G. History

The C HARM software was developed as a group effort of the Parallel Programming Laboratory at the University of Illinois at Urbana-Champaign. Researchers at the Parallel Programming Laboratory keep Charm++ updated for the new machines, new programming paradigms, and for supporting and simplifying development of emerging applications for parallel processing. The earliest prototype, Chare Kernel(1.0), was developed in the late eighties. It consisted only of basic remote method invocation constructs available as a library. The second prototype, Chare Kernel(2.0), a complete re-write with major design changes. This included C language extensions to denote Chares, messages and asynchronous remote method invocation. C HARM (3.0) improved on this syntax, and contained important features such as information sharing abstractions, and chare groups (called Branch Office Chares). C HARM (4.0) included Charm++ and was released in fall 1993. Charm++ in its initial version consisted of syntactic changes to C++ and employed a special translator that parsed the entire C++ code while translating the syntactic extensions. C HARM (4.5) had a major change that resulted from a significant shift in the research agenda of the Parallel Programming Laboratory. The message-driven runtime system code of the Charm++ was separated from the actual language implementation, resulting in an interoperable parallel runtime system called C ONVERSE . The Charm++ runtime system was retargetted on top of C ONVERSE , and popular programming paradigms such as MPI and PVM were also implemented on C ONVERSE . This allowed interoperability between these paradigms and Charm++. This release also eliminated the full-fledged Charm++ translator by replacing syntactic extensions to C++ with C++ macros, and instead contained a small language and a translator for describing the interfaces of Charm++ entities to the runtime system. This version of Charm++, which, in earlier releases was known as Interface Translator Charm++ , is the default version of Charm++ now, and hence referred simply as Charm++ . In early 1999, the runtime system of Charm++ was rewritten in C++. Several new features were added. The interface language underwent significant changes, and the macros that replaced the syntactic extensions in original Charm++, were replaced by natural C++ constructs. Late 1999, and early 2000 reflected several additions to Charm++ , when a load balancing framework and migratable objects were added to Charm++ .