#1 Problem with dgesv and IBM JIT compiler


The Dgesv.dgesv routine from JLAPACK 0.6 doesn't work
consistently correctly under IBM's Linux JRE with the
following version:

$ java -version
java version "1.3.0"
Java(TM) 2 Runtime Environment, Standard Edition (build
Classic VM (build 1.3.0, J2RE 1.3.0 IBM build
cx130-20010626 (JIT enabled: jitc))

Apparently it is a bad interaction with the JIT
compiler because the routine gives a correct answer the
first time it is called but eventually starts giving
incorrect answers. I have appended a small test
program written in Jython that demonstrates the
problem. The program solves a 3x3 matrix equation
10001 times using Dgesv.dgesv and prints the results of
the first and last attempts. The answers should be
identical but are not. The first result is correct.

$ jython jlapack_test.py
Result first attempt: 0
v[0] = -0.08293070351379606
v[1] = 0.09266920225961406
v[2] = -0.001722128614625683

Result 10000th attempt: 0
v[0] = 22.200877727061638
v[1] = 1749.617616670161
v[2] = 1.302740822326132

For this project, turning off the JIT is not an
option. Nor is switching to another JRE. Therefore
our ability to use JLAPACK depends on finding a way
around this bug.

Let me know if there is any more information that I can
give you to help diagnose this problem.



  • Michael Haggerty

    Jython script demonstrating error

  • Keith Seymour

    Keith Seymour - 2003-02-04
    • status: open --> closed
  • Keith Seymour

    Keith Seymour - 2003-02-04

    Logged In: YES

    This does in fact seem to be a bug with the IBM
    jit in version 1.3 since upgrading to 1.4 works.
    However, for those who do not want to or cannot
    upgrade to 1.4, the attached jar file works with

  • Keith Seymour

    Keith Seymour - 2003-02-04

    Logged In: YES

    Regarding my previous comment, the jar file
    could not be attached here because it was
    too large. So I uploaded the file to the
    "Downloads" area under the Support release.
    The file name is "jla_ibm13.tgz".


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