Basic HTML version of Foils prepared Sept 30 1998

Foil 15 Numerical Computing in Java

From Java Grande (a.k.a. Java for High Performance Computing) in a Nutshell Sun MicroSystems Java Day at CMU Pittsburgh -- Sept 26 1998. by Geoffrey C. Fox


So Java not only will run anywhere but can be expected to get same answers everywhere
  • As long as use of Native (C, Fortran) libraries and indeterminate concurrency controlled
Natural tension between performance (both in terms of speed and precision) and reproducibility
  • Need to encourage more research into "reproducible algorithms" but support both goals
Java has particularly bad floating point performance due to
  • As in all applications, immature compiler (JIT) technology
  • does not exploit proprietary hardware features (extended precision, fused multiply add)
  • does not allow well known compiler optimizations (associativity)
Solution requires "Change in Java Rules" and better compilers



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