Newer
Older
from pystencils.field import Field
from pystencils.assignment import Assignment
from pystencils.astnodes import LoopOverCoordinate, Conditional, Block, SympyAssignment
from pystencils.simp.assignment_collection import AssignmentCollection
from pystencils.gpucuda.indexing import indexing_creator_from_params
from pystencils.transformations import remove_conditionals_in_staggered_kernel
def create_kernel(assignments, target='cpu', data_type="double", iteration_slice=None, ghost_layers=None,
skip_independence_check=False,
gpu_indexing='block', gpu_indexing_params=MappingProxyType({})):
"""
Creates abstract syntax tree (AST) of kernel, using a list of update equations.
Args:
assignments: can be a single assignment, sequence of assignments or an `AssignmentCollection`
target: 'cpu', 'llvm' or 'gpu'
data_type: data type used for all untyped symbols (i.e. non-fields), can also be a dict from symbol name
to type
iteration_slice: rectangular subset to iterate over, if not specified the complete non-ghost layer \
part of the field is iterated over
ghost_layers: if left to default, the number of necessary ghost layers is determined automatically
a single integer specifies the ghost layer count at all borders, can also be a sequence of
skip_independence_check: don't check that loop iterations are independent. This is needed e.g. for
periodicity kernel, that access the field outside the iteration bounds. Use with care!
cpu_openmp: True or number of threads for OpenMP parallelization, False for no OpenMP
cpu_vectorize_info: a dictionary with keys, 'vector_instruction_set', 'assume_aligned' and 'nontemporal'
for documentation of these parameters see vectorize function. Example:
'{'instruction_set': 'avx512', 'assume_aligned': True, 'nontemporal':True}'
gpu_indexing: either 'block' or 'line' , or custom indexing class, see `AbstractIndexing`
gpu_indexing_params: dict with indexing parameters (constructor parameters of indexing class)
e.g. for 'block' one can specify '{'block_size': (20, 20, 10) }'
Returns:
abstract syntax tree (AST) object, that can either be printed as source code with `show_code` or
can be compiled with through its 'compile()' member
Example:
>>> import pystencils as ps
>>> import numpy as np
>>> s, d = ps.fields('s, d: [2D]')
>>> assignment = ps.Assignment(d[0,0], s[0, 1] + s[0, -1] + s[1, 0] + s[-1, 0])
>>> ast = ps.create_kernel(assignment, target='cpu', cpu_openmp=True)
>>> kernel = ast.compile()
>>> d_arr = np.zeros([5, 5])
>>> kernel(d=d_arr, s=np.ones([5, 5]))
>>> d_arr
array([[0., 0., 0., 0., 0.],
[0., 4., 4., 4., 0.],
[0., 4., 4., 4., 0.],
[0., 4., 4., 4., 0.],
[0., 0., 0., 0., 0.]])
if isinstance(assignments, AssignmentCollection):
if 'split_groups' in assignments.simplification_hints:
split_groups = assignments.simplification_hints['split_groups']
assignments = assignments.all_assignments
if isinstance(assignments, Assignment):
assignments = [assignments]
from pystencils.cpu import create_kernel
from pystencils.cpu import add_openmp
ast = create_kernel(assignments, type_info=data_type, split_groups=split_groups,
iteration_slice=iteration_slice, ghost_layers=ghost_layers,
skip_independence_check=skip_independence_check)
if cpu_openmp:
add_openmp(ast, num_threads=cpu_openmp)
if cpu_vectorize_info:
vectorize(ast)
elif isinstance(cpu_vectorize_info, dict):
vectorize(ast, **cpu_vectorize_info)
else:
raise ValueError("Invalid value for cpu_vectorize_info")
ast = create_kernel(assignments, type_info=data_type, split_groups=split_groups,
iteration_slice=iteration_slice, ghost_layers=ghost_layers)
ast = create_cuda_kernel(assignments, type_info=data_type,
indexing_creator=indexing_creator_from_params(gpu_indexing, gpu_indexing_params),
iteration_slice=iteration_slice, ghost_layers=ghost_layers,
skip_independence_check=skip_independence_check)
return ast
else:
raise ValueError("Unknown target %s. Has to be one of 'cpu', 'gpu' or 'llvm' " % (target,))
def create_indexed_kernel(assignments, index_fields, target='cpu', data_type="double", coordinate_names=('x', 'y', 'z'),
cpu_openmp=True, gpu_indexing='block', gpu_indexing_params=MappingProxyType({})):
Similar to :func:`create_kernel`, but here not all cells of a field are updated but only cells with
coordinates which are stored in an index field. This traversal method can e.g. be used for boundary handling.
The coordinates are stored in a separated index_field, which is a one dimensional array with struct data type.
This struct has to contain fields named 'x', 'y' and for 3D fields ('z'). These names are configurable with the
'coordinate_names' parameter. The struct can have also other fields that can be read and written in the kernel, for
index_fields: list of index fields, i.e. 1D fields with struct data type
coordinate_names: name of the coordinate fields in the struct data type
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
Example:
>>> import pystencils as ps
>>> import numpy as np
>>>
>>> # Index field stores the indices of the cell to visit together with optional values
>>> index_arr_dtype = np.dtype([('x', np.int32), ('y', np.int32), ('val', np.double)])
>>> index_arr = np.array([(1, 1, 0.1), (2, 2, 0.2), (3, 3, 0.3)], dtype=index_arr_dtype)
>>> idx_field = ps.fields(idx=index_arr)
>>>
>>> # Additional values stored in index field can be accessed in the kernel as well
>>> s, d = ps.fields('s, d: [2D]')
>>> assignment = ps.Assignment(d[0,0], 2 * s[0, 1] + 2 * s[1, 0] + idx_field('val'))
>>> ast = create_indexed_kernel(assignment, [idx_field], coordinate_names=('x', 'y'))
>>> kernel = ast.compile()
>>> d_arr = np.zeros([5, 5])
>>> kernel(s=np.ones([5, 5]), d=d_arr, idx=index_arr)
>>> d_arr
array([[0. , 0. , 0. , 0. , 0. ],
[0. , 4.1, 0. , 0. , 0. ],
[0. , 0. , 4.2, 0. , 0. ],
[0. , 0. , 0. , 4.3, 0. ],
[0. , 0. , 0. , 0. , 0. ]])
"""
if isinstance(assignments, Assignment):
assignments = [assignments]
elif isinstance(assignments, AssignmentCollection):
from pystencils.cpu import create_indexed_kernel
from pystencils.cpu import add_openmp
ast = create_indexed_kernel(assignments, index_fields=index_fields, type_info=data_type,
coordinate_names=coordinate_names)
if cpu_openmp:
add_openmp(ast, num_threads=cpu_openmp)
return ast
elif target == 'llvm':
raise NotImplementedError("Indexed kernels are not yet supported in LLVM backend")
elif target == 'gpu':
from pystencils.gpucuda import created_indexed_cuda_kernel
idx_creator = indexing_creator_from_params(gpu_indexing, gpu_indexing_params)
ast = created_indexed_cuda_kernel(assignments, index_fields, type_info=data_type,
coordinate_names=coordinate_names, indexing_creator=idx_creator)
return ast
else:
raise ValueError("Unknown target %s. Has to be either 'cpu' or 'gpu'" % (target,))
def create_staggered_kernel_from_assignments(assignments, **kwargs):
assert 'iteration_slice' not in kwargs and 'ghost_layers' not in kwargs
lhs_fields = {a.lhs.atoms(Field.Access) for a in assignments}
assert len(lhs_fields) == 1
staggered_field = lhs_fields.pop()
dim = staggered_field.spatial_dimensions
counters = [LoopOverCoordinate.get_loop_counter_symbol(i) for i in range(dim)]
conditions = [counters[i] < staggered_field.shape[i] - 1 for i in range(dim)]
guarded_assignments = []
for d in range(dim):
cond = sp.And(*[conditions[i] for i in range(dim) if d != i])
guarded_assignments.append(Conditional(cond, Block(assignments)))
def create_staggered_kernel(staggered_field, expressions, subexpressions=(), target='cpu', **kwargs):
"""Kernel that updates a staggered field.
staggered_field: field where the first index coordinate defines the location of the staggered value
can have 1 or 2 index coordinates, in case of two index coordinates at every staggered location
a vector is stored, expressions parameter has to be a sequence of sequences then
where e.g. ``f[0,0](0)`` is interpreted as value at the left cell boundary, ``f[1,0](0)`` the right cell
boundary and ``f[0,0](1)`` the southern cell boundary etc.
expressions: sequence of expressions of length dim, defining how the west, southern, (bottom) cell boundary
should be updated.
subexpressions: optional sequence of Assignments, that define subexpressions used in the main expressions
target: 'cpu' or 'gpu'
kwargs: passed directly to create_kernel, iteration slice and ghost_layers parameters are not allowed
AST, see `create_kernel`
"""
assert 'iteration_slice' not in kwargs and 'ghost_layers' not in kwargs
assert staggered_field.index_dimensions in (1, 2), 'Staggered field must have one or two index dimensions'
dim = staggered_field.spatial_dimensions
counters = [LoopOverCoordinate.get_loop_counter_symbol(i) for i in range(dim)]
conditions = [counters[i] < staggered_field.shape[i] - 1 for i in range(dim)]
assert len(expressions) == dim
if staggered_field.index_dimensions == 2:
assert all(len(sublist) == len(expressions[0]) for sublist in expressions), \
"If staggered field has two index dimensions expressions has to be a sequence of sequences of all the " \
"same length."
final_assignments = []
for d in range(dim):
cond = sp.And(*[conditions[i] for i in range(dim) if d != i])
if staggered_field.index_dimensions == 1:
assignments = [Assignment(staggered_field(d), expressions[d])]
a_coll = AssignmentCollection(assignments, list(subexpressions)).new_filtered([staggered_field(d)])
elif staggered_field.index_dimensions == 2:
assert staggered_field.has_fixed_index_shape
assignments = [Assignment(staggered_field(d, i), expr) for i, expr in enumerate(expressions[d])]
a_coll = AssignmentCollection(assignments, list(subexpressions))
a_coll = a_coll.new_filtered([staggered_field(d, i) for i in range(staggered_field.index_shape[1])])
sp_assignments = [SympyAssignment(a.lhs, a.rhs) for a in a_coll.all_assignments]
final_assignments.append(Conditional(cond, Block(sp_assignments)))
ghost_layers = [(1, 0)] * dim
cpu_vectorize_info = kwargs.get('cpu_vectorize_info', None)
if cpu_vectorize_info:
del kwargs['cpu_vectorize_info']
ast = create_kernel(final_assignments, ghost_layers=ghost_layers, target=target, **kwargs)
if target == 'cpu':
remove_conditionals_in_staggered_kernel(ast)
if cpu_vectorize_info is True:
vectorize(ast)
elif isinstance(cpu_vectorize_info, dict):
vectorize(ast, **cpu_vectorize_info)