Installation and Dependencies#

Tip

pressio is header-only, so it does not need to be precompiled and linked to. However, since we use preprocessor directives to conditionally enable/disable code based on target third-party libraries, one needs to account for this. See below for the details.

Warning

To use pressio, you need at least a C++17 compiler.

Dependencies#

Some parts of pressio contain code and implementations that are specific to third-party libraries (TPLs). An example is pressio/ops, which contains kernels specializations for widely-used HPC libraries (e.g. Trilinos, Kokkos). The main reason for doing this is that we aim, where possible, to alleviate the user from writing custom operations and allow pressio to decide when and how to leverage the native libraries’ operations to obtain the best performance. This should facilitate the integration and use of pressio by existing applications. This is a growing capability and we currently only provide built-in support to some external HPC libraries (see below). Obviously, these TPLs-specific specializations need to be guarded with preprecessor directives, and enabled only if one can access the TPLs.

Enabling/disabling specific dependencies can be done via the cmake variables listed here.

Optional vs Required#

TPL Name

Optional/Required

Version Known to Work/run in CI

Eigen

Required

3.3.7

Trilinos

Optional

commit: ef73d14babf6e7556b0420add98cce257ccaa56b

MPI

Optional

–

Kokkos

Optional

3.1.0

BLAS

Optional

–

LAPACK

Optional

–

GoogleTest

Optional

1.10.0

Eigen is the only required dependency because it is the default choice for instantiating the ROM data structures and solving the (dense) ROM problem.

In practice, what are the steps to get, install and use Pressio?#

todo: add description for using pressio without configuring, so one has to define the options directly when configuring their code or inside the code directly.

1. Clone pressio (defaults to the main branch), or you can pick a release version

  1. Create a build and install subdirectories

cd <where-you-cloned-pressio>
mkdir build && mkdir install

  1. Use cmake to configure by passing to the comand line the target list of cmake variables to define.

For example, suppose we want to enable support for Trilinos and the debug prints. We would do:

export PRESSIO_SRC=<where-you-cloned-pressio>
cd <where-you-cloned-pressio>/build

cmake -D CMAKE_INSTALL_PREFIX=../install \
      -D PRESSIO_ENABLE_TPL_TRILINOS=ON \
      -D PRESSIO_ENABLE_DEBUG_PRINT=ON \
      ${PRESSIO_SRC}

make install # nothing is built, just headers copied to installation

Note that this step does not build anything because pressio is header-only, but only processes the cmake arguments and copies the pressio headers to the install prefix <where-you-cloned-pressio>/install. If you want, inspect the file <where-you-cloned-pressio>/install/presssio_cmake_config.h which contains the cmake variables configuration.

We also remark that during the configuration step above pressio does not need to know where a target TPL exists in your system. In the configuration step above, you are simply telling Pressio that you have a certain TPL and want to enable the corresponding code in pressio. The TPLs will be needed at linking stage when you build your code that uses pressio.

4. When building your application to use pressio, you just have to point to the installation directory <where-you-cloned-pressio>/install with the installed pressio headers, and you can access all pressio functionalities via the C++ include #include<pressio.hpp>:

#include "pressio/what_you_need.hpp"
// ...
int main(){
 // do something
}

Warning

The procedure above is advised because it enables pressio to properly process the cmake options and turn on/off based on certain conditions (as explained above). The alternative way to use pressio would be to just clone the repo, point to the <where-you-cloned-pressio>/include subdirectory and use cmake variables directly when building your code. However, this could have unexpected consequences since you would be resposible to set the variables correctly but you would not know exactly all the possible constraints.