Allow reference profiles to be updated

gusto/core/io.py

@@ -13,14 +13,22 @@
 from pyop2.mpi import MPI
 import numpy as np
 from gusto.core.logging import logger, update_logfile_location
+from collections import namedtuple
 
-__all__ = ["pick_up_mesh", "IO"]
+__all__ = ["pick_up_mesh", "IO", "TimeData"]
 
 
 class GustoIOError(IOError):
     pass
 
 
+# A named tuple object encapsulating data about timing
+TimeData = namedtuple(
+    'TimeData',
+    ['t', 'step', 'initial_steps', 'last_ref_update_time']
+)
+
+
 def pick_up_mesh(output, mesh_name):
     """
     Picks up a checkpointed mesh. This must be the first step of any model being
@@ -531,7 +539,14 @@ def setup_dump(self, state_fields, t, pick_up=False):
 
         # dump initial fields
         if not pick_up:
-            self.dump(state_fields, t, step=1)
+            step = 1
+            last_ref_update_time = None
+            initial_steps = None
+            time_data = TimeData(
+                t=t, step=step, initial_steps=initial_steps,
+                last_ref_update_time=last_ref_update_time
+            )
+            self.dump(state_fields, time_data)
 
     def pick_up_from_checkpoint(self, state_fields):
         """
@@ -541,7 +556,10 @@ def pick_up_from_checkpoint(self, state_fields):
             state_fields (:class:`StateFields`): the model's field container.
 
         Returns:
-            float: the checkpointed model time.
+            tuple of (`time_data`, `reference_profiles`): where `time_data`
+                itself is a named tuple containing the timing data.
+                The `reference_profiles` are a list of (`field_name`, expr)
+                pairs describing the reference profile fields.
         """
 
         # -------------------------------------------------------------------- #
@@ -602,6 +620,13 @@ def pick_up_from_checkpoint(self, state_fields):
                     except AttributeError:
                         initial_steps = None
 
+                    # Try to pick up number last_ref_update_time
+                    # Not compulsory so errors allowed
+                    try:
+                        last_ref_update_time = chk.read_attribute("/", "last_ref_update_time")
+                    except AttributeError:
+                        last_ref_update_time = None
+
                     # Finally pick up time and step number
                     t = chk.read_attribute("/", "time")
                     step = chk.read_attribute("/", "step")
@@ -632,6 +657,13 @@ def pick_up_from_checkpoint(self, state_fields):
                     else:
                         initial_steps = None
 
+                    # Try to pick up last reference profile update time
+                    # Not compulsory so errors allowed
+                    if chk.has_attr("/", "last_ref_update_time"):
+                        last_ref_update_time = chk.get_attr("/", "last_ref_update_time")
+                    else:
+                        last_ref_update_time = None
+
                     # Finally pick up time
                     t = chk.get_attr("/", "time")
                     step = chk.get_attr("/", "step")
@@ -647,9 +679,14 @@ def pick_up_from_checkpoint(self, state_fields):
             if hasattr(diagnostic_field, "init_field_set"):
                 diagnostic_field.init_field_set = True
 
-        return t, reference_profiles, step, initial_steps
+        time_data = TimeData(
+            t=t, step=step, initial_steps=initial_steps,
+            last_ref_update_time=last_ref_update_time
+        )
+
+        return time_data, reference_profiles
 
-    def dump(self, state_fields, t, step, initial_steps=None):
+    def dump(self, state_fields, time_data):
         """
         Dumps all of the required model output.
 
@@ -659,12 +696,20 @@ def dump(self, state_fields, t, step, initial_steps=None):
 
         Args:
             state_fields (:class:`StateFields`): the model's field container.
-            t (float): the simulation's current time.
-            step (int): the number of time steps.
-            initial_steps (int, optional): the number of initial time steps
-                completed by a multi-level time scheme. Defaults to None.
+            time_data (namedtuple): contains information relating to the time in
+                the simulation. The tuple is structured as follows:
+                - t: current time in s
+                - step: the index of the time step
+                - initial_steps: number of initial time steps completed by a
+                  multi-level time scheme (could be None)
+                - last_ref_update_time: the last time in s that the reference
+                  profiles were updated (could be None)
         """
         output = self.output
+        t = time_data.t
+        step = time_data.step
+        initial_steps = time_data.initial_steps
+        last_ref_update_time = time_data.last_ref_update_time
 
         # Diagnostics:
         # Compute diagnostic fields
@@ -688,6 +733,8 @@ def dump(self, state_fields, t, step, initial_steps=None):
                 self.chkpt.write_attribute("/", "step", step)
                 if initial_steps is not None:
                     self.chkpt.write_attribute("/", "initial_steps", initial_steps)
+                if last_ref_update_time is not None:
+                    self.chkpt.write_attribute("/", "last_ref_update_time", last_ref_update_time)
             else:
                 with CheckpointFile(self.chkpt_path, 'w') as chk:
                     chk.save_mesh(self.domain.mesh)
@@ -697,6 +744,8 @@ def dump(self, state_fields, t, step, initial_steps=None):
                     chk.set_attr("/", "step", step)
                     if initial_steps is not None:
                         chk.set_attr("/", "initial_steps", initial_steps)
+                    if last_ref_update_time is not None:
+                        chk.set_attr("/", "last_ref_update_time", last_ref_update_time)
 
         if (next(self.dumpcount) % output.dumpfreq) == 0:
             if output.dump_nc:

gusto/solvers/linear_solvers.py

@@ -27,7 +27,8 @@
 from abc import ABCMeta, abstractmethod, abstractproperty
 
 
-__all__ = ["BoussinesqSolver", "LinearTimesteppingSolver", "CompressibleSolver", "ThermalSWSolver", "MoistConvectiveSWSolver"]
+__all__ = ["BoussinesqSolver", "LinearTimesteppingSolver", "CompressibleSolver",
+           "ThermalSWSolver", "MoistConvectiveSWSolver"]
 
 
 class TimesteppingSolver(object, metaclass=ABCMeta):
@@ -374,6 +375,20 @@ def L_tr(f):
         python_context = self.hybridized_solver.snes.ksp.pc.getPythonContext()
         attach_custom_monitor(python_context, logging_ksp_monitor_true_residual)
 
+    @timed_function("Gusto:UpdateReferenceProfiles")
+    def update_reference_profiles(self):
+        """
+        Updates the reference profiles.
+        """
+
+        with timed_region("Gusto:HybridProjectRhobar"):
+            logger.info('Compressible linear solver: rho average solve')
+            self.rho_avg_solver.solve()
+
+        with timed_region("Gusto:HybridProjectExnerbar"):
+            logger.info('Compressible linear solver: Exner average solve')
+            self.exner_avg_solver.solve()
+
     @timed_function("Gusto:LinearSolve")
     def solve(self, xrhs, dy):
         """
@@ -387,15 +402,6 @@ def solve(self, xrhs, dy):
         """
         self.xrhs.assign(xrhs)
 
-        # TODO: can we avoid computing these each time the solver is called?
-        with timed_region("Gusto:HybridProjectRhobar"):
-            logger.info('Compressible linear solver: rho average solve')
-            self.rho_avg_solver.solve()
-
-        with timed_region("Gusto:HybridProjectExnerbar"):
-            logger.info('Compressible linear solver: Exner average solve')
-            self.exner_avg_solver.solve()
-
         # Solve the hybridized system
         logger.info('Compressible linear solver: hybridized solve')
         self.hybridized_solver.solve()

gusto/timestepping/semi_implicit_quasi_newton.py

@@ -35,7 +35,8 @@ def __init__(self, equation_set, io, transport_schemes, spatial_methods,
                  diffusion_schemes=None, physics_schemes=None,
                  slow_physics_schemes=None, fast_physics_schemes=None,
                  alpha=Constant(0.5), off_centred_u=False,
-                 num_outer=2, num_inner=2, accelerator=False):
+                 num_outer=2, num_inner=2, accelerator=False,
+                 reference_update_freq=None):
 
         """
         Args:
@@ -84,13 +85,24 @@ def __init__(self, equation_set, io, transport_schemes, spatial_methods,
                 implicit forcing (pressure gradient and Coriolis) terms, and the
                 linear solve. Defaults to 2. Note that default used by the Met
                 Office's ENDGame and GungHo models is 2.
-            accelerator (bool, optional): Whether to zero non-wind implicit forcings
-                for transport terms in order to speed up solver convergence
+            accelerator (bool, optional): Whether to zero non-wind implicit
+                forcings for transport terms in order to speed up solver
+                convergence. Defaults to False.
+            reference_update_freq (float, optional): frequency with which to
+                update the reference profile with the n-th time level state
+                fields. This variable corresponds to time in seconds, and
+                setting this to zero will update the reference profiles every
+                time step. Setting it to None turns off the update, and
+                reference profiles will remain at their initial values.
+                Defaults to None.
         """
 
         self.num_outer = num_outer
         self.num_inner = num_inner
         self.alpha = alpha
+        self.accelerator = accelerator
+        self.reference_update_freq = reference_update_freq
+        self.to_update_ref_profile = False
 
         # default is to not offcentre transporting velocity but if it
         # is offcentred then use the same value as alpha
@@ -188,7 +200,6 @@ def __init__(self, equation_set, io, transport_schemes, spatial_methods,
             self.linear_solver = linear_solver
         self.forcing = Forcing(equation_set, self.alpha)
         self.bcs = equation_set.bcs
-        self.accelerator = accelerator
 
     def _apply_bcs(self):
         """
@@ -252,6 +263,24 @@ def copy_active_tracers(self, x_in, x_out):
         for name in self.tracers_to_copy:
             x_out(name).assign(x_in(name))
 
+    def update_reference_profiles(self):
+        """
+        Updates the reference profiles and if required also updates them in the
+        linear solver.
+        """
+
+        if self.reference_update_freq is not None:
+            if float(self.t) + self.reference_update_freq > self.last_ref_update_time:
+                self.equation.X_ref.assign(self.x.n(self.field_name))
+                self.last_ref_update_time = float(self.t)
+                if hasattr(self.linear_solver, 'update_reference_profiles'):
+                    self.linear_solver.update_reference_profiles()
+
+        elif self.to_update_ref_profile:
+            if hasattr(self.linear_solver, 'update_reference_profiles'):
+                self.linear_solver.update_reference_profiles()
+                self.to_update_ref_profile = False
+
     def timestep(self):
         """Defines the timestep"""
         xn = self.x.n
@@ -264,13 +293,18 @@ def timestep(self):
         xrhs_phys = self.xrhs_phys
         dy = self.dy
 
+        # Update reference profiles --------------------------------------------
+        self.update_reference_profiles()
+
+        # Slow physics ---------------------------------------------------------
         x_after_slow(self.field_name).assign(xn(self.field_name))
         if len(self.slow_physics_schemes) > 0:
             with timed_stage("Slow physics"):
                 logger.info('Semi-implicit Quasi Newton: Slow physics')
                 for _, scheme in self.slow_physics_schemes:
                     scheme.apply(x_after_slow(scheme.field_name), x_after_slow(scheme.field_name))
 
+        # Explict forcing ------------------------------------------------------
         with timed_stage("Apply forcing terms"):
             logger.info('Semi-implicit Quasi Newton: Explicit forcing')
             # Put explicit forcing into xstar
@@ -280,8 +314,10 @@ def timestep(self):
         # the correct values
         xp(self.field_name).assign(xstar(self.field_name))
 
+        # OUTER ----------------------------------------------------------------
         for outer in range(self.num_outer):
 
+            # Transport --------------------------------------------------------
             with timed_stage("Transport"):
                 self.io.log_courant(self.fields, 'transporting_velocity',
                                     message=f'transporting velocity, outer iteration {outer}')
@@ -290,6 +326,7 @@ def timestep(self):
                     # transports a field from xstar and puts result in xp
                     scheme.apply(xp(name), xstar(name))
 
+            # Fast physics -----------------------------------------------------
             x_after_fast(self.field_name).assign(xp(self.field_name))
             if len(self.fast_physics_schemes) > 0:
                 with timed_stage("Fast physics"):
@@ -302,8 +339,7 @@ def timestep(self):
 
             for inner in range(self.num_inner):
 
-                # TODO: this is where to update the reference state
-
+                # Implicit forcing ---------------------------------------------
                 with timed_stage("Apply forcing terms"):
                     logger.info(f'Semi-implicit Quasi Newton: Implicit forcing {(outer, inner)}')
                     self.forcing.apply(xp, xnp1, xrhs, "implicit")
@@ -314,6 +350,7 @@ def timestep(self):
                 xrhs -= xnp1(self.field_name)
                 xrhs += xrhs_phys
 
+                # Linear solve -------------------------------------------------
                 with timed_stage("Implicit solve"):
                     logger.info(f'Semi-implicit Quasi Newton: Mixed solve {(outer, inner)}')
                     self.linear_solver.solve(xrhs, dy)  # solves linear system and places result in dy
@@ -353,10 +390,18 @@ def run(self, t, tmax, pick_up=False):
             pick_up: (bool): specify whether to pick_up from a previous run
         """
 
-        if not pick_up:
+        if not pick_up and self.reference_update_freq is None:
             assert self.reference_profiles_initialised, \
                 'Reference profiles for must be initialised to use Semi-Implicit Timestepper'
 
+        if not pick_up and self.reference_update_freq is not None:
+            # Force reference profiles to be updated on first time step
+            self.last_ref_update_time = float(t) - float(self.dt)
+
+        elif not pick_up or (pick_up and self.reference_update_freq is None):
+            # Indicate that linear solver profile needs updating
+            self.to_update_ref_profile = True
+
         super().run(t, tmax, pick_up=pick_up)