Brought to you by the High Performance and Dependable Computing Systems (HPDCS) at Sapienza, University of Rome

The ROme OpTimistic Simulator is an x86-64 Open Source, multithreaded parallel simulation platform developed using C/POSIX technology. It transparently supports all the mechanisms associated with parallelization (e.g., mapping of simulation objects on different kernel instances) and optimistic synchronization (e.g., state recoverability).

The programming model supported by ROOT-Sim allows the simulation model developer to use a simple application-callback function named ProcessEvent() as the event handler, whose parameters determine which simulation object is currently taking control for processing its next event, and where the state of this object is located in memory. An object is a data structure, whose state can be scattered on dynamically allocated memory chunks, hence the memory address passed to the callback locates a top level data structure implementing the object state-layout.

ROOT-Sim's development started as a research project late back in 1987, and is currently run by the High Performance and Dependable Computing Systems group at the Dipartimento di Ingegneria Informatica, Automatica e Gestionale, Sapienza, University of Rome.

This version of ROOT-Sim stands as the latest development branch of the simulator. Currently, it supports a high-performance multithreaded execution on multicore environments. The goal of this ultimate version of the simulator is to port all the lessons learned during almost 30 years of research on more modern multicore architectures. While the current version still does not allow to run on distributed environments, it will in the near future, after that many low-level optimizations are completed.

This new version strives to be as backwards compatible as possible, letting all the historic simulation models developed on ROOT-Sim be compatible, although some recent changes in the simulator's architecture require minor modifications to the original models' sources (which are nevertheless being updated in the current branch).

ROOT-Sim uses autotools to provide an installation workflow which is common for all supported platforms. This repository does not provide already-generated installation scripts (while released tarballs do), rather we provide the convenience autogen.sh script which should build everything on the target machine. Using autotools, autoconf, automake and libtoolize are required to let autogen.sh generate the correct configure script.

Briefly, the shell commands ./configure; make; make install should configure, build, and install this package. Also, you can also type make uninstall to remove the installed files.

By default, make install installs the package's commands under /usr/local/bin, include files under /usr/local/include, etc. You can specify an installation prefix other than /usr/local by giving configure the option --prefix=PREFIX, where PREFIX must be an absolute path name.

ROOT-Sim uses many gcc extensions, so the currently supported compiler is only gcc.

When running the simulation model, ROOT-Sim allocates a separate stack for each Logical Process, so as to completely separate their execution contexts, using custom User-Level Threads. This could require longer simulation startup time, which could be avoided during model development by passing configure the option --disable-ult

When debugging the platform, it is suggested to pass configure the option --enable-debug to compile the simulator with more strict error checking, and to include all debugging symbols.

When running make install, the rootsim-cc compiler is added to the path.

To compile a simulaton model, simply cd into the project's directory and type rootsim-cc *.c -o model. This will create the model executable, which is the model code already linked with the ROOT-sim library. rootsim-cc ultimately relies on gcc, so any flag supported by gcc can be passed to rootsim-cc.

To test the correctness of the model, it can be run sequentially, typing ./model --sequential --nprc <number of required LPs> This allows to spot errors in the implementation more easily.

Then, to run it in parallel, type ./model --np <number of available Cores> --nprc <number of required LPs>