R-alpha: eigen and batch

Jim Lindsey jlindsey@luc.ac.be
Mon, 25 Aug 1997 09:42:30 +0200 (MET DST)

  Putting q(save=F) at the end of my file does not work in my
context because I can no longer source the file without quitting. I
have that quit statement in my .First so that I always quit that way
interactively. The problem is that it is ignored in batch.

  The crash occurs on my 586 running Red Hat Linux 2.0.27 but not on
my son's 486 running SLackware Linix 2.0.29. We both have the same
most recent libraries installed (libc, libm, etc).
   I started looking in the eispack C code and traced down the
problem. In three of the four Fortran calls in eigen, (ch,rs,cg but
not rg), the same vector (vals) is used for the return eigenvalues as
for two or three temporary workspace vectors. This is risky
programming at any time and leads to a catastrophe with a 586 where
several things may be calculated at the same time. If the variable,
vals, is removed and all use of it in the .Fortran call replaced by
double(n) (as in the call to rg), eigen works on a 586.
  This sort of problem should be checked elsewhere in R.
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