Basic HTML version of Foils prepared 16 May 98

Foil 53 Java Features -- High Performance

From Introduction to Java to be used in (Scientific) Computing CEWES Java Tutorial -- Spring Semester 98. by Geoffrey C. Fox, Nancy McCracken


1 Java interpreter performs on-the-fly runtime execution of the Java bytecodes which results typically in a satisfactory performance.
  • NOT true in initial software which is often 50 times slower than C
  • see http://www.netlib.org/benchmark/linpackjava/
  • performance is improved in new "just-in-time" interpreters, which saves code for repeated sections to provide compiled code efficiency after first execution
  • JIT compilers should be 2 to 4 times slower than classic compiled code
2 Support for generating native machine code out of Java bytecodes, viewed as intermediate compiler form, is also provided and useful for performance demanding applications.
  • Can "decompile" bytecodes back to Java quite easily
3 The performance of the machine code, generated directly by native compiler from Java or its bytecodes, should be comparable to that offered by typical Fortran/C/C++ compilers on the same platform.
4 .

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