CharmLite

Status:

• Requires that ${env:CHARM_HOME} points to a valid Charm++ build.
  • The lightest possible build is: ./build AMPI-only <triplet> <compiler>? --with-production -DCSD_NO_IDLE_TRACING=1 -DCSD_NO_PERIODIC=1
  • Binaries should be compiled with -fno-exceptions -fno-unwind-tables to further minimize overheads.
  • Requires a valid Charm++ while building Charmlite (can be appended to CMAKE_PREFIX_PATH)
• Only tested with non-SMP builds, SMP builds currently crash:
  • This can be fixed by correctly isolating globals as Csv/Cpv.
  • Probably fixed but needs more testing.
• Uses Hypercomm distributed tree creation scheme for chare-array collectives:
  • Google doc write-up.
  • Hypercomm implementation.
• Add support for "location records" that indicate migratibility.
  • How should users specify whether elements can/not migrate?

Build Instructions:

To build charmlite, the following dependencies are required:

• A valid charm install and ${env:CHARM_HOME} set to it.
• A cmake version higher than or equal to 3.16
• A fully conforming C++17 compiler

Charmlite doesn't support in-source tree builds. The easiest way to build charmlite is as follows:-

$ git clone https://github.com/UIUC-PPL/charmlite
$ cd charmlite && mkdir build && cd build
$ cmake -DCMAKE_INSTALL_PREFIX=<installation directory> -DCMAKE_PREFIX_PATH=<Charm++ installation directory> ..
$ make -j$(nproc)
$ make install

Other than the default cmake flags, Charmlite supports various options that the user can enable using cmake:-

1. CHARMLITE_ENABLE_EXAMPLES - Enables building examples (default: ON)
2. CHARMLITE_ENABLE_TESTS - Enables building and testing tests (default: OFF)
3. CHARMLITE_ENABLE_BENCHMARKS - Enables building and testing benchmarks (default: OFF)
4. CHARMLITE_BENCHMARK_PE - PE argument passed to tests (default: 2)
5. CHARMLITE_BENCHMARK_PPN - PEs per node passed to tests (default: 2)

Using Charmlite in dependant applications:

Users can use charmlite in an application that depends on it. A basic example is as follows:-

Consider the following basic directory structure:-

$ tree my_application
my_application
├── CMakeLists.txt
└── pgm.cpp

The following inclusions to CMakeLists.txt are crucial:-

cmake_minimum_required(VERSION 3.16)

project(CharmLite CXX)

find_package(CharmLite)

add_executable(pgm pgm.cpp)
target_link_libraries(pgm PUBLIC CharmLite::charmlite)

The notable additions to CMakeLists.txt here are find_package(CharmLite) and target_link_libraries(<target> PUBLIC CharmLite::charmlite). find_package tries to find charmlite installation while linking CharmLite::charmlite ensures proper headers and libraries pertaining to charmlite are included and linked.

To build:

$ make build && cd build
$ cmake -DCMAKE_PREFIX_PATH=<path to charmlite installation> ..
$ make

Adding installation path to CMAKE_PREFIX_PATH allows cmake to find charmlite and set various charmlite related cmake flags.

Overall

Overall... need more examples; feel free to try porting your favorite example. Agenda:

• Jacobi2d
• Cannon's Matrix-Matrix Multiplication (Justin)
• FFT (Tree-based)
• FEM