So if I accumulate them from the extra points in gradsum, but then only
apply to atoms that are not extra points, we are good?
On Fri, May 22, 2020 at 1:29 PM David Cerutti <dscerutti.gmail.com> wrote:
> Our emails may have crossed in writing, but it appears that in both CPU and
> GPU codes the netfrc is being subtracted after extra points have had their
> forces transmitted to their massive frame atoms. The solutions to dealing
> with the pollution that netfrc correction causes with extra points differ
> in each code.
>
> Dave
>
>
> On Fri, May 22, 2020 at 4:27 PM Scott Le Grand <varelse2005.gmail.com>
> wrote:
>
> > Cool, and if it's an extra point should I or should I not subtract the
> > netfrc? Dumb questions asked upfront to save time later?
> >
> > On Fri, May 22, 2020 at 1:20 PM <cancersimulation.gmail.com> wrote:
> >
> > > It is static. Usually, it should be the same as "numextra" here
> > >
> > > use prmtop_dat_mod, only : numextra
> > >
> > > I believe Dave Cerutti has implemented some extra-point stuff and I
> don't
> > > know if the above statement still holds with his stuff.
> > >
> > > Taisung
> > >
> > > -----Original Message-----
> > > From: Scott Le Grand [mailto:varelse2005.gmail.com]
> > > Sent: Friday, May 22, 2020 3:02 PM
> > > To: AMBER Developers Mailing List <amber-developers.ambermd.org>
> > > Subject: Re: [AMBER-Developers] Faster NetFrc
> > >
> > > So also...
> > >
> > > I would assume the value of "ignored" is static. How do I calculate it
> a
> > > priori? And it looks like I don't apply it to the extra points. Feel
> free
> > > to
> > > describe off-list, but I want to drill down deep and get this right on
> > the
> > > first swing...
> > >
> > > On Thu, May 21, 2020 at 6:08 PM Scott Le Grand <varelse2005.gmail.com>
> > > wrote:
> > >
> > > > Excellent, that makes this much more straightforward. Should have
> > > > something by early next week.
> > > >
> > > > On Thu, May 21, 2020 at 6:04 PM <taisung.gmail.com> wrote:
> > > >
> > > >> The force thresholds are for those "dummies" (not the alchemical
> > > >> dummies but something like lone-pair points of water models). The
> > > >> forces of those atoms are "transferred" to other real atoms at the
> > > >> final force collection stage--and hence need to be kept to zero
> > > >> during the netfrc stage. Of course, you may find better ways to do
> > > >> things. For example, as Scott mentioned, the only non-conserved
> > > >> force part is PME reciprocal part. If the netfrc is done in the PME
> > > >> reciprocal part, there is no need to have such force thresholds.
> > > >>
> > > >> Taisung
> > > >>
> > > >> -----Original Message-----
> > > >> From: David Cerutti [mailto:dscerutti.gmail.com]
> > > >> Sent: Thursday, May 21, 2020 8:37 PM
> > > >> To: AMBER Developers Mailing List <amber-developers.ambermd.org>
> > > >> Subject: Re: [AMBER-Developers] Faster NetFrc
> > > >>
> > > >> As implied, the GTI code is the revision that introduced this.
> > > >> Taisung can comment more on his logic, but the presence of this
> > > >> "small" term reminds me of something he's got in the non-bonded
> inner
> > > >> loop as well. I'm not sure we ever determined why these
> conditionals
> > > >> were needed; I think the one in the non-bonded loop should just go
> > > >> away after some other revisions I made, but I'll wait for more
> input.
> > > >>
> > > >> Dave
> > > >>
> > > >>
> > > >> On Thu, May 21, 2020 at 8:29 PM Scott Le Grand
> > > >> <varelse2005.gmail.com>
> > > >> wrote:
> > > >>
> > > >> > Hey guys,
> > > >> > Back as an AMBER developer and one of the first things I'd like to
> > > >> > do is optimize netfrc.
> > > >> >
> > > >> > Fixed point conservative forces have no net force. They
> > > >> > automagically cancel out 100%. So we can ignore everything except
> > > >> > non-conserved
> > > >> forces.
> > > >> >
> > > >> > The only non-conserved force I know of is the Ewald Gradient Sum.
> > > >> > So if I add up the net force there, and handle it upon either
> force
> > > >> > reduction or update, I can eliminate two passes on memory and the
> > > >> > two kernels currently dedicated to adding and then subtracting
> them.
> > > >> >
> > > >> > But... Are there any other non-conserved forces?
> > > >> >
> > > >> > And... It looks like the FORTRAN and the CUDA code do different
> > > things.
> > > >> > FORTRAN simply averages the forces and subtracts. But CUDA only
> > > >> > averages over atoms with force thresholds above a predefined small
> > > >> > amount. What's up with that?
> > > >> >
> > > >> > pme_ene.F90:
> > > >> > if (netfrc .gt. 0 .and. onstep) then
> > > >> >
> > > >> > if (ti_mode .eq. 0) then
> > > >> > do i = 1, atm_cnt
> > > >> > net_frcs(:) = net_frcs(:) + frc(:, i)
> > > >> > end do
> > > >> >
> > > >> > ! Now do the correction:
> > > >> >
> > > >> > net_frcs(:) = net_frcs(:) / dble(atm_cnt - numextra)
> > > >> >
> > > >> > do i = 1, atm_cnt
> > > >> > frc(:, i) = frc(:, i) - net_frcs(:)
> > > >> > end do
> > > >> > else
> > > >> > do i = 1, atm_cnt
> > > >> > ti_net_frcs(1, :) = ti_net_frcs(1, :) + ti_nb_frc(1, :,
> i)
> > > >> > ti_net_frcs(2, :) = ti_net_frcs(2, :) + ti_nb_frc(2, :,
> i)
> > > >> > end do
> > > >> >
> > > >> > ti_net_frcs(1,:) =
> > > >> > ti_net_frcs(1,:)/dble(ti_atm_cnt(1)-ti_numextra_pts(1))
> > > >> > ti_net_frcs(2,:) =
> > > >> > ti_net_frcs(2,:)/dble(ti_atm_cnt(2)-ti_numextra_pts(2))
> > > >> > net_frcs(:) = ti_net_frcs(1,:) + ti_net_frcs(2,:)
> > > >> >
> > > >> > do i = 1, atm_cnt
> > > >> > ! This matches how sander removes netfrcs in TI runs
> > > >> > if (ti_lst(1,i) .ne. 0) then
> > > >> > frc(:, i) = frc(:, i) - ti_net_frcs(1,:)
> > > >> > else if (ti_lst(2,i) .ne. 0) then
> > > >> > frc(:, i) = frc(:, i) - ti_net_frcs(2,:)
> > > >> > else
> > > >> > frc(:, i) = frc(:, i) - net_frcs(:)
> > > >> > end if
> > > >> > end do
> > > >> > end if
> > > >> > ! Any extra points must have their 0.d0 forces reset...
> > > >> >
> > > >> > if (numextra .gt. 0 .and. frameon .ne. 0) &
> > > >> > call zero_extra_pnts_vec(frc, ep_frames, gbl_frame_cnt)
> > > >> >
> > > >> > end if
> > > >> >
> > > >> >
> > > >> > GTI path:
> > > >> > while (pos < cSim.atoms) {
> > > >> > PMEFloat fx = converter(pX[pos], ONEOVERFORCESCALE);
> > > >> > PMEFloat fy = converter(pY[pos], ONEOVERFORCESCALE);
> > > >> > PMEFloat fz = converter(pZ[pos], ONEOVERFORCESCALE);
> > > >> > if (abs(fx) > small || abs(fy) > small || abs(fz) > small) {
> > > >> > pX[pos] -= nfX;
> > > >> > pY[pos] -= nfY;
> > > >> > pZ[pos] -= nfZ;
> > > >> > }
> > > >> > pos += increment;
> > > >> > }
> > > >> >
> > > >> > Scott
> > > >> > _______________________________________________
> > > >> > AMBER-Developers mailing list
> > > >> > AMBER-Developers.ambermd.org
> > > >> > http://lists.ambermd.org/mailman/listinfo/amber-developers
> > > >> >
> > > >> _______________________________________________
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> > > >>
> > > >>
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> > > >> AMBER-Developers.ambermd.org
> > > >> http://lists.ambermd.org/mailman/listinfo/amber-developers
> > > >>
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> > >
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Received on Fri May 22 2020 - 14:00:02 PDT
