Basic HTML version of Foils prepared October 2 1998

Foil 16 Java Rules for Floating Point

From Java Grande (a.k.a. Java for High Performance Computing) in a Nutshell Sun MicroSystems Java Day at MIT (Marriot Hotel Cambridge MA) -- Sept 25 1998. by Geoffrey C. Fox


1 Java is particularly slow on floating point -- why?
  • Immature Compiler and library Technology
  • Does not Exploit optimally hardware on PowerPC and Intel platforms
    • Current Java rules optimized for SPARC architecture .....
  • Does not use well known compiler optimizations for blocking, unrolling, reorganizing expressions
2 Current Java rules imply that if careful (avoid indeterminate threads and use of JNI) Java not only runs everywhere but gets identical results everywhere
3 Need to study Reproducibility -- Performance Trade-offs
  • Maybe people have emphasized performance too much but you are not going to change their minds quickly -- should be tolerant of all perceived needs
  • Note current Java is both lower precision AND lower performance than other languages

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