def run_pfasst(MS,u0,t0,dt,Tend):
"""
Main driver for running the serial version of SDC, MLSDC and PFASST (virtual parallelism)
Args:
MS: block of steps (list)
u0: initial values on the finest level
t0: initial time
dt: step size (could be changed here e.g. for adaptivity)
Tend: end time
Returns:
end values on the finest level
stats object containing statistics for each step, each level and each iteration
"""
# fixme: add ring parallelization as before
# fixme: use error classes for send/recv and stage errors
# fixme: last need to be able to send even if values have not been fetched yet (ring!)
# some initializations
uend = None
num_procs = len(MS)
# initial ordering of the steps: 0,1,...,Np-1
slots = [p for p in range(num_procs)]
# initialize time variables of each step
for p in slots:
MS[p].status.dt = dt # could have different dt per step here
MS[p].status.time = t0 + sum(MS[j].status.dt for j in range(p))
MS[p].status.step = p
# determine which steps are still active (time < Tend)
active = [MS[p].status.time < Tend - np.finfo(float).eps for p in slots]
# compress slots according to active steps, i.e. remove all steps which have times above Tend
active_slots = list(itertools.compress(slots, active))
# initialize block of steps with u0
MS = restart_block(MS,active_slots,u0)
# call pre-start hook
MS[active_slots[0]].levels[0].hooks.dump_pre(MS[p].status)
# main loop: as long as at least one step is still active (time < Tend), do something
while any(active):
# loop over all active steps (in the correct order)
for p in active_slots:
# print(p,MS[p].status.stage)
MS[p] = pfasst(MS[p])
# if all active steps are done (for block-parallelization, need flag to distinguish (FIXME))
if all([MS[p].status.done for p in active_slots]):
# uend is uend of the last active step in the list
uend = MS[active_slots[-1]].levels[0].uend # FIXME: only true for non-ring-parallelization?
# determine new set of active steps and compress slots accordingly
active = [MS[p].status.time+num_procs*MS[p].status.dt < Tend - np.finfo(float).eps for p in slots]
active_slots = list(itertools.compress(slots, active))
# increment timings for now active steps
for p in active_slots:
MS[p].status.time += num_procs*MS[p].status.dt
MS[p].status.step += num_procs
# restart active steps (reset all values and pass uend to u0)
MS = restart_block(MS,active_slots,uend)
# fixme: for ring parallelization
# update first and last
# update slots
# update pred_cnt
# This is only for ring-parallelization
# indx = np.argsort([MS[p].time for p in slots])
# slots = slots[indx]
# active = [MS[p].time < Tend for p in slots]
# if all(not active[p] for p in slots):
# for p in slots:
# MS[p].time =
return uend,stats.return_stats()
def run_pfasst(MS,u0,t0,dt,Tend):
"""
Main driver for running the serial version of SDC, MLSDC and PFASST (virtual parallelism)
Args:
MS: block of steps (list)
u0: initial values on the finest level
t0: initial time
dt: step size (could be changed here e.g. for adaptivity)
Tend: end time
Returns:
end values on the finest level
stats object containing statistics for each step, each level and each iteration
"""
# fixme: use error classes for send/recv and stage errors
# some initializations
uend = None
num_procs = len(MS)
if num_procs > 1:
assert len(MS[0].levels) > 1
# initial ordering of the steps: 0,1,...,Np-1
slots = [p for p in range(num_procs)]
# initialize time variables of each step
for p in slots:
MS[p].status.dt = dt # could have different dt per step here
MS[p].status.time = t0 + sum(MS[j].status.dt for j in range(p))
MS[p].status.step = p
# determine which steps are still active (time < Tend)
active = [MS[p].status.time < Tend - np.finfo(float).eps for p in slots]
# compress slots according to active steps, i.e. remove all steps which have times above Tend
active_slots = list(itertools.compress(slots, active))
# initialize block of steps with u0
MS = restart_block(MS,active_slots,u0)
# call pre-start hook
MS[active_slots[0]].levels[0].hooks.dump_pre(MS[p].status)
# main loop: as long as at least one step is still active (time < Tend), do something
while any(active):
MS_active = []
for p in active_slots:
MS_active.append(MS[p])
MS_active = pfasst(MS_active)
for p in range(len(MS_active)):
MS[active_slots[p]] = MS_active[p]
# if all active steps are done
if all([MS[p].status.done for p in active_slots]):
# uend is uend of the last active step in the list
uend = MS[active_slots[-1]].levels[0].uend
# determine new set of active steps and compress slots accordingly
active = [MS[p].status.time+num_procs*MS[p].status.dt < Tend - np.finfo(float).eps for p in slots]
active_slots = list(itertools.compress(slots, active))
# increment timings for now active steps
for p in active_slots:
MS[p].status.time += num_procs*MS[p].status.dt
MS[p].status.step += num_procs
# restart active steps (reset all values and pass uend to u0)
MS = restart_block(MS,active_slots,uend)
return uend,stats.return_stats()
