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


From: Gerald Kasner
Subject: Re: Fwd: gm2 frontend in gcc 14 (fedora 40) bug
Date: Tue, 30 Apr 2024 21:15:31 +0200
User-agent: Mozilla Thunderbird

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

Attachment: testgauss.mod
Description: audio/mod


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