming issues with OpenGL, a rendering library used by VisIt to render images, and controlling precisely what libraries VisIt is built with.

18.2.1. Building a parallel version¶

One of powerful capabilities of VisIt is running in parallel on large parallel clusters. VisIt runs in parallel using a library called MPI, which stands for Message Passing Interface. There are a couple of ways in which you can build a parallel version of VisIt using MPI. If your system doesn’t already have MPI installed on it, which is typically the case with a desktop system or small cluster, then you can use MPICH, which is an open source implementation of MPI. The following example builds a parallel version using MPICH.

./build_visit3_0_0b --mpich

If your system already has MPI installed on it, which is typically the case with a large system at a computer center, you can set several environment variables that specify the location of the MPI libraries and header files. The following example uses a system installed MPI library.

 env PAR_COMPILER=/usr/packages/mvapich2/bin/mpicc \
     PAR_COMPILER_CXX=/usr/packages/mvapich2/bin/mpicxx \
     PAR_INCLUDE=-I/usr/packages/mvapich2/include \
     PAR_LIBS=-lmpl \
./build_visit3_0_0b --parallel

When running in parallel, the user will typically use scalable rendering for rendering images in parallel. VisIt does this through the use of the Mesa 3D graphics library. Because of this you will want to include Mesa 3D when building a parallel version. In the following example we have included building with the Mesa 3D library.

./build_visit3_0_0b --mpich --osmesa

18.2.2. Building with Mesa as the OpenGL implementation¶

Mesa 3D is also an implementation of OpenGL and it can be used in place of the system OpenGL when building VisIt. There are a couple of reasons you would want to use Mesa 3D instead of the system OpenGL. The first is when you don’t have a system OpenGL, which typically occurs when building in a container or on a virtual machine. The second is when your system implementation of OpenGL is too old to support VTK. In the following example we use Mesa 3D instead of the system OpenGL.

./build_visit3_0_0b --mesagl

18.2.3. The difference between `--mesagl` and `--osmesa`¶

When you specify --mesagl VTK will be built against Mesa 3D. When you specify --osmesa VTK is built against the system OpenGL and the Mesa 3D library is substituted at run time for OpenGL when running the parallel engine to enable scalable rendering. If you specify --mesagl then --osmesa is unnecessary and ignored if specified.

18.2.4. Building on a system without internet access¶

When you want to build visit on a system without internet access, you can use build_visit to download the third party libraries and source code to a system that has internet access and then move those files to your machine without access. The following example downloads the optional libraries, mpich and osmesa.

./build_visit3_0_0b --optional --mpich --osmesa --download-only

Unfortunately, due to the way the code that builds Python is implemented, some Python libraries will not be downloaded. Here is the list of commands to download those additional libraries.

wget http://portal.nersc.gov/project/visit/releases/3.0.0b/third_party/Imaging-1.1.7.tar.gz
wget http://portal.nersc.gov/project/visit/releases/3.0.0b/third_party/setuptools-28.0.0.tar.gz
wget http://portal.nersc.gov/project/visit/releases/3.0.0b/third_party/Cython-0.25.2.tar.gz
wget http://portal.nersc.gov/project/visit/releases/3.0.0b/third_party/numpy-1.14.1.zip
wget http://portal.nersc.gov/project/visit/releases/3.0.0b/third_party/pyparsing-1.5.2.tar.gz
wget http://portal.nersc.gov/project/visit/releases/3.0.0b/third_party/requests-2.5.1.tar.gz
wget http://portal.nersc.gov/project/visit/releases/3.0.0b/third_party/seedme-python-client-v1.2.4.zip

It’s possible that the list could change and the above list becomes outdated. In this case you can run build_visit to just build Python and that will end up downloading all the files you need. The following command builds only Python.

./build_visit3_0_0b --no-thirdparty --no-visit --python

18.2.5. Different versions of `build_visit`¶

When you use a version of build_visit that has a version number in it, for example build_visit3_0_0b then it builds that tagged version of VisIt. If the version of build_visit was from the develop branch of VisIt, then it will grab the latest version of VisIt from the devlop branch. If the version of build_visit came from a release candidate branch, for example the v3.0 branch, then it will grab the latest version of VisIt from that branch.

18.2.6. Troubleshooting `build_visit` failures¶

When build_visit runs, it generates a log file with _log added to the name of the script. For example, if you are running build_visit3_0_0b then the log file will be named build_visit3_0_0b_log. The error that caused the failure should be near the end of the log file. When build_visit finishes running, it will leave the directories that it used to build the packages intact. You can go into the directory of the package that failed and correct the issue and finish building and installing the package. You can then execute the build_visit command again to have it continue the build.