Isaac Lopez

Development of CORBA-based engineering applications from legacy Fortran programs

Abstract A majority of scientific and engineering applications in aerodynamics and solid mechanics are written in Fortran. To reduce the high cost of software development, NASA researchers reuse most of the legacy Fortran codes instead of developing them from scratch in the numerical propulsion system simulation project. In this paper, we present an efficient methodology for integrating legacy applications written in Fortran into a distributed object framework. Issues and strategies regarding the conversion and wrapping of Fortran codes into common object request broker architecture objects are discussed. Fortran codes are modified as little as possible when they are decomposed into modules and wrapped as objects. We implement a wrapper generator which takes the Fortran application as input and generates the C++ wrapper files and interface definition language file. Tedious programming tasks for wrapping the codes can therefore be reduced.

A space-based end-to-end prototype geographic information network for lunar and planetary exploration and emergency response (2002 and 2003 field experiments)

Communications and imaging experiments conducted in the Arizona desert during July of 2002 with the National Aeronautics and Space Administration (NASA) and the United States Geological Survey (USGS) helped to identify a fundamental suite of scientific instruments focused on surface composition and temperature determination for the calibration and validation of NASA and USGS spaceborne and airborne sensors and to integrate them with a hybrid mobile wireless and satellite network for lunar and planetary exploration and emergency response. The 2002 experiment focused on the exchange of remotely sensed and ground truth geographic information between analysts and field scientists. That experiment revealed several modifications that would enhance the performance and effectiveness of geographic information networks (GIN) for lunar and planetary exploration and emergency response. Phase 2 experiments conducted during June 2003 at the USGS Earth Resources and Observation Systems (EROS) Data Centers geologic imaging test site near Dinosaur National Monument in the NE Utah desert incorporated several of the lessons learned from the 2002 experiment and successfully added five major new components: (1) near-real-time hyperspectral and multispectral satellite image acquisition, (2) remotely controlled and coordinated mobile real-time ground sensor measurements during the imaging satellite overpass, (3) long-delay optimized Transmission Control Protocol/Internet Protocol TCP/IP protocols to improve network performance over geosynchronous communications satellite circuits, (4) distributed, multinode parallel computing on NASAs Internet Power GRID (IPG), and (5) near-real-time validation of satellite imagery as part of a successful test of the NASA-USGS National Emergency Mapping Information System.

Migrating legacy scientific applications towards CORBA-based client-server architectures

A distributed object is a reusable, self‐contained piece of software that cooperates with other objects on the same machine or across a network in a plug‐and‐play fashion via a well‐defined interface. The Numerical Propulsion System Simulation (NPSS) attempts to provide a collaborative aircraft engine design and simulation environment based on this concept. Many scientific applications in aerodynamics and solid mechanics are written in Fortran. Refitting this legacy Fortran code with distributed objects can increase code reusability. In this paper, we focus on the novel use of a remote variable scheme to help programmers migrate the Fortran code towards a client–server architecture. This scheme gives the client the capability of accessing variables at the server site and makes it easier for programmers to couple component engine code. Through the operator overloading features in C++, remote variables can be used in much the same way as traditional variables. The remote variable scheme adopts the lazy update approach and the prefetch method. Preliminary performance evaluation shows that communication overhead can be greatly reduced. Copyright

A CORBA-Based Distributed Component Environment for Wrapping and Coupling Legacy Scientific Codes

Within NASAs High Performance Computing and Communication (HPCC) program, the NASA Glenn Research Center (GRC) is developing a large scale, detailed simulation environment for the analysis and design of aircraft engines called the Numerical Propulsion System Simulation (NPSS). The three major aspects of modeling capabilities focused in NPSS, including integration of different engine components, coupling of multiple disciplines, and engine component zooming at appropriate level of fidelity, require relatively tight coupling of different analysis codes. Most of these codes in aerodynamics and solid mechanics are written in Fortran. Refitting these legacy Fortran codes with distributed objects can increase these codes reusability. In this paper, we describe our experiences in building a CORBA-based component development environment for programmers to easily wrap and couple legacy Fortran codes. This environment consists of a C++ wrapper library to hide the details of CORBA and an efficient remote variable scheme to facilitate data exchange between the client and the server. We also report empirical performance evaluation results and describe current applications.

CORBA wrapping of legacy scientific applications using remote variable scheme

A distributed object is a reusable, self-contained piece of software that cooperates with other objects on the same machine or across a network in a plug-and-play fashion via a well-defined interface. The Numerical Propulsion System Simulation (NPSS) attempts to provide a collaborative aircraft engine design and simulation environment based on this concept. Many scientific applications in aerodynamics and solid mechanics are written in Fortran. Refitting these legacy Fortran codes with distributed objects can increase the code reusability. The remote variable scheme provided in NPSS helps programmers easily migrate the Fortran codes towards a client-server platform. This scheme gives the client the capability of accessing the variables at the server site. Through the operator overloading features in C++, remote variables can be used in much the same way as traditional variables. The remote variable scheme adopts the lazy update approach and the prefetch method. Preliminary performance evaluation shows that communication overhead can be greatly reduced.