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Add functionality to print patch statistics in ASMStarPC and friends #3875

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Add functionality to print patch statistics in ASMStarPC and friends #3875

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26 changes: 25 additions & 1 deletion firedrake/preconditioners/asm.py
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Original file line number Diff line number Diff line change
Expand Up @@ -33,7 +33,7 @@ def initialize(self, pc):
# Extract function space and mesh to obtain plex and indexing functions
V = get_function_space(dm)

# Obtain patches from user defined funtion
# Obtain patches from user defined function
ises = self.get_patches(V)
# PCASM expects at least one patch, so we define an empty one on idle processes
if len(ises) == 0:
Expand Down Expand Up @@ -103,6 +103,30 @@ def get_patches(self, V):

def view(self, pc, viewer=None):
self.asmpc.view(viewer=viewer)
self.prefix = pc.getOptionsPrefix() + self._prefix

if viewer is not None:
opts = PETSc.Options(self.prefix)
print_statistics = opts.getBool("print_patch_statistics", default=False)

if print_statistics:
from mpi4py import MPI

dm = pc.getDM()
V = get_function_space(dm)

# Obtain patches from user defined function
ises = self.get_patches(V)
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It feels slightly extravagant to completely recompute the patch indices just for the sake of this monitor, but it is true that we don't stash these anywhere convenient for us to find. Is it worth stashing them in __init__ so that we don't need to recompute them here?

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I agree it's a bit wasteful. I agree we could stash them in __init__ if the option is present. I'll make this change.

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Isn't the correct approach here to compute the statistics during __init__ if the options are present? Then just stash the statistics to save memory.

# PCASM expects at least one patch, so we define an empty one on idle processes
if len(ises) == 0:
ises = [PETSc.IS().createGeneral(numpy.empty(0, dtype=IntType), comm=PETSc.COMM_SELF)]

max_local_patch = max(is_.getSize() for is_ in ises)
min_local_patch = min(is_.getSize() for is_ in ises)
max_global_patch = pc.comm.tompi4py().allreduce(max_local_patch, op=MPI.MAX)
min_global_patch = pc.comm.tompi4py().allreduce(min_local_patch, op=MPI.MIN)

viewer.printfASCII(f"Minimum / maximum patch sizes: {min_global_patch} / {max_global_patch}\n")

def update(self, pc):
# This is required to update an inplace ILU factorization
Expand Down
2 changes: 2 additions & 0 deletions tests/regression/test_star_pc.py
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Expand Up @@ -41,6 +41,7 @@ def test_star_equivalence(problem_type, backend):

star_params = {"mat_type": "aij",
"snes_type": "ksponly",
"snes_view": None,
"ksp_type": "richardson",
"pc_type": "mg",
"pc_mg_type": "multiplicative",
Expand All @@ -50,6 +51,7 @@ def test_star_equivalence(problem_type, backend):
"mg_levels_ksp_max_it": 1,
"mg_levels_pc_type": "python",
"mg_levels_pc_python_type": "firedrake.ASMStarPC",
"mg_levels_pc_star_print_patch_statistics": None,
"mg_levels_pc_star_construct_dim": 0}

comp_params = {"mat_type": "aij",
Expand Down
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