Re: Fwd: gm2 frontend in gcc 14 (fedora 40) bug

[Gerald Kasner]

Hi Gaius,

more on this...if one changes the type of the loop variables from
cardinal to integer, the program runs fine.

For me it, seems a conflict of types in a loop variable:

In my understanding, I can count down a cardinal variable down to zero
by a (noncardinal negative step) down to zero.
Am I wrong?

Best, Gerald

Am 30.04.24 um 21:15 schrieb Gerald Kasner:
> Hi Gaius,
>
> I nailed it down to the back substitution loop over i:
> (The old fashioned way)
> The loop does not go down to 1 but exits at (in this case) at i=4.
>
> I indicated the section in the attached code.
> I hope this helps.
>
> Best, Gerald
>
>
> Am 29.04.24 um 19:59 schrieb Gaius Mulley:
> > Gerald Kasner <gerald.kasner@ovgu.de> writes:
> >
> > > Hi Gaius,
> > >
> > >
> > > a quick test with gm2 (GCC) 14.0.1 20240411 (Red Hat 14.0.1-0) gave
> > >
> > > wrong results with a simple Gaussian elimination, while older 
> > > gm2-frontends
> > >
> > > (gm2 (GCC) 13.2.1 20240316 (Red Hat 13.2.1-7)) give correct results
> > >
> > > test compiled with:
> > >
> > > gm2 -O2 -fiso testgauss.mod -lm
> > >
> > > Result with version 13.2.1 :
> > >
> > >        125.000000000000369482222595252097
> > >      -2880.000000000007275957614183425903
> > >      14490.000000000032741809263825416565
> > >     -24640.000000000047293724492192268372
> > >      13230.000000000023646862246096134186
> > >
> > > Result with 14.0.1:
> > >
> > >           1.000000000000000000000000000000
> > >          1.500000000000000000000000000000
> > >          1.166666666666666740681534975010
> > >     -24640.000000000047293724492192268372
> > >      13230.000000000023646862246096134186
> > >
> > > With  pivoted Gaussian elimination, the first three are NaN's.
> > >
> > > Any idea's ???
> > >
> > > testgauss.mod is attached here.
> > >
> > > Regards, Gerald
> > Hi Gerald,
> >
> > many thanks for the bug report - now under investigation.  I tried the
> > usual trick of:
> >
> > $ gm2 -fiso -fm2-whole-program -fsoft-check-all -O0 testgauss.mod
> >
> > but no runtime error was detected - I'm going to try check pointing next
> > (against gm2-13),
> >
> > regards,
> > Gaius