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tea_solve.f90
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tea_solve.f90
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!Crown Copyright 2014 AWE.
!
! This file is part of TeaLeaf.
!
! TeaLeaf is free software: you can redistribute it and/or modify it under
! the terms of the GNU General Public License as published by the
! Free Software Foundation, either version 3 of the License, or (at your option)
! any later version.
!
! TeaLeaf is distributed in the hope that it will be useful, but
! WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
! FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
! details.
!
! You should have received a copy of the GNU General Public License along with
! TeaLeaf. If not, see http://www.gnu.org/licenses/.
!> @brief Driver for the heat conduction kernel
!> @author David Beckingsale, Wayne Gaudin
!> @details Invokes the user specified kernel for the heat conduction
MODULE tea_leaf_module
USE report_module
USE data_module
USE tea_leaf_common_module
USE tea_leaf_cg_module
USE tea_leaf_cheby_module
USE tea_leaf_ppcg_module
USE tea_leaf_jacobi_module
USE update_halo_module
IMPLICIT NONE
CONTAINS
SUBROUTINE tea_leaf()
IMPLICIT NONE
!$ INTEGER :: OMP_GET_THREAD_NUM
INTEGER :: n
REAL(KIND=8) :: old_error,error,exact_error,initial_residual
INTEGER :: fields(NUM_FIELDS)
REAL(KIND=8) :: timer,halo_time,solve_time,init_time,reset_time,dot_product_time
! For CG solver
REAL(KIND=8) :: rro, pw, rrn, alpha, beta
! For chebyshev solver
REAL(KIND=8), DIMENSION(max_iters) :: cg_alphas, cg_betas
REAL(KIND=8), DIMENSION(max_iters) :: ch_alphas, ch_betas
REAL(KIND=8),SAVE :: eigmin, eigmax, theta, cn
INTEGER :: est_itc, cheby_calc_steps, max_cheby_iters, info, ppcg_inner_iters
LOGICAL :: ch_switch_check
LOGICAL, SAVE :: first=.TRUE.
INTEGER :: cg_calc_steps
REAL(KIND=8) :: cg_time, ch_time, total_solve_time, ch_per_it, cg_per_it, iteration_time
cg_time = 0.0_8
ch_time = 0.0_8
cg_calc_steps = 0
ppcg_inner_iters = 0
ch_switch_check = .false.
total_solve_time = 0.0_8
init_time = 0.0_8
halo_time = 0.0_8
solve_time = 0.0_8
IF (coefficient .NE. RECIP_CONDUCTIVITY .AND. coefficient .NE. conductivity) THEN
CALL report_error('tea_leaf', 'unknown coefficient option')
ENDIF
tl_ppcg_active = .false. ! disable ppcg until we have the eigenvalue estimates
cheby_calc_steps = 0
cg_calc_steps = 0
total_solve_time = timer()
! INIT
IF (profiler_on) init_time=timer()
fields=0
fields(FIELD_ENERGY1) = 1
fields(FIELD_DENSITY) = 1
IF (profiler_on) halo_time=timer()
CALL update_halo(fields,chunk%halo_exchange_depth)
IF (profiler_on) init_time = init_time + (timer()-halo_time)
CALL tea_leaf_init_common()
fields=0
fields(FIELD_U) = 1
IF (profiler_on) halo_time=timer()
CALL update_halo( fields,1)
IF (profiler_on) init_time = init_time + (timer()-halo_time)
CALL tea_leaf_calc_residual()
CALL tea_leaf_calc_2norm( 1, initial_residual)
IF (profiler_on) dot_product_time=timer()
CALL tea_allsum(initial_residual)
IF (profiler_on) init_time = init_time + (timer()-dot_product_time)
old_error = initial_residual
initial_residual=SQRT(abs(initial_residual))
IF (parallel%boss.AND.verbose_on) THEN
!$ IF (OMP_GET_THREAD_NUM().EQ.0) THEN
WRITE(g_out,*)"Initial residual ",initial_residual
!$ ENDIF
ENDIF
IF (tl_use_cg .OR. tl_use_chebyshev .OR. tl_use_ppcg) THEN
! All 3 of these solvers use the CG kernels
CALL tea_leaf_cg_init(rro)
! and globally sum rro
IF (profiler_on) dot_product_time=timer()
CALL tea_allsum(rro)
IF (profiler_on) init_time = init_time + (timer()-dot_product_time)
! need to update p when using CG due to matrix/vector multiplication
fields=0
fields(FIELD_U) = 1
fields(FIELD_P) = 1
IF (profiler_on) halo_time=timer()
CALL update_halo(fields,1)
IF (profiler_on) init_time=init_time+(timer()-halo_time)
fields=0
fields(FIELD_P) = 1
ELSEIF (tl_use_jacobi) THEN
fields=0
fields(FIELD_U) = 1
ENDIF
IF (profiler_on) profiler%tea_init = profiler%tea_init + (timer() - init_time)
IF (profiler_on) solve_time = timer()
DO n=1,max_iters
iteration_time = timer()
!===================================================================================
! Switch for the number of CG iterations for Chebyshev and PPCG.
!===================================================================================
IF (ch_switch_check .EQV. .FALSE.) THEN
IF ((cheby_calc_steps .GT. 0)) THEN
! already started or already have good guesses for eigenvalues
ch_switch_check = .TRUE.
ELSE IF ((first .EQV. .FALSE.) .AND. tl_use_ppcg .AND. n .GT. 1) THEN
! If using PPCG, it can start almost immediately
ch_switch_check = .TRUE.
ELSE IF ((ABS(old_error) .LE. tl_ch_cg_epslim) .AND. (n .GE. tl_ch_cg_presteps)) THEN
! Error is less than set limit, and enough steps have passed to get a good eigenvalue guess
ch_switch_check = .TRUE.
ELSE
! keep doing CG (or jacobi)
ch_switch_check = .FALSE.
ENDIF
ENDIF
!===================================================================================
! If we use Chebyshev or PPCG we compute eigenvalue estimates
!===================================================================================
IF ((tl_use_chebyshev .OR. tl_use_ppcg) .AND. ch_switch_check) THEN
! on the first chebyshev steps, find the eigenvalues, coefficients,
! and expected number of iterations
IF (cheby_calc_steps .EQ. 0) THEN
! maximum number of iterations in chebyshev solver
max_cheby_iters = max_iters - n + 2
IF (first) THEN
! calculate eigenvalues
CALL tea_calc_eigenvalues(cg_alphas, cg_betas, eigmin, eigmax, &
max_iters, n-1, info)
first=.FALSE.
IF (info .NE. 0) CALL report_error('tea_leaf', 'Error in calculating eigenvalues')
eigmin = eigmin * 0.95_8
eigmax = eigmax * 1.05_8
ENDIF
IF (tl_use_chebyshev) THEN
! calculate chebyshev coefficients
CALL tea_calc_ch_coefs(ch_alphas, ch_betas, eigmin, eigmax, &
theta, max_cheby_iters)
! don't need to update p any more
fields = 0
fields(FIELD_U) = 1
ELSE IF (tl_use_ppcg) THEN
! currently also calculate chebyshev coefficients
CALL tea_calc_ls_coefs(ch_alphas, ch_betas, eigmin, eigmax, &
theta, tl_ppcg_inner_steps)
tl_ppcg_active=.true.
ENDIF
cn = eigmax/eigmin
IF (parallel%boss) THEN
!$ IF (OMP_GET_THREAD_NUM().EQ.0) THEN
100 FORMAT("Eigen min",e14.6," Eigen max",e14.6," Condition number",f14.6," Error",e14.6)
WRITE(g_out,'(a,i3,a,e15.7)') "Switching after ",n," CG its, error ",rro
WRITE(g_out, 100) eigmin,eigmax,cn,old_error
WRITE(0,'(a,i3,a,e15.7)') "Switching after ",n," CG its, error ",rro
WRITE(0, 100) eigmin,eigmax,cn,old_error
!$ ENDIF
ENDIF
!===================================================================================
! Reinitialise CG with PPCG applied
!===================================================================================
! Step 1: we reinitialise z if we precondition or else we just use r
CALL tea_leaf_ppcg_init(ppcg_inner_iters, ch_alphas, ch_betas, theta, solve_time, 2, rro)
! Step 2: compute a new z from r or previous z
CALL tea_leaf_run_ppcg_inner_steps(ch_alphas, ch_betas, theta, &
tl_ppcg_inner_steps, solve_time)
ppcg_inner_iters = ppcg_inner_iters + tl_ppcg_inner_steps
! Step 3: Recompute p after polynomial acceleration
CALL tea_leaf_ppcg_init(ppcg_inner_iters, ch_alphas, ch_betas, theta, solve_time, 3, rro)
! and globally sum rro
IF (profiler_on) dot_product_time=timer()
CALL tea_allsum(rro)
IF (profiler_on) init_time = init_time + (timer()-dot_product_time)
! need to update p when using CG due to matrix/vector multiplication
fields=0
fields(FIELD_P) = 1
IF (profiler_on) halo_time=timer()
CALL update_halo(fields,1)
IF (profiler_on) init_time=init_time+(timer()-halo_time)
ENDIF
!===================================================================================
! Chebyshev Iteration
!===================================================================================
IF (tl_use_chebyshev) THEN
IF (cheby_calc_steps .EQ. 0) THEN
CALL tea_leaf_cheby_first_step(ch_alphas, ch_betas, fields, &
old_error, theta, cn, max_cheby_iters, est_itc, solve_time)
cheby_calc_steps = 1
ELSE
CALL tea_leaf_cheby_iterate(ch_alphas, ch_betas, max_cheby_iters, cheby_calc_steps)
! after estimated number of iterations has passed, calc resid.
! Leaving 10 iterations between each global reduction won't affect
! total time spent much if at all (number of steps spent in
! chebyshev is typically O(300+)) but will greatly reduce global
! synchronisations needed
IF ((n .GE. est_itc) .AND. (MOD(n, 10) .eq. 0)) THEN
CALL tea_leaf_calc_2norm(1, error)
IF (profiler_on) dot_product_time=timer()
CALL tea_allsum(error)
IF (profiler_on) solve_time = solve_time + (timer()-dot_product_time)
ENDIF
ENDIF
!===================================================================================
! PPCG iteration,
! First one needs an estimate of the eigenvalues from CG.
! We are essentially doing PPFCG(1) here where the F denotes that CG is flexible.
! This accounts for rounding error arising from the polynomial preconditioning
!===================================================================================
ELSE IF (tl_use_ppcg) THEN
! w = Ap
! pw = p.w
CALL tea_leaf_cg_calc_w(pw)
! Now need to store r
CALL tea_leaf_ppcg_store_r()
! Now compute r.z for alpha
CALL tea_leaf_ppcg_calc_zrnorm(rro)
IF (profiler_on) dot_product_time=timer()
CALL tea_allsum2(pw, rro)
IF (profiler_on) solve_time = solve_time + (timer()-dot_product_time)
! alpha = z.r / (pw)
alpha = rro/pw
CALL tea_leaf_cg_calc_ur(alpha, rrn)
! not using rrn, so don't do a tea_allsum
CALL tea_leaf_run_ppcg_inner_steps(ch_alphas, ch_betas, theta, &
tl_ppcg_inner_steps, solve_time)
ppcg_inner_iters = ppcg_inner_iters + tl_ppcg_inner_steps
! We use flexible CG, FCG(1) to account for roundoff issues in the PP
CALL tea_leaf_ppcg_calc_rrn(rrn)
IF (profiler_on) dot_product_time=timer()
CALL tea_allsum(rrn)
IF (profiler_on) solve_time = solve_time + (timer()-dot_product_time)
! beta = (r.z)_{k+1} / (r.z)_{k}
beta = rrn/rro
CALL tea_leaf_cg_calc_p(beta)
error = rrn
rro = rrn
ENDIF
cheby_calc_steps = cheby_calc_steps + 1
!===================================================================================
! Either: - CG iteration
! - Or if we choose Chebyshev or PPCG we need
! a few CG iterations to get an estimate of the eigenvalues.
!===================================================================================
ELSEIF (tl_use_cg .OR. tl_use_chebyshev .OR. tl_use_ppcg) THEN
fields(FIELD_P) = 1
cg_calc_steps = cg_calc_steps + 1
! w = Ap
! pw = p.w
CALL tea_leaf_cg_calc_w(pw)
IF (profiler_on) dot_product_time=timer()
CALL tea_allsum(pw)
IF (profiler_on) solve_time = solve_time + (timer()-dot_product_time)