The paper considers the model of a parallel program, which can be effectively interpreted using an instrumental computer, allowing for fairly exact prediction of the actual runtime of a parallel program on a specific parallel computing system. The model has been developed for parallel Java-programs with explicit exchange of messages by means of the MPI library. The model is part of the ParJava environment. The model is derived by converting the program control tree, which, for the Java-program, can be built by modifying the abstract syntax tree. Communication functions are modeled by using the LogGP model, allowing to account for the specific features of a distributed computational system.