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377 lines
16 KiB
Python
377 lines
16 KiB
Python
"""
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Class for constructing and holding the basic FDTD operations and fields
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"""
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from typing import List, Dict, Callable
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from collections import OrderedDict
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import numpy
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import jinja2
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import warnings
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import pyopencl
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import pyopencl.array
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from pyopencl.elementwise import ElementwiseKernel
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from fdfd_tools import vec
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__author__ = 'Jan Petykiewicz'
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# Create jinja2 env on module load
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jinja_env = jinja2.Environment(loader=jinja2.PackageLoader(__name__, 'kernels'))
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class Simulation(object):
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"""
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Constructs and holds the basic FDTD operations and related fields
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After constructing this object, call the (update_E, update_H, update_S) members
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to perform FDTD updates on the stored (E, H, S) fields:
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pmls = [{'axis': a, 'polarity': p} for a in 'xyz' for p in 'np']
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sim = Simulation(grid.grids, do_poynting=True, pmls=pmls)
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with open('sources.c', 'w') as f:
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f.write('{}'.format(sim.sources))
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for t in range(max_t):
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sim.update_E([]).wait()
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# Find the linear index for the center point, for Ey
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ind = numpy.ravel_multi_index(tuple(grid.shape//2), dims=grid.shape, order='C') + \
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numpy.prod(grid.shape) * 1
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# Perturb the field (i.e., add a soft current source)
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sim.E[ind] += numpy.sin(omega * t * sim.dt)
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event = sim.update_H([])
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if sim.update_S:
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event = sim.update_S([event])
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event.wait()
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with lzma.open('saved_simulation', 'wb') as f:
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dill.dump(fdfd_tools.unvec(sim.E.get(), grid.shape), f)
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Code in the form
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event2 = sim.update_H([event0, event1])
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indicates that the update_H operation should be prepared immediately, but wait for
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event0 and event1 to occur (i.e. previous operations to finish) before starting execution.
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event2 can then be used to prepare further operations to be run after update_H.
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"""
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E = None # type: pyopencl.array.Array
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H = None # type: pyopencl.array.Array
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S = None # type: pyopencl.array.Array
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eps = None # type: pyopencl.array.Array
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dt = None # type: float
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inv_dxes = None # type: List[pyopencl.array.Array]
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arg_type = None # type: numpy.float32 or numpy.float64
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context = None # type: pyopencl.Context
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queue = None # type: pyopencl.CommandQueue
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update_E = None # type: Callable[[List[pyopencl.Event]], pyopencl.Event]
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update_H = None # type: Callable[[List[pyopencl.Event]], pyopencl.Event]
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update_S = None # type: Callable[[List[pyopencl.Event]], pyopencl.Event]
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update_J = None # type: Callable[[List[pyopencl.Event]], pyopencl.Event]
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sources = None # type: Dict[str, str]
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def __init__(self,
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epsilon: List[numpy.ndarray],
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pmls: List[Dict[str, int or float]],
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bloch_boundaries: List[Dict[str, int or float]] = (),
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dxes: List[List[numpy.ndarray]] or float = None,
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dt: float = None,
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initial_fields: Dict[str, List[numpy.ndarray]] = None,
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context: pyopencl.Context = None,
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queue: pyopencl.CommandQueue = None,
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float_type: numpy.float32 or numpy.float64 = numpy.float32,
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do_poynting: bool = True,
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do_fieldsrc: bool = False):
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"""
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Initialize the simulation.
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:param epsilon: List containing [eps_r,xx, eps_r,yy, eps_r,zz], where each element is a Yee-shifted ndarray
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spanning the simulation domain. Relative epsilon is used.
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:param pmls: List of dicts with keys:
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'axis': One of 'x', 'y', 'z'.
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'direction': One of 'n', 'p'.
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'thickness': Number of layers, default 8.
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'epsilon_eff': Effective epsilon to match to. Default 1.0.
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'mu_eff': Effective mu to match to. Default 1.0.
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'ln_R_per_layer': Desired (ln(R) / thickness) value. Default -1.6.
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'm': Polynomial grading exponent. Default 3.5.
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'ma': Exponent for alpha. Default 1.
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:param bloch_boundaries: List of dicts with keys:
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'axis': One of 'x', 'y', 'z'.
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'real': Real part of bloch phase factor (i.e. real(exp(i * phase)))
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'imag': Imaginary part of bloch phase factor (i.e. imag(exp(i * phase)))
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:param dt: Time step. Default is min(dxes) * .99/sqrt(3).
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:param initial_fields: Dict with optional keys ('E', 'H', 'F', 'G') containing initial values for the
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specified fields (default is 0 everywhere). Fields have same format as epsilon.
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:param context: pyOpenCL context. If not given, pyopencl.create_some_context(False) is called.
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:param queue: pyOpenCL command queue. If not given, pyopencl.CommandQueue(context) is called.
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:param float_type: numpy.float32 or numpy.float64. Default numpy.float32.
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:param do_poynting: If true, enables calculation of the poynting vector, S.
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Poynting vector calculation adds the following computational burdens:
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* During update_H, ~6 extra additions/cell are performed in order to spatially
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average E and temporally average H. These quantities are multiplied
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(6 multiplications/cell) and then stored (6 writes/cell, cache-friendly).
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* update_S performs a discrete cross product using the precalculated products
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from update_H. This is not nice to the cache and similar to e.g. update_E
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in complexity.
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* GPU memory requirements are approximately doubled, since S and the intermediate
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products must be stored.
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"""
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if initial_fields is None:
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initial_fields = {}
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self.shape = epsilon[0].shape
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self.arg_type = float_type
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self.sources = {}
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self._create_context(context, queue)
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self._create_eps(epsilon)
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if dxes is None:
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dxes = 1.0
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if isinstance(dxes, (float, int)):
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uniform_dx = dxes
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min_dx = dxes
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else:
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uniform_dx = False
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self.inv_dxes = [self._create_field(1 / dxn) for dxn in dxes[0] + dxes[1]]
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min_dx = min(min(dxn) for dxn in dxes[0] + dxes[1])
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max_dt = min_dx * .99 / numpy.sqrt(3)
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if dt is None:
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self.dt = max_dt
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elif dt > max_dt:
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warnings.warn('Warning: unstable dt: {}'.format(dt))
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elif dt <= 0:
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raise Exception('Invalid dt: {}'.format(dt))
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else:
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self.dt = dt
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self.E = self._create_field(initial_fields.get('E', None))
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self.H = self._create_field(initial_fields.get('H', None))
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if bloch_boundaries:
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self.F = self._create_field(initial_fields.get('F', None))
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self.G = self._create_field(initial_fields.get('G', None))
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for pml in pmls:
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pml.setdefault('thickness', 8)
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pml.setdefault('epsilon_eff', 1.0)
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pml.setdefault('mu_eff', 1.0)
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pml.setdefault('ln_R_per_layer', -1.6)
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pml.setdefault('m', 3.5)
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pml.setdefault('cfs_alpha', 0)
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pml.setdefault('ma', 1)
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ctype = type_to_C(self.arg_type)
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def ptr(arg: str) -> str:
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return ctype + ' *' + arg
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base_fields = OrderedDict()
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base_fields[ptr('E')] = self.E
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base_fields[ptr('H')] = self.H
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base_fields[ctype + ' dt'] = self.dt
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if uniform_dx == False:
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inv_dx_names = ['inv_d' + eh + r for eh in 'eh' for r in 'xyz']
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for name, field in zip(inv_dx_names, self.inv_dxes):
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base_fields[ptr(name)] = field
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eps_field = OrderedDict()
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eps_field[ptr('eps')] = self.eps
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if bloch_boundaries:
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base_fields[ptr('F')] = self.F
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base_fields[ptr('G')] = self.G
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bloch_fields = OrderedDict()
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bloch_fields[ptr('E')] = self.F
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bloch_fields[ptr('H')] = self.G
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bloch_fields[ctype + ' dt'] = self.dt
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bloch_fields[ptr('F')] = self.E
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bloch_fields[ptr('G')] = self.H
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common_source = jinja_env.get_template('common.cl').render(
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ftype=ctype,
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shape=self.shape,
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)
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jinja_args = {
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'common_header': common_source,
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'pmls': pmls,
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'do_poynting': do_poynting,
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'bloch': bloch_boundaries,
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'uniform_dx': uniform_dx,
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}
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E_source = jinja_env.get_template('update_e.cl').render(**jinja_args)
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H_source = jinja_env.get_template('update_h.cl').render(**jinja_args)
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self.sources['E'] = E_source
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self.sources['H'] = H_source
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if bloch_boundaries:
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bloch_args = jinja_args.copy()
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bloch_args['do_poynting'] = False
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bloch_args['bloch'] = [{'axis': b['axis'],
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'real': b['imag'],
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'imag': b['real']}
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for b in bloch_boundaries]
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F_source = jinja_env.get_template('update_e.cl').render(**bloch_args)
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G_source = jinja_env.get_template('update_h.cl').render(**bloch_args)
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self.sources['F'] = F_source
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self.sources['G'] = G_source
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S_fields = OrderedDict()
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if do_poynting:
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S_source = jinja_env.get_template('update_s.cl').render(**jinja_args)
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self.sources['S'] = S_source
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self.oS = pyopencl.array.zeros(self.queue, self.E.shape + (2,), dtype=self.arg_type)
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self.S = pyopencl.array.zeros_like(self.E)
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S_fields[ptr('oS')] = self.oS
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S_fields[ptr('S')] = self.S
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J_fields = OrderedDict()
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if do_fieldsrc:
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J_source = jinja_env.get_template('update_j.cl').render(**jinja_args)
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self.sources['J'] = J_source
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self.Ji = pyopencl.array.zeros_like(self.E)
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self.Jr = pyopencl.array.zeros_like(self.E)
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J_fields[ptr('Jr')] = self.Jr
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J_fields[ptr('Ji')] = self.Ji
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'''
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PML
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'''
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pml_e_fields, pml_h_fields = self._create_pmls(pmls)
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if bloch_boundaries:
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pml_f_fields, pml_g_fields = self._create_pmls(pmls)
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'''
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Create operations
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'''
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self.update_E = self._create_operation(E_source, (base_fields, eps_field, pml_e_fields))
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self.update_H = self._create_operation(H_source, (base_fields, pml_h_fields, S_fields))
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if do_poynting:
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self.update_S = self._create_operation(S_source, (base_fields, S_fields))
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if bloch_boundaries:
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self.update_F = self._create_operation(F_source, (bloch_fields, eps_field, pml_f_fields))
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self.update_G = self._create_operation(G_source, (bloch_fields, pml_g_fields))
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if do_fieldsrc:
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args = OrderedDict()
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[args.update(d) for d in (base_fields, J_fields)]
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var_args = [ctype + ' ' + v for v in 'cs'] + ['uint ' + r + m for r in 'xyz' for m in ('min', 'max')]
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update = ElementwiseKernel(self.context, operation=J_source,
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arguments=', '.join(list(args.keys()) + var_args))
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self.update_J = lambda e, *a: update(*args.values(), *a, wait_for=e)
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def _create_pmls(self, pmls):
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ctype = type_to_C(self.arg_type)
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def ptr(arg: str) -> str:
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return ctype + ' *' + arg
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pml_e_fields = OrderedDict()
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pml_h_fields = OrderedDict()
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for pml in pmls:
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a = 'xyz'.find(pml['axis'])
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sigma_max = -pml['ln_R_per_layer'] / 2 * (pml['m'] + 1)
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kappa_max = numpy.sqrt(pml['mu_eff'] * pml['epsilon_eff'])
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alpha_max = pml['cfs_alpha']
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def par(x):
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scaling = (x / pml['thickness']) ** pml['m']
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sigma = scaling * sigma_max
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kappa = 1 + scaling * (kappa_max - 1)
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alpha = ((1 - x / pml['thickness']) ** pml['ma']) * alpha_max
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p0 = numpy.exp(-(sigma / kappa + alpha) * self.dt)
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p1 = sigma / (sigma + kappa * alpha) * (p0 - 1)
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p2 = 1 / kappa
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return p0, p1, p2
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xe, xh = (numpy.arange(1, pml['thickness'] + 1, dtype=self.arg_type)[::-1] for _ in range(2))
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if pml['polarity'] == 'p':
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xe -= 0.5
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elif pml['polarity'] == 'n':
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xh -= 0.5
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pml_p_names = [['p' + pml['axis'] + i + eh + pml['polarity'] for i in '012'] for eh in 'eh']
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for name_e, name_h, pe, ph in zip(pml_p_names[0], pml_p_names[1], par(xe), par(xh)):
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pml_e_fields[ptr(name_e)] = pyopencl.array.to_device(self.queue, pe)
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pml_h_fields[ptr(name_h)] = pyopencl.array.to_device(self.queue, ph)
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uv = 'xyz'.replace(pml['axis'], '')
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psi_base = 'Psi_' + pml['axis'] + pml['polarity'] + '_'
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psi_names = [[psi_base + eh + c for c in uv] for eh in 'EH']
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psi_shape = list(self.shape)
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psi_shape[a] = pml['thickness']
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for ne, nh in zip(*psi_names):
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pml_e_fields[ptr(ne)] = pyopencl.array.zeros(self.queue, tuple(psi_shape), dtype=self.arg_type)
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pml_h_fields[ptr(nh)] = pyopencl.array.zeros(self.queue, tuple(psi_shape), dtype=self.arg_type)
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return pml_e_fields, pml_h_fields
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def _create_operation(self, source, args_fields):
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args = OrderedDict()
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[args.update(d) for d in args_fields]
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update = ElementwiseKernel(self.context, operation=source,
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arguments=', '.join(args.keys()))
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return lambda e: update(*args.values(), wait_for=e)
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def _create_context(self, context: pyopencl.Context = None,
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queue: pyopencl.CommandQueue = None):
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if context is None:
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self.context = pyopencl.create_some_context()
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else:
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self.context = context
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if queue is None:
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self.queue = pyopencl.CommandQueue(self.context)
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else:
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self.queue = queue
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def _create_eps(self, epsilon: List[numpy.ndarray]):
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if len(epsilon) != 3:
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raise Exception('Epsilon must be a list with length of 3')
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if not all((e.shape == epsilon[0].shape for e in epsilon[1:])):
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raise Exception('All epsilon grids must have the same shape. Shapes are {}', [e.shape for e in epsilon])
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if not epsilon[0].shape == self.shape:
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raise Exception('Epsilon shape mismatch. Expected {}, got {}'.format(self.shape, epsilon[0].shape))
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self.eps = pyopencl.array.to_device(self.queue, vec(epsilon).astype(self.arg_type))
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def _create_field(self, initial_value: List[numpy.ndarray] = None):
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if initial_value is None:
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return pyopencl.array.zeros_like(self.eps)
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else:
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if len(initial_value) != 3:
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Exception('Initial field value must be a list of length 3')
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if not all((f.shape == self.shape for f in initial_value)):
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Exception('Initial field list elements must have same shape as epsilon elements')
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return pyopencl.array.to_device(self.queue, vec(initial_value).astype(self.arg_type))
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def type_to_C(float_type) -> str:
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"""
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Returns a string corresponding to the C equivalent of a numpy type.
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Only works for float16, float32, float64.
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:param float_type: e.g. numpy.float32
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:return: string containing the corresponding C type (eg. 'double')
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"""
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if float_type == numpy.float16:
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arg_type = 'half'
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elif float_type == numpy.float32:
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arg_type = 'float'
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elif float_type == numpy.float64:
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arg_type = 'double'
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else:
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raise Exception('Unsupported type')
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return arg_type
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