当我在下面的代码中启用OpenMP行时，我通常不会得到正确的解决方案（所以我怀疑并行化有问题）。我一遍又一遍地看过代码，但我仍然无法找到问题所在。
!$OMP PARALLEL SHARED(w, h, u, v, hu, hv, d) &
!$OMP& SHARED(nxw, nyw) &
!$OMP& SHARED(rx, ry, rxg, ryg) &
!$OMP& SHARED(ispans, ispane, jspans, jspane, chunk) &
!$OMP& SHARED(a) &
!$OMP& PRIVATE(i, j, it) &
!$OMP& PRIVATE(ip1, im1, im2, jp1, jm1, jm2, iu1, jv1) &
!$OMP& PRIVATE(ww, hh, uu, vv, hu1, hu2, hv1, hv2, dd, df) &
!$OMP& PRIVATE(xvv, xuu, xve, xue, advx, advy) &
!$OMP& PRIVATE(c, dwdt_i, dwdt_f, dwdt, ref, coef) &
!$OMP& PRIVATE(du, dv, noflux)
ompstart = OMP_GET_WTIME()
do it = 1, itlast
!$OMP DO SCHEDULE(DYNAMIC, CHUNK)
do j = 2, nyw-1
do i = 2, nxw-1
if (d(i,j) .gt. rpmax) then
ww = w(i,j,1) - rx*(u(i,j,1) - u(i-1,j,1)) &
- ry*(v(i,j,1) - v(i,j-1,1))
if (abs(ww) .lt. eps) ww = 0.0
hh = ww + d(i,j)
if (hh .ge. gx) then
h(i,j,2) = hh
w(i,j,2) = ww
else
h(i,j,2) = 0.0
w(i,j,2) = -d(i,j)
end if
else
h(i,j,2) = 0.0
w(i,j,2) = -d(i,j)
end if
end do
end do
!$OMP END DO
!$OMP DO SCHEDULE(DYNAMIC, CHUNK)
do j = 1, nyw
do i = 1, nxw-1
hu1 = 0.25*(h(i,j,2) + h(i+1,j,2) + h(i,j,1) + h(i+1,j,1))
hu2 = 0.50*(h(i,j,2) + h(i+1,j,2))
if (hu1 .lt. gx) hu1 = 0.0
if (hu2 .lt. gx) hu2 = 0.0
hu(i,j,1) = hu1
hu(i,j,2) = hu2
end do
end do
!$OMP END DO
!$OMP DO SCHEDULE(DYNAMIC, CHUNK)
do j = 1, nyw-1
do i = 1, nxw
hv1 = 0.25*(h(i,j,2) + h(i,j+1,2) + h(i,j,1) + h(i,j+1,1))
hv2 = 0.50*(h(i,j,2) + h(i,j+1,2))
if (hv1 .lt. gx) hv1 = 0.0
if (hv2 .lt. gx) hv2 = 0.0
hv(i,j,1) = hv1
hv(i,j,2) = hv2
end do
end do
!$OMP END DO
!$OMP DO SCHEDULE(DYNAMIC, CHUNK)
do i = 1, nxw-1
ip1 = i+1
im1 = i-1
if (im1 .le. 1) im1 = 1
if (ip1 .ge. nxw-1) ip1 = nxw-1
do j = 1, nyw
noflux = 0
jp1 = j+1
jm1 = j-1
jv1 = j
if (jm1 .le. 1) jm1 = 1
if (jp1 .ge. nyw) jp1 = nyw
if (jv1 .ge. nyw-1) jv1 = nyw-1
du = 0.5*(d(i,j) + d(i+1,j))
if (d(i,j) .le. rpmax .or. du .le. rpmax) then
u(i,j,2) = 0.0
noflux = 1
else
if (h(i,j,2) .gt. gx .and. h(i+1,j,2) .gt. gx) then
dd = hu(i,j,2)
df = hu(i,j,1)
else if (h(i,j,2) .gt. gx .and. h(i+1,j,2) .le. gx &
.and. d(i+1,j) + w(i,j,2) .gt. gx) then
dd = 0.5*h(i,j,2)
df = dd
else if (h(i,j,2) .le. gx .and. h(i+1,j,2) .gt. gx &
.and. d(i,j) + w(i+1,j,2) .gt. gx) then
dd = 0.5*h(i+1,j,2)
df = dd
else
u(i,j,2) = 0.0
noflux = 1
end if
if (dd .lt. gx) then
u(i,j,2) = 0.0
noflux = 1
end if
end if
if (noflux .ne. 1) then
xvv = 0.25*(v(i,jv1,1) + v(i+1,jv1,1) + &
v(i,jm1,1) + v(i+1,jm1,1))
uu = u(i,j,1) - rxg*dd*(w(i+1,j,2) - w(i,j,2))
if (hu(i,j,1) .ge. gx .and. &
(i .gt. ispans .and. i .lt. ispane .and. &
j .gt. jspans .and. j .lt. jspane)) then
advx = 0.0
advy = 0.0
if (u(i,j,1) .lt. zero) then
if (hu(ip1,j,1) .lt. gx .or. &
h(ip1,j,2) .lt. gx) then
advx = rx*(-u(i,j,1)**2.0/hu(i,j,1))
else
advx = rx*(u(ip1,j,1)**2.0/hu(ip1,j,1) &
- u(i,j,1)**2.0/hu(i,j,1))
end if
else
if (hu(im1,j,1) .lt. gx .or. &
h(i,j,2) .lt. gx) then
advx = rx*(u(i,j,1)**2.0/hu(i,j,1))
else
advx = rx*(u(i,j,1)**2.0/hu(i,j,1) &
- u(im1,j,1)**2.0/hu(im1,j,1))
end if
end if
if (xvv .lt. zero) then
if (h(i,jp1,2) .lt. gx .or. &
h(ip1,jp1,2) .lt. gx) then
advy = ry*(-u(i,j,1)*xvv/hu(i,j,1))
else if (hu(i,jp1,1) .lt. gx) then
advy = ry*(-u(i,j,1)*xvv/hu(i,j,1))
else
xve = 0.25*(v(i,jp1,1) + v(ip1,jp1,1) &
+ v(i,j,1) + v(ip1,j,1))
advy = ry*(u(i,jp1,1)*xve/hu(i,jp1,1) &
- u(i,j,1)*xvv/hu(i,j,1))
end if
else
if (h(i,jm1,2) .lt. gx .or. &
h(ip1,jm1,2) .lt. gx) then
advy = ry*(u(i,j,1)*xvv/hu(i,j,1))
else if (hu(i,jm1,1) .lt. gx) then
advy = ry*(u(i,j,1)*xvv/hu(i,j,1))
else
jm2 = j-2
if (jm2 .le. 1) jm2 = 1
xve = 0.25*(v(i,jm1,1) + v(ip1,jm1,1) &
+ v(i,jm2,1) + v(ip1,jm2,1))
advy = ry*(u(i,j,1)*xvv/hu(i,j,1) &
- u(i,jm1,1)*xve/hu(i,jm1,1))
end if
end if
C = SQRT(GRAV*H(I,J,2))
DWDT_F = 0.08*C
DWDT_I = 0.65*C
DWDT = ABS(W(I,J,2) - W(I,J,1))/DELT
IF (DWDT .GT. DWDT_F) THEN
REF = (DWDT - DWDT_F)/(DWDT_I - DWDT_F)
A = 1.0
COEF = EXP(-A*REF)
ADVX = COEF*ADVX
ADVY = COEF*ADVY
END IF
uu = uu - advx - advy
end if
if (abs(uu) .lt. eps) uu = 0.0
if (uu .gt. 20.0*dd) uu = 20.0*dd
if (uu .lt. -20.0*dd) uu = -20.0*dd
u(i,j,2) = uu
else
u(i,j,2) = 0.0
end if
end do
end do
!$OMP END DO
!$OMP DO SCHEDULE(DYNAMIC, CHUNK)
do i = 1, nxw
ip1 = i+1
im1 = i-1
iu1 = i
if (im1 .le. 1) im1 = 1
if (ip1 .ge. nxw) ip1 = nxw
if (iu1 .ge. nxw-1) iu1 = nxw-1
do j = 1, nyw-1
noflux = 0
jp1 = j+1
jm1 = j-1
if (jm1 .le. 1) jm1 = 1
if (jp1 .ge. nyw-1) jp1 = nyw-1
dv = 0.5*(d(i,j) + d(i,j+1))
if (d(i,j) .le. rpmax .or. dv .le. rpmax) then
v(i,j,2) = 0.0
noflux = 1
else
if (h(i,j,2) .gt. gx .and. h(i,j+1,2) .gt. gx) then
dd = hv(i,j,2)
df = hv(i,j,1)
else if (h(i,j,2) .gt. gx .and. h(i,j+1,2) .le. gx &
.and. d(i,j+1) + w(i,j,2) .gt. gx) then
dd = 0.5*h(i,j,2)
df = dd
else if (h(i,j,2) .le. gx .and. h(i,j+1,2) .gt. gx &
.and. d(i,j) + w(i,j+1,2) .gt. gx) then
dd = 0.5*h(i,j+1,2)
df = dd
else
v(i,j,2) = 0.0
noflux = 1
end if
if (dd .lt. gx) then
v(i,j,2) = 0.0
noflux = 1
end if
end if
if (noflux .ne. 1) then
xuu = 0.25*(u(iu1,j,1) + u(iu1,jp1,1) + &
u(im1,j,1) + u(im1,jp1,1))
vv = v(i,j,1) - ryg*dd*(w(i,j+1,2) - w(i,j,2))
if (hv(i,j,1) .ge. gx .and. &
(i .gt. ispans .and. i .lt. ispane .and. &
j .gt. jspans .and. j .lt. jspane)) then
advx = 0.0
advy = 0.0
if (v(i,j,1) .lt. zero) then
if (hv(i,jp1,1) .lt. gx .or. &
h(i,jp1,2) .lt. gx) then
advy = ry*(-v(i,j,1)**2.0/hv(i,j,1))
else
advy = ry*(v(i,jp1,1)**2.0/hv(i,jp1,1) &
- v(i,j,1)**2.0/hv(i,j,1))
end if
else
if (hv(i,jm1,1) .lt. gx .or. &
h(i,j,2) .lt. gx) then
advy = ry*(v(i,j,1)**2.0/hv(i,j,1))
else
advy = ry*(v(i,j,1)**2.0/hv(i,j,1) &
- v(i,jm1,1)**2.0/hv(i,jm1,1))
end if
end if
if (xuu .lt. zero) then
if (h(ip1,j,2) .lt. gx .or. &
h(ip1,jp1,2) .lt. gx) then
advx = rx*(-v(i,j,1)*xuu/hv(i,j,1))
else if (hv(ip1,j,1) .lt. gx) then
advx = rx*(-v(i,j,1)*xuu/hv(i,j,1))
else
xue = 0.25*(u(ip1,j,1) + u(ip1,jp1,1) &
+ u(i,j,1) + u(i,jp1,1))
advx = rx*(v(ip1,j,1)*xue/hv(ip1,j,1) &
- v(i,j,1)*xuu/hv(i,j,1))
end if
else
if (h(im1,j,2) .lt. gx .or. &
h(im1,jp1,2) .lt. gx) then
advx = rx*(v(i,j,1)*xuu/hv(i,j,1))
else if (hv(im1,j,1) .lt. gx) then
advx = rx*(v(i,j,1)*xuu/hv(i,j,1))
else
im2 = i-2
if (im2 .le. 1) im2 = 1
xue = 0.25*(u(im1,j,1) + u(im1,jp1,1) &
+ u(im2,j,1) + u(im2,jp1,1))
advx = rx*(v(i,j,1)*xuu/hv(i,j,1) &
- v(im1,j,1)*xue/hv(im1,j,1))
end if
end if
C = SQRT(GRAV*H(I,J,2))
DWDT_F = 0.08*C
DWDT_I = 0.65*C
DWDT = ABS(W(I,J,2) - W(I,J,1))/DELT
IF (DWDT .GT. DWDT_F) THEN
REF = (DWDT - DWDT_F)/(DWDT_I - DWDT_F)
A = 1.0
COEF = EXP(-A*REF)
ADVX = COEF*ADVX
ADVY = COEF*ADVY
END IF
vv = vv - advx - advy
end if
if (abs(vv) .lt. eps) vv = 0.0
if (vv .gt. 20.0*dd) vv = 20.0*dd
if (vv .lt. -20.0*dd) vv = -20.0*dd
v(i,j,2) = vv
else
v(i,j,2) = 0.0
end if
end do
end do
!$OMP END DO
!$OMP SINGLE
call tuna_openbc
!$OMP END SINGLE
!$OMP SINGLE
call tuna_update
!$OMP END SINGLE
end do
ompend = OMP_GET_WTIME()
!$OMP END PARALLEL
上面的代码是计算部分（它是一个冗长的代码）。我确保所有循环计数器it, i, j和虚拟循环计数器ip1, im1, jp1, jm1等都设置为私有。此外，所有虚拟变量ww, uu, vv等都设置为私有。我不确定我做错了什么。我的所有变量和常量都在模块中声明，如下所示。
real, parameter :: gx = 1.0e-5
real, parameter :: eps = 1.0e-10
real, parameter :: zero = 0.0
real, parameter :: rpmax = -20.0
real, parameter :: grav = 9.807
real, dimension(:,:,:), allocatable :: w
real, dimension(:,:,:), allocatable :: h
real, dimension(:,:,:), allocatable :: u
real, dimension(:,:,:), allocatable :: v
real, dimension(:,:,:), allocatable :: hu
real, dimension(:,:,:), allocatable :: hv
real, dimension(:,:), allocatable :: d
integer :: nxw, nyw
real :: delx, dely, delt
如果您发现不对劲，请分享。
答案 0 :(得分：1)
AFAICS，您的代码暴露了两个奇怪的地方：
a声明为shared，而它看起来应该已声明为private ompstart区域之外初始化两个变量ompend和parallel。否则，所有线程都会尝试同时更新它们。所有其他变量对我来说都很好。另外，我试图检查u和v的各种索引之间的潜在依赖关系，但没有发现任何索引。因此，声明a private可能足以修复您的代码。