BROADWAY: A SOFTWARE ARCHITECTURE FOR SCIENTIFIC COMPUTING Samuel Z. Guyer and Calvin Lin The University of Texas

MOTIVATION  Efficient runtime algorithms and efficient memory usage are critical Temps programmers to emphasize performance over clarity Temps programmers to emphasize performance over clarity Often complicates long term maintenance and portability of scientific code. Often complicates long term maintenance and portability of scientific code.  Practitioners of scientific computing are typically unwilling to try novel languages or use sophisticated design methodologies  Deep knowledge of scientific domain is required

BROADWAY COMPILER SYSTEM ARCHITECTURE Library Annotations Header flies Source Code Application Source code Application Source code Integrated and optimized code Integrated and optimized code Broadway Compiler

Performance problems caused by use of software libraries  Different clients have different needs  “Separation of concerns” inhibits information flow across interfaces  Worst case assumptions provide generality at the expense of performance  Modular structure leads to poor resource management  No performance portability  Premature optimization complicates maintenance  Interface bloat defeats modularity

LIBRARY LEVEL OPITIMIZATIONS  Replace general purpose routines with customized routines that run much faster. Can make stronger assumptions about calling context, allowing for more efficient execution Can make stronger assumptions about calling context, allowing for more efficient execution Avoid interface bloat Avoid interface bloat  Use of annotated language to describe domain specific information  Optimization requires application programmer to have little knowledge of library  Broadway compiler can specialize library routines in ways that the library designer did not foresee.

BROADWAY AS A META INTERFACE Application Base Interface Black Box  Use of black boxes leads to performance problems Implementation and interface that black boxes provide will inevitably be inappropriate for some client Implementation and interface that black boxes provide will inevitably be inappropriate for some client

BROADWAY AS A META INTERFACE  Solution: provide 2 interfaces, a base, which most clients use, and a separate meta interface, which allows the black box to adapt to the needs of different clients Application Base Interface Black Box Meta- Interface Meta- Program

Experimental Results Benefit of Automated Approach Tedious transformations can be applied uniformly and completely!

Conclusion  Provided mechanism for improving performance Create different library implementations and interfaces for different clients Create different library implementations and interfaces for different clients Conveys library-specific information to the compiler and use this information to customize the library for different users. Conveys library-specific information to the compiler and use this information to customize the library for different users. Replaces invocations of general routines with invocations of specialized routines, thereby relaxing worst case assumptions. Replaces invocations of general routines with invocations of specialized routines, thereby relaxing worst case assumptions.  Improves the maintenance and portability of applications  Enhances the value of legacy codes  Provides clean division of labor

Discussion  What are the possible downfalls?  Meta-Object Protocols Provide mechanism to change the way a language is compiled. Provide mechanism to change the way a language is compiled.  Future optimizations?