LI76928: COMPILER HANG IN IPA WITH -QHOT=LEVEL=2

November 2012 Update for XL Fortran for Blue Gene/Q, V14.1
February 2013 Update for XL Fortran for Blue Gene/Q, V14.1

APAR status

• Closed as program error.

Error description

• When compiling a large test case with -qhot=level=2, the
  compiler seems to hang causing a long compile time.
  
  ====== Compiler line:
  bgxlf_r -v -g -O3 -qstrict -qhot=level=2 -qsmp=omp
  

Local fix

• Use -qhot=level=1 as a workaround.
  

Problem summary

• An extremely long compile time is seen at -qhot=level=2 for a
  six level nested loop.
  
  Users of -qhot=level=2 when there is a 6-level loop nest with
  certain lower bound and upper bounds are affected by this
  issue.
  It is dependent on the lower bound and upper bounds of the
  loop. In this case the loop is manually tiled.
  
  Polyhedral works on a mathematical representation of loop nests
  in the user program. This representation is modified throughout
  polyhedral framework.
  When a certain algorithm is slow on a specific class of input
  (passed in the form of mathematical representation) it might be
  difficult to translate it back to a class of user programs.
  

Problem conclusion

• The fix involves modifying a loop auto transformation
  optimization, when the number of dimensions of a scop are
  larger than a threshold.
  

Temporary fix

Comments

APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

Fix information

• Fixed component name

  XL FORTRAN FOR

• Fixed component ID

  5799AH100

Applicable component levels

• RE10 PSY

     UP