[Bug 1811798] Re: gcc 8 miscompiles scipy/optimize/minpack/qrsolv.f

[Bug Watch Updater]

Launchpad has imported 1 comments from the remote bug at
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88856.

If you reply to an imported comment from within Launchpad, your comment
will be sent to the remote bug automatically. Read more about
Launchpad's inter-bugtracker facilities at
https://help.launchpad.net/InterBugTracking.

------------------------------------------------------------------------
On 2019-01-15T11:58:06+00:00 Matthias Klose wrote:

seen when build scipy on s390x with the current GCC 8 branch.  According
to the Debian report [1] this is tracked down to miscompilation of one
Fortran file with -funroll-loops. The Ubuntu report [2] has a
"standalone" python test case.

[1] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=915738
[2] https://bugs.launchpad.net/ubuntu/+source/python-scipy/+bug/1811798

Reply at: https://bugs.launchpad.net/ubuntu/+source/python-
scipy/+bug/1811798/comments/1


** Changed in: gcc
       Status: Unknown => New

** Changed in: gcc
   Importance: Unknown => Medium

-- 
You received this bug notification because you are a member of Ubuntu
Foundations Bugs, which is subscribed to gcc-8 in Ubuntu.
https://bugs.launchpad.net/bugs/1811798

Title:
  gcc 8 miscompiles scipy/optimize/minpack/qrsolv.f

Status in gcc:
  New
Status in gcc-8 package in Ubuntu:
  New
Status in imexam package in Ubuntu:
  New
Status in python-scipy package in Ubuntu:
  New
Status in python-scipy package in Debian:
  New

Bug description:
  Originally reported in https://bugs.debian.org/906198

  The following simple test fails on s390x:

  ---------------------------8<------------------------------
  import numpy as np
  from scipy.optimize import leastsq

  y = np.array([0., 1., 1., 2., 1., 1., 0.])
  x = np.arange(len(y))

  def func(par):
      return par[2] * np.exp(-(x - par[0])**2/par[1]) - y

  print(leastsq(func, [0,1,0]))
  ---------------------------8<------------------------------

  The expected result is

  (array([3.        , 4.42280548, 1.67210345]), 1)

  while on S390x, one gets

  (array([0.        , 1.        , 0.34027645]), 3)

  
  Further information from https://bugs.debian.org/915738

  The bug seems to be a miscompilation of scipy/optimize/minpack/qrsolv.f
  with -funroll-loops. Removing -funroll-loops is enough to get the
  leastsq testcase to pass.

To manage notifications about this bug go to:
https://bugs.launchpad.net/gcc/+bug/1811798/+subscriptions