You are right, this is a bug (potentially severe). In my local version I replaced somm with a more standard integration as somm interpolates to the origin (which is not right).
On Wed, May 9, 2018 at 2:11 PM, Pavel Ondračka <pavel.ondra...@email.cz> wrote: > ---------- Původní e-mail ---------- > Od: Laurence Marks <l-ma...@northwestern.edu> > Komu: A Mailing list for WIEN2k users <wien@zeus.theochem.tuwien.ac.at> > Datum: 9. 5. 2018 18:18:21 > Předmět: Re: [Wien] IEEE_UNDERFLOW_FLAG IEEE_DENORMAL > > Zamt is set by somm, which is a slightly inaccurate Simpson summation (the > accuracy does not matter). Hence it does not need to be set previously. > > > Right, it is indeed set in the somm subroutine. The problem is that the DA > variable (the local name for zamt variable in the somm subroutine) is set > for the first time on line 11, while it is used (read) for the first time > earlier on line 10 (and this is the line when the gcc and valgrind > complains)! Hence when the subroutine is called for the first time, the > results depends on read from uninitialized memory. > > Best regards > > Pavel > > > > > _____ > Professor Laurence Marks > "Research is to see what everybody else has seen, and to think what nobody > else has thought", Albert Szent-Gyorgi > www.numis.northwestern.edu > > On Wed, May 9, 2018, 10:42 AM Pavel Ondračka <pavel.ondra...@email.cz> > wrote: > > Laurence Marks píše v St 09. 05. 2018 v 11:51 +0000: > > This appears to be due to a silly approach in gfortran, and almost > > certainly is not an error/problem and can be ignored -- see > https://urldefense.proofpoint.com/v2/url?u=https-3A__s&d=DwIGaQ&c= > yHlS04HhBraes5BQ9ueu5zKhE7rtNXt_d012z2PA6ws&r=U_ > T4PL6jwANfAy4rnxTj8IUxm818jnvqKFdqWLwmqg0&m=R1lxmwh4Y3r4yRx1ZyR4NN9mpSe7Ru > aT974qRm6Uhfw&s=KDobN5dacXxTk7OUpO1BdJBY45FBX34Hf6Q9hTempg0&e= > > tackoverflow.com/questions/44308577/ieee-underflow-flag-ieee- > <https://urldefense.proofpoint.com/v2/url?u=http-3A__tackoverflow.com_questions_44308577_ieee-2Dunderflow-2Dflag-2Dieee-2D&d=DwMFaQ&c=yHlS04HhBraes5BQ9ueu5zKhE7rtNXt_d012z2PA6ws&r=U_T4PL6jwANfAy4rnxTj8IUxm818jnvqKFdqWLwmqg0&m=UwZ1bSYK6i7lR0yGpC7Hknoy6JY6oBi3nk1UgjeA0DI&s=oXUXMikarmZPWkv9fORKiLM0LSpZVQPZ_CslUzYPWfY&e=> > > denormal-in-fortran-77. > > > > While I do agree that in most cases this is harmless, it can also > suggest a bug. > > I only looked at dstart for the TiC and I have this specific example: > > dstart for a TiC case prints a "Note: The following floating-point > exceptions are signalling: IEEE_DENORMAL" line. If you trap this with > -ffpe-trap='denormal' flag, to inspect in gdb, the offending line is > then: > Program received signal SIGFPE, Arithmetic exception. > 0x000000000041dc48 in somm (dr=..., dp=..., dpas=0.013585429144994965, > da=1.1588924125005173e-310, m=0, np=935) at somm.f:10 > 10 D1=DA+MM > > so this line looks completely harmless and some prints show why the > compiler notes about this: > > (gdb) print DA > $1 = 1.1588924125005173e-310 > (gdb) print MM > $2 = 1 > > i.e. we just add a really small number (denormal, since DOUBLE_MIN is > around 1.8e-308) to 1, which is completely OK. But lets take a look > where this incredibly small value comes from... > > (gdb) up > #1 0x00000000004143c6 in make_spheres (lcore=.FALSE., luse=7) at > make_spheres.F:81 > 81 call > somm(rat(1,ia),rhoat(1,ia),dx(ia),zamt,0,nptat(ia)) > > So this is the zamt variable, surprisingly grepping around for zamt > finds nothing. As far as I can see it is not declared or initialized > anywere in dstart. If I just missed something please correct me! The > same goes for the zamt1 and zamt2. > > Note that in this case we get lucky since the random memory value is > effectively zero, however this might in my opinion lead to problems if > you hit random memory with another value. > In fact running the dstart in vagrind shows this as well and the > terminal is spammed with "Conditional jump or move depends on > uninitialised value(s)" and "Use of uninitialised value of size 8". > > IMO this is a bug, so either the line needs to be changed to > somm(rat(1,ia),rhoat(1,ia),dx(ia),0,0,nptat(ia)) > or the zamt variable needs to be declared and initialized somewhere. > But I actually have no idea about the physical meaning of the code so > please correct me if I just missed something. > > Best regards > Pavel > _______________________________________________ > Wien mailing list > Wien@zeus.theochem.tuwien.ac.at > https://urldefense.proofpoint.com/v2/url?u=http-3A__zeus. > theochem.tuwien.ac.at_mailman_listinfo_wien&d=DwIGaQ&c= > yHlS04HhBraes5BQ9ueu5zKhE7rtNXt_d012z2PA6ws&r=U_ > T4PL6jwANfAy4rnxTj8IUxm818jnvqKFdqWLwmqg0&m=R1lxmwh4Y3r4yRx1ZyR4NN9mpSe7Ru > aT974qRm6Uhfw&s=_8Uru9zRH580QrhtgA9HnU1x81x6paXIOqJCFnOzZME&e= > SEARCH the MAILING-LIST at: https://urldefense.proofpoint. > com/v2/url?u=http-3A__www.mail-2Darchive.com_wien- > 40zeus.theochem.tuwien.ac.at_index.html&d=DwIGaQ&c= > yHlS04HhBraes5BQ9ueu5zKhE7rtNXt_d012z2PA6ws&r=U_ > T4PL6jwANfAy4rnxTj8IUxm818jnvqKFdqWLwmqg0&m=R1lxmwh4Y3r4yRx1ZyR4NN9mpSe7Ru > aT974qRm6Uhfw&s=SJYF9VBF7xwkjpCyB76TXcIRXzDcFX3xCQlsoQ4RwIw&e= > > _______________________________________________ > Wien mailing list > Wien@zeus.theochem.tuwien.ac.at > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien > SEARCH the MAILING-LIST at: http://www.mail-archive.com/ > wien@zeus.theochem.tuwien.ac.at/index.html > > -- Professor Laurence Marks "Research is to see what everybody else has seen, and to think what nobody else has thought", Albert Szent-Gyorgi www.numis.northwestern.edu ; Corrosion in 4D: MURI4D.numis.northwestern.edu Partner of the CFW 100% program for gender equity, www.cfw.org/100-percent Co-Editor, Acta Cryst A
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