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[Scalapack] scalapack-1.8.0 bug report


during some internal tests at IBM with the XL compilers on POWER6/7, we 
believe we have found a bug in the following files : 


IROFFZ and IZROW are not initialized in case WANTZ evaluates to .FALSE. 
With aggressive compiler optimizations, these unitialized variables will 
not necessarily be 0 and could (and do) take any value leading to errors 
further down. A possible outcome would be, for the xdsep test for example 

{ 0, 0}: On entry to PDSYEV parameter number 10 had an illegal value
{ 0, 0}: On entry to PDSYEV parameter number 10 had an illegal value
PDSYEV returned INFO= -10
PDSYEV failed the |AQ -QE| test
PDSYEV failed the |QTQ -I| test 

but we've had much worse failures : segfaults and even MPI hangs that we 
are still investigating.

I wish there would be a tool to warn about the use of possibly unitialized 

FTNCHEK Version 3.3 November 2004, finds a few "set but unused variables" 
but that's all.

FTNCHEK Version 3.3 November 2004

File pdsyev.f:

Warning in module PDSYEV in file pdsyev.f: Variables set but never used:
    FIVE set at line 245 file pdsyev.f
    IERRCLS set at line 247 file pdsyev.f
    IERREBZ set at line 248 file pdsyev.f
    IERREIN set at line 247 file pdsyev.f
    IERRSPC set at line 247 file pdsyev.f
    MB_Z set at line 339 file pdsyev.f
    NB_Z set at line 338 file pdsyev.f
    TEN set at line 245 file pdsyev.f


Online Fortran checkers like or didn't do a better job.

Dr. Francois THOMAS, IBM Certified Professional, Deep Computing Europe, 
Tel : (33)-4-67344061, GSM : (33)-6-83258855 Fax : (33)-4-67346477
ft@Domain.Removed, ICQ# 95392338, gpg --keyserver --recv-keys 

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