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(*)Parenthesize continuity_PPM curv_3 expressions
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  Added parentheses to 9 expressions like `curv_3 = h_W(i) + h_E(i) - 2.0*h(i)`
in PPM_limit_pos, zonal_flux_layer, zonal_flux_thickness, merid_flux_layer and
merid_flux_thickness, changing them to `curv_3 = (h_W(i) + h_E(i)) - 2.0*h(i)`.
This change enforces the order of arithmetic that is required to give rotational
symmetry, but it also is the order that the Intel, GNU, and Nvidia compliers
were all already using in these expressions.  Moreover, had the order of
arithmetic ever been anything else, this would have led to failures in our
rotational consistency and redundant point consistency testing, and almost
certainly would have been detected before. However, by adding these parentheses,
there is a remote chance that the addition of these parentheses could change
answers for some compiler or compiler settings we have never tested before.
This change should not impact any FMA-enabled calculations.  All answers are
bitwise identical in the MOM6-examples regression suite as run on Gaea.
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@Hallberg-NOAA
Hallberg-NOAA committed Jul 29, 2024
1 parent 6628dbf commit f0e61f3
Showing 1 changed file with 9 additions and 9 deletions.
18 changes: 9 additions & 9 deletions src/core/MOM_continuity_PPM.F90
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Original file line number Diff line number Diff line change
Expand Up @@ -937,14 +937,14 @@ subroutine zonal_flux_layer(u, h, h_W, h_E, uh, duhdu, visc_rem, dt, G, US, j, &
if (u(I) > 0.0) then
if (vol_CFL) then ; CFL = (u(I) * dt) * (G%dy_Cu(I,j) * G%IareaT(i,j))
else ; CFL = u(I) * dt * G%IdxT(i,j) ; endif
curv_3 = h_W(i) + h_E(i) - 2.0*h(i)
curv_3 = (h_W(i) + h_E(i)) - 2.0*h(i)
uh(I) = (G%dy_Cu(I,j) * por_face_areaU(I)) * u(I) * &
(h_E(i) + CFL * (0.5*(h_W(i) - h_E(i)) + curv_3*(CFL - 1.5)))
h_marg = h_E(i) + CFL * ((h_W(i) - h_E(i)) + 3.0*curv_3*(CFL - 1.0))
elseif (u(I) < 0.0) then
if (vol_CFL) then ; CFL = (-u(I) * dt) * (G%dy_Cu(I,j) * G%IareaT(i+1,j))
else ; CFL = -u(I) * dt * G%IdxT(i+1,j) ; endif
curv_3 = h_W(i+1) + h_E(i+1) - 2.0*h(i+1)
curv_3 = (h_W(i+1) + h_E(i+1)) - 2.0*h(i+1)
uh(I) = (G%dy_Cu(I,j) * por_face_areaU(I)) * u(I) * &
(h_W(i+1) + CFL * (0.5*(h_E(i+1)-h_W(i+1)) + curv_3*(CFL - 1.5)))
h_marg = h_W(i+1) + CFL * ((h_E(i+1)-h_W(i+1)) + 3.0*curv_3*(CFL - 1.0))
Expand Down Expand Up @@ -1019,13 +1019,13 @@ subroutine zonal_flux_thickness(u, h, h_W, h_E, h_u, dt, G, GV, US, LB, vol_CFL,
if (u(I,j,k) > 0.0) then
if (vol_CFL) then ; CFL = (u(I,j,k) * dt) * (G%dy_Cu(I,j) * G%IareaT(i,j))
else ; CFL = u(I,j,k) * dt * G%IdxT(i,j) ; endif
curv_3 = h_W(i,j,k) + h_E(i,j,k) - 2.0*h(i,j,k)
curv_3 = (h_W(i,j,k) + h_E(i,j,k)) - 2.0*h(i,j,k)
h_avg = h_E(i,j,k) + CFL * (0.5*(h_W(i,j,k) - h_E(i,j,k)) + curv_3*(CFL - 1.5))
h_marg = h_E(i,j,k) + CFL * ((h_W(i,j,k) - h_E(i,j,k)) + 3.0*curv_3*(CFL - 1.0))
elseif (u(I,j,k) < 0.0) then
if (vol_CFL) then ; CFL = (-u(I,j,k)*dt) * (G%dy_Cu(I,j) * G%IareaT(i+1,j))
else ; CFL = -u(I,j,k) * dt * G%IdxT(i+1,j) ; endif
curv_3 = h_W(i+1,j,k) + h_E(i+1,j,k) - 2.0*h(i+1,j,k)
curv_3 = (h_W(i+1,j,k) + h_E(i+1,j,k)) - 2.0*h(i+1,j,k)
h_avg = h_W(i+1,j,k) + CFL * (0.5*(h_E(i+1,j,k)-h_W(i+1,j,k)) + curv_3*(CFL - 1.5))
h_marg = h_W(i+1,j,k) + CFL * ((h_E(i+1,j,k)-h_W(i+1,j,k)) + &
3.0*curv_3*(CFL - 1.0))
Expand Down Expand Up @@ -1832,15 +1832,15 @@ subroutine merid_flux_layer(v, h, h_S, h_N, vh, dvhdv, visc_rem, dt, G, US, J, &
if (v(i) > 0.0) then
if (vol_CFL) then ; CFL = (v(i) * dt) * (G%dx_Cv(i,J) * G%IareaT(i,j))
else ; CFL = v(i) * dt * G%IdyT(i,j) ; endif
curv_3 = h_S(i,j) + h_N(i,j) - 2.0*h(i,j)
curv_3 = (h_S(i,j) + h_N(i,j)) - 2.0*h(i,j)
vh(i) = (G%dx_Cv(i,J)*por_face_areaV(i,J)) * v(i) * ( h_N(i,j) + CFL * &
(0.5*(h_S(i,j) - h_N(i,j)) + curv_3*(CFL - 1.5)) )
h_marg = h_N(i,j) + CFL * ((h_S(i,j) - h_N(i,j)) + &
3.0*curv_3*(CFL - 1.0))
elseif (v(i) < 0.0) then
if (vol_CFL) then ; CFL = (-v(i) * dt) * (G%dx_Cv(i,J) * G%IareaT(i,j+1))
else ; CFL = -v(i) * dt * G%IdyT(i,j+1) ; endif
curv_3 = h_S(i,j+1) + h_N(i,j+1) - 2.0*h(i,j+1)
curv_3 = (h_S(i,j+1) + h_N(i,j+1)) - 2.0*h(i,j+1)
vh(i) = (G%dx_Cv(i,J)*por_face_areaV(i,J)) * v(i) * ( h_S(i,j+1) + CFL * &
(0.5*(h_N(i,j+1)-h_S(i,j+1)) + curv_3*(CFL - 1.5)) )
h_marg = h_S(i,j+1) + CFL * ((h_N(i,j+1)-h_S(i,j+1)) + &
Expand Down Expand Up @@ -1919,14 +1919,14 @@ subroutine meridional_flux_thickness(v, h, h_S, h_N, h_v, dt, G, GV, US, LB, vol
if (v(i,J,k) > 0.0) then
if (vol_CFL) then ; CFL = (v(i,J,k) * dt) * (G%dx_Cv(i,J) * G%IareaT(i,j))
else ; CFL = v(i,J,k) * dt * G%IdyT(i,j) ; endif
curv_3 = h_S(i,j,k) + h_N(i,j,k) - 2.0*h(i,j,k)
curv_3 = (h_S(i,j,k) + h_N(i,j,k)) - 2.0*h(i,j,k)
h_avg = h_N(i,j,k) + CFL * (0.5*(h_S(i,j,k) - h_N(i,j,k)) + curv_3*(CFL - 1.5))
h_marg = h_N(i,j,k) + CFL * ((h_S(i,j,k) - h_N(i,j,k)) + &
3.0*curv_3*(CFL - 1.0))
elseif (v(i,J,k) < 0.0) then
if (vol_CFL) then ; CFL = (-v(i,J,k)*dt) * (G%dx_Cv(i,J) * G%IareaT(i,j+1))
else ; CFL = -v(i,J,k) * dt * G%IdyT(i,j+1) ; endif
curv_3 = h_S(i,j+1,k) + h_N(i,j+1,k) - 2.0*h(i,j+1,k)
curv_3 = (h_S(i,j+1,k) + h_N(i,j+1,k)) - 2.0*h(i,j+1,k)
h_avg = h_S(i,j+1,k) + CFL * (0.5*(h_N(i,j+1,k)-h_S(i,j+1,k)) + curv_3*(CFL - 1.5))
h_marg = h_S(i,j+1,k) + CFL * ((h_N(i,j+1,k)-h_S(i,j+1,k)) + &
3.0*curv_3*(CFL - 1.0))
Expand Down Expand Up @@ -2601,7 +2601,7 @@ subroutine PPM_limit_pos(h_in, h_L, h_R, h_min, G, iis, iie, jis, jie)
do j=jis,jie ; do i=iis,iie
! This limiter prevents undershooting minima within the domain with
! values less than h_min.
curv = 3.0*(h_L(i,j) + h_R(i,j) - 2.0*h_in(i,j))
curv = 3.0*((h_L(i,j) + h_R(i,j)) - 2.0*h_in(i,j))
if (curv > 0.0) then ! Only minima are limited.
dh = h_R(i,j) - h_L(i,j)
if (abs(dh) < curv) then ! The parabola's minimum is within the cell.
Expand Down

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