From 19803f9d13727c0469f0698714e7c2c3093f537c Mon Sep 17 00:00:00 2001
From: "[6~" <inform@tiker.net>
Date: Fri, 8 May 2020 01:53:46 -0500
Subject: [PATCH 1/4] Add executing (but not yet working) cartoon DG solver

---
 examples/simple-dg.py | 509 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 509 insertions(+)
 create mode 100644 examples/simple-dg.py

diff --git a/examples/simple-dg.py b/examples/simple-dg.py
new file mode 100644
index 00000000..dc780f26
--- /dev/null
+++ b/examples/simple-dg.py
@@ -0,0 +1,509 @@
+from __future__ import division, print_function
+
+__copyright__ = "Copyright (C) 2020 Andreas Kloeckner"
+
+__license__ = """
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
+"""
+
+
+import numpy as np
+import pyopencl as cl
+import pyopencl.array as cla  # noqa
+import pyopencl.clmath as clmath
+from pytools import memoize_method, memoize_in
+from pytools.obj_array import (
+        join_fields, make_obj_array,
+        with_object_array_or_scalar,
+        is_obj_array)
+import loopy as lp
+from meshmode.mesh import BTAG_ALL  # noqa
+
+
+# Features lost vs. https://github.com/inducer/grudge:
+# - dimension independence / differential geometry
+# - overintegration
+# - operator fusion
+# - distributed-memory
+
+
+def with_queue(queue, ary):
+    return with_object_array_or_scalar(
+            lambda x: x.with_queue(queue), ary)
+
+
+def without_queue(ary):
+    return with_queue(None, ary)
+
+
+# {{{ discretization
+
+def parametrization_derivative(queue, discr):
+    result = np.zeros((discr.ambient_dim, discr.dim), dtype=object)
+    for iambient in range(discr.ambient_dim):
+        for idim in range(discr.dim):
+            result[iambient, idim] = discr.num_reference_derivative(
+                    queue, (idim,), discr.nodes()[iambient])
+
+    return result
+
+
+class DGDiscretization:
+    def __init__(self, cl_ctx, mesh, order):
+        self.order = order
+
+        from meshmode.discretization import Discretization
+        from meshmode.discretization.poly_element import \
+                PolynomialWarpAndBlendGroupFactory
+        self.group_factory = PolynomialWarpAndBlendGroupFactory(order=order)
+        self.volume_discr = Discretization(cl_ctx, mesh, self.group_factory)
+
+        assert self.volume_discr.dim == 2
+
+    @property
+    def cl_context(self):
+        return self.volume_discr.cl_context
+
+    @property
+    def dim(self):
+        return self.volume_discr.dim
+
+    # {{{ discretizations/connections
+
+    @memoize_method
+    def boundary_connection(self, boundary_tag):
+        from meshmode.discretization.connection import make_face_restriction
+        return make_face_restriction(
+                        self.volume_discr,
+                        self.group_factory,
+                        boundary_tag=boundary_tag)
+
+    @memoize_method
+    def interior_faces_connection(self):
+        from meshmode.discretization.connection import (
+                make_face_restriction, FACE_RESTR_INTERIOR)
+        return make_face_restriction(
+                        self.volume_discr,
+                        self.group_factory,
+                        FACE_RESTR_INTERIOR,
+                        per_face_groups=False)
+
+    @memoize_method
+    def opposite_face_connection(self):
+        from meshmode.discretization.connection import \
+                make_opposite_face_connection
+
+        return make_opposite_face_connection(self.interior_faces_connection())
+
+    @memoize_method
+    def all_faces_connection(self):
+        from meshmode.discretization.connection import (
+                make_face_restriction, FACE_RESTR_ALL)
+        return make_face_restriction(
+                        self.volume_discr,
+                        self.group_factory,
+                        FACE_RESTR_ALL,
+                        per_face_groups=False)
+
+    @memoize_method
+    def get_to_all_face_embedding(self, where):
+        from meshmode.discretization.connection import \
+                make_face_to_all_faces_embedding
+
+        faces_conn = self.get_connection("vol", where)
+        return make_face_to_all_faces_embedding(
+                faces_conn, self.get_discr("all_faces"))
+
+    def get_connection(self, src, tgt):
+        src_tgt = (src, tgt)
+
+        if src_tgt == ("vol", "int_faces"):
+            return self.interior_faces_connection()
+        elif src_tgt == ("vol", "all_faces"):
+            return self.all_faces_connection()
+        elif src_tgt == ("int_faces", "all_faces"):
+            return self.get_to_all_face_embedding(src)
+        else:
+            raise ValueError(f"locations '{src}'->'{tgt}' not understood")
+
+    def interp(self, src, tgt, vec):
+        if is_obj_array(vec):
+            return with_object_array_or_scalar(
+                    lambda el: self.interp(src, tgt, el), vec)
+
+        return self.get_connection(src, tgt)(vec.queue, vec)
+
+    def get_discr(self, where):
+        if where == "vol":
+            return self.volume_discr
+        elif where == "all_faces":
+            return self.all_faces_connection().to_discr
+        elif where == "int_faces":
+            return self.interior_faces_connection().to_discr
+        else:
+            raise ValueError(f"location '{where}' not understood")
+
+    # }}}
+
+    @memoize_method
+    def parametrization_derivative(self):
+        with cl.CommandQueue(self.cl_context) as queue:
+            return without_queue(
+                    parametrization_derivative(queue, self.volume_discr))
+
+    @memoize_method
+    def vol_jacobian(self):
+        with cl.CommandQueue(self.cl_context) as queue:
+            [a, b], [c, d] = with_queue(queue, self.parametrization_derivative())
+            return (a*d-b*c).with_queue(None)
+
+    @memoize_method
+    def inverse_parametrization_derivative(self):
+        with cl.CommandQueue(self.cl_context) as queue:
+            [a, b], [c, d] = with_queue(queue, self.parametrization_derivative())
+
+            result = np.zeros((2, 2), dtype=object)
+            det = a*d-b*c
+            result[0, 0] = d/det
+            result[0, 1] = -b/det
+            result[1, 0] = -c/det
+            result[1, 1] = a/det
+
+            return without_queue(result)
+
+    def zeros(self, queue):
+        return self.volume_discr.zeros(queue)
+
+    def grad(self, vec):
+        ipder = self.inverse_parametrization_derivative()
+
+        queue = vec.queue
+        dref = [
+                self.volume_discr.num_reference_derivative(
+                    queue, (idim,), vec).with_queue(queue)
+                for idim in range(self.volume_discr.dim)]
+
+        return make_obj_array([
+            sum(dref_i*ipder_i for dref_i, ipder_i in zip(dref, ipder[iambient]))
+            for iambient in range(self.volume_discr.ambient_dim)])
+
+    def div(self, vecs):
+        return sum(
+                self.grad(vec_i)[i] for i, vec_i in enumerate(vecs))
+
+    @memoize_method
+    def normal(self, where):
+        bdry_discr = self.get_discr(where)
+
+        with cl.CommandQueue(self.cl_context) as queue:
+            ((a,), (b,)) = with_queue(
+                    queue, parametrization_derivative(queue, bdry_discr))
+
+            return without_queue(join_fields(b, -a))
+
+    @memoize_method
+    def face_jacobian(self, where):
+        bdry_discr = self.get_discr(where)
+
+        with cl.CommandQueue(self.cl_context) as queue:
+            ((a,), (b,)) = with_queue(queue,
+                    parametrization_derivative(queue, bdry_discr))
+
+            return ((a**2 + b**2)**0.5).with_queue(None)
+
+    @memoize_method
+    def get_inverse_mass_matrix(self, grp, dtype):
+        import modepy as mp
+        matrix = mp.inverse_mass_matrix(
+                grp.basis(),
+                grp.unit_nodes)
+
+        with cl.CommandQueue(self.cl_context) as queue:
+            return (cla.to_device(queue, matrix)
+                    .with_queue(None))
+
+    def inverse_mass(self, vec):
+        if is_obj_array(vec):
+            return with_object_array_or_scalar(
+                    lambda el: self.face_mass(el), vec)
+
+        @memoize_in(self, "elwise_linear_knl")
+        def knl():
+            knl = lp.make_kernel(
+                """{[k,i,j]:
+                    0<=k<nelements and
+                    0<=i<ndiscr_nodes_out and
+                    0<=j<ndiscr_nodes_in}""",
+                "result[k,i] = sum(j, mat[i, j] * vec[k, j])",
+                default_offset=lp.auto, name="diff")
+
+            knl = lp.split_iname(knl, "i", 16, inner_tag="l.0")
+            return lp.tag_inames(knl, dict(k="g.0"))
+
+        discr = self.volume_discr
+
+        result = discr.empty(queue=self.queue, dtype=vec.dtype)
+
+        for grp in discr.groups:
+            matrix = self.get_inverse_mass_matrix(grp, vec.dtype)
+
+            knl()(self.queue, mat=matrix, result=grp.view(result),
+                    vec=grp.view(vec))
+
+        return result/self.vol_jacobian()
+
+    @memoize_method
+    def get_local_face_mass_matrix(self, afgrp, volgrp, dtype):
+        nfaces = volgrp.mesh_el_group.nfaces
+        assert afgrp.nelements == nfaces * volgrp.nelements
+
+        matrix = np.empty(
+                (volgrp.nunit_nodes,
+                    nfaces,
+                    afgrp.nunit_nodes),
+                dtype=dtype)
+
+        from modepy.tools import UNIT_VERTICES
+        import modepy as mp
+        for iface, fvi in enumerate(
+                volgrp.mesh_el_group.face_vertex_indices()):
+            face_vertices = UNIT_VERTICES[volgrp.dim][np.array(fvi)].T
+            matrix[:, iface, :] = mp.nodal_face_mass_matrix(
+                    volgrp.basis(), volgrp.unit_nodes, afgrp.unit_nodes,
+                    volgrp.order,
+                    face_vertices)
+
+        with cl.CommandQueue(self.cl_context) as queue:
+            return (cla.to_device(queue, matrix)
+                    .with_queue(None))
+
+    def face_mass(self, vec):
+        if is_obj_array(vec):
+            return with_object_array_or_scalar(
+                    lambda el: self.face_mass(el), vec)
+
+        @memoize_in(self, "face_mass_knl")
+        def knl():
+            knl = lp.make_kernel(
+                """{[k,i,f,j]:
+                    0<=k<nelements and
+                    0<=f<nfaces and
+                    0<=i<nvol_nodes and
+                    0<=j<nface_nodes}""",
+                "result[k,i] = sum(f, sum(j, mat[i, f, j] * vec[f, k, j]))",
+                default_offset=lp.auto, name="face_mass")
+
+            knl = lp.split_iname(knl, "i", 16, inner_tag="l.0")
+            return lp.tag_inames(knl, dict(k="g.0"))
+
+        all_faces_conn = self.get_connection("vol", "all_faces")
+        all_faces_discr = all_faces_conn.to_discr
+        vol_discr = all_faces_conn.from_discr
+
+        result = vol_discr.empty(queue=vec.queue, dtype=vec.dtype)
+
+        assert len(all_faces_discr.groups) == len(vol_discr.groups)
+
+        for afgrp, volgrp in zip(all_faces_discr.groups, vol_discr.groups):
+            nfaces = volgrp.mesh_el_group.nfaces
+
+            matrix = self.get_local_face_mass_matrix(afgrp, volgrp, vec.dtype)
+
+            input_view = afgrp.view(vec).reshape(
+                    nfaces, volgrp.nelements, afgrp.nunit_nodes)
+            knl()(vec.queue, mat=matrix, result=volgrp.view(result),
+                    vec=input_view)
+
+        return result*self.face_jacobian("all_faces")
+
+# }}}
+
+
+# {{{ trace pair
+
+class TracePair:
+    def __init__(self, where, interior, exterior):
+        self.where = where
+        self.interior = interior
+        self.exterior = exterior
+
+    def __getitem__(self, index):
+        return TracePair(
+                self.where,
+                self.exterior[index],
+                self.interior[index])
+
+    def __len__(self):
+        assert len(self.exterior) == len(self.interior)
+        return len(self.exterior)
+
+    @property
+    def int(self):
+        return self.interior
+
+    @property
+    def ext(self):
+        return self.exterior
+
+    @property
+    def avg(self):
+        return 0.5*(self.int + self.ext)
+
+
+def interior_trace_pair(discr, vec):
+    i = discr.interp("vol", "int_faces", vec)
+    e = with_object_array_or_scalar(
+            lambda el: discr.opposite_face_connection()(el.queue, el),
+            i)
+    return TracePair("int_faces", i, e)
+
+# }}}
+
+
+# {{{ wave equation bits
+
+def wave_flux(discr, c, w_tpair):
+    u = w_tpair[0]
+    v = w_tpair[1:]
+
+    normal = with_queue(u.int.queue, discr.normal(w_tpair.where))
+
+    flux_weak = join_fields(
+            np.dot(v.avg, normal),
+            normal[0] * u.avg,
+            normal[1] * u.avg)
+
+    # upwind
+    v_jump = np.dot(normal, v.int-v.ext)
+    flux_weak -= join_fields(
+            0.5*(u.int-u.ext),
+            0.5*normal[0]*v_jump,
+            0.5*normal[1]*v_jump,
+            )
+
+    flux_strong = join_fields(
+            np.dot(v.int, normal),
+            u.int * normal[0],
+            u.int * normal[1],
+            ) - flux_weak
+
+    return discr.interp(w_tpair.where, "all_faces", c*flux_strong)
+
+
+def wave_operator(discr, c, w):
+    u = w[0]
+    v = w[1:]
+
+    # dir_u = discr.interp("vol", BTAG_ALL, u)
+    # dir_v = discr.interp("vol", BTAG_ALL, v)
+    # dir_bc = join_fields(-dir_u, dir_v)
+
+    result = (
+            - join_fields(
+                -c*discr.div(v),
+                -c*discr.grad(u)
+                )
+             +  # noqa: W504
+             discr.inverse_mass(
+                 discr.face_mass(
+                     wave_flux(discr, c=c, w_tpair=interior_trace_pair(discr, w))
+                     #+ flux(sym.bv_tpair(self.dirichlet_tag, w, dir_bc))
+                     ))
+                )
+
+    return result
+
+# }}}
+
+
+def rk4_step(y, t, h, f):
+    k1 = f(t, y)
+    k2 = f(t+h/2, y + h/2*k1)
+    k3 = f(t+h/2, y + h/2*k2)
+    k4 = f(t+h, y + h*k3)
+    return y + h/6*(k1 + 2*k2 + 2*k3 + k4)
+
+
+def main():
+    cl_ctx = cl.create_some_context()
+    queue = cl.CommandQueue(cl_ctx)
+
+    from meshmode.mesh.generation import generate_regular_rect_mesh
+    mesh = generate_regular_rect_mesh(
+            a=(-0.5, -0.5),
+            b=(0.5, 0.5),
+            n=(16, 16))
+
+    dt = 0.04
+
+    print("%d elements" % mesh.nelements)
+
+    discr = DGDiscretization(cl_ctx, mesh, order=4)
+
+    fields = join_fields(discr.zeros(queue),
+            [discr.zeros(queue) for i in range(discr.dim)])
+
+    from meshmode.discretization.visualization import make_visualizer
+    vis = make_visualizer(queue, discr.volume_discr, discr.order)
+
+    source_center = np.array([0.0, 0.05])
+    source_width = 0.05
+    source_omega = 3
+
+    def rhs(t, w):
+        queue = w[0].queue
+
+        nodes = discr.volume_discr.nodes().with_queue(queue)
+        center_dist = join_fields([
+            nodes[0] - source_center[0],
+            nodes[1] - source_center[1],
+            ])
+
+        source_f = (
+            np.sin(source_omega*t)
+            * clmath.exp(
+                -np.dot(center_dist, center_dist)
+                / source_width**2))
+        result = wave_operator(discr, c=1, w=w)
+        if t < 0.3:
+            result[0] = result[0] + source_f
+
+        return result
+
+    t = 0
+    t_final = 5
+    istep = 0
+    while t < t_final:
+        fields = rk4_step(fields, t, dt, rhs)
+
+        if istep % 2 == 0:
+            vis.write_vtk_file("fld-wave-min-%04d.vtu" % istep,
+                    [
+                        ("u", fields[0]),
+                        ("v", fields[1:]),
+                        ])
+
+        t += dt
+        istep += 1
+
+
+if __name__ == "__main__":
+    main()
+
+# vim: foldmethod=marker
-- 
GitLab


From 4b3392c593e908286a56de596c541a39731c5421 Mon Sep 17 00:00:00 2001
From: "[6~" <inform@tiker.net>
Date: Tue, 12 May 2020 00:55:48 -0500
Subject: [PATCH 2/4] Simple DG solver works

---
 examples/simple-dg.py | 110 ++++++++++++++++++++++++------------------
 1 file changed, 63 insertions(+), 47 deletions(-)

diff --git a/examples/simple-dg.py b/examples/simple-dg.py
index dc780f26..8fe6f706 100644
--- a/examples/simple-dg.py
+++ b/examples/simple-dg.py
@@ -24,6 +24,7 @@ THE SOFTWARE.
 
 
 import numpy as np
+import numpy.linalg as la  # noqa
 import pyopencl as cl
 import pyopencl.array as cla  # noqa
 import pyopencl.clmath as clmath
@@ -33,7 +34,7 @@ from pytools.obj_array import (
         with_object_array_or_scalar,
         is_obj_array)
 import loopy as lp
-from meshmode.mesh import BTAG_ALL  # noqa
+from meshmode.mesh import BTAG_ALL, BTAG_NONE  # noqa
 
 
 # Features lost vs. https://github.com/inducer/grudge:
@@ -137,8 +138,12 @@ class DGDiscretization:
             return self.interior_faces_connection()
         elif src_tgt == ("vol", "all_faces"):
             return self.all_faces_connection()
+        elif src_tgt == ("vol", BTAG_ALL):
+            return self.boundary_connection(tgt)
         elif src_tgt == ("int_faces", "all_faces"):
             return self.get_to_all_face_embedding(src)
+        elif src_tgt == (BTAG_ALL, "all_faces"):
+            return self.get_to_all_face_embedding(src)
         else:
             raise ValueError(f"locations '{src}'->'{tgt}' not understood")
 
@@ -156,6 +161,8 @@ class DGDiscretization:
             return self.all_faces_connection().to_discr
         elif where == "int_faces":
             return self.interior_faces_connection().to_discr
+        elif where == BTAG_ALL:
+            return self.boundary_connection(where).to_discr
         else:
             raise ValueError(f"location '{where}' not understood")
 
@@ -215,7 +222,8 @@ class DGDiscretization:
             ((a,), (b,)) = with_queue(
                     queue, parametrization_derivative(queue, bdry_discr))
 
-            return without_queue(join_fields(b, -a))
+            nrm = 1/(a**2+b**2)**0.5
+            return without_queue(join_fields(b*nrm, -a*nrm))
 
     @memoize_method
     def face_jacobian(self, where):
@@ -241,7 +249,7 @@ class DGDiscretization:
     def inverse_mass(self, vec):
         if is_obj_array(vec):
             return with_object_array_or_scalar(
-                    lambda el: self.face_mass(el), vec)
+                    lambda el: self.inverse_mass(el), vec)
 
         @memoize_in(self, "elwise_linear_knl")
         def knl():
@@ -258,12 +266,12 @@ class DGDiscretization:
 
         discr = self.volume_discr
 
-        result = discr.empty(queue=self.queue, dtype=vec.dtype)
+        result = discr.empty(queue=vec.queue, dtype=vec.dtype)
 
         for grp in discr.groups:
             matrix = self.get_inverse_mass_matrix(grp, vec.dtype)
 
-            knl()(self.queue, mat=matrix, result=grp.view(result),
+            knl()(vec.queue, mat=matrix, result=grp.view(result),
                     vec=grp.view(vec))
 
         return result/self.vol_jacobian()
@@ -318,6 +326,9 @@ class DGDiscretization:
 
         result = vol_discr.empty(queue=vec.queue, dtype=vec.dtype)
 
+        fj = self.face_jacobian("all_faces")
+        vec = vec*fj
+
         assert len(all_faces_discr.groups) == len(vol_discr.groups)
 
         for afgrp, volgrp in zip(all_faces_discr.groups, vol_discr.groups):
@@ -330,7 +341,7 @@ class DGDiscretization:
             knl()(vec.queue, mat=matrix, result=volgrp.view(result),
                     vec=input_view)
 
-        return result*self.face_jacobian("all_faces")
+        return result
 
 # }}}
 
@@ -410,24 +421,25 @@ def wave_operator(discr, c, w):
     u = w[0]
     v = w[1:]
 
-    # dir_u = discr.interp("vol", BTAG_ALL, u)
-    # dir_v = discr.interp("vol", BTAG_ALL, v)
-    # dir_bc = join_fields(-dir_u, dir_v)
+    dir_u = discr.interp("vol", BTAG_ALL, u)
+    dir_v = discr.interp("vol", BTAG_ALL, v)
+    dir_bval = join_fields(dir_u, dir_v)
+    dir_bc = join_fields(-dir_u, dir_v)
 
-    result = (
+    return (
             - join_fields(
                 -c*discr.div(v),
                 -c*discr.grad(u)
                 )
-             +  # noqa: W504
-             discr.inverse_mass(
-                 discr.face_mass(
-                     wave_flux(discr, c=c, w_tpair=interior_trace_pair(discr, w))
-                     #+ flux(sym.bv_tpair(self.dirichlet_tag, w, dir_bc))
-                     ))
+            +  # noqa: W504
+            discr.inverse_mass(
+                discr.face_mass(
+                    wave_flux(discr, c=c, w_tpair=interior_trace_pair(discr, w))
+                    + wave_flux(discr, c=c, w_tpair=TracePair(
+                        BTAG_ALL, dir_bval, dir_bc))
+                    ))
                 )
 
-    return result
 
 # }}}
 
@@ -440,59 +452,63 @@ def rk4_step(y, t, h, f):
     return y + h/6*(k1 + 2*k2 + 2*k3 + k4)
 
 
+def bump(discr, queue, t=0):
+    source_center = np.array([0.0, 0.05])
+    source_width = 0.05
+    source_omega = 3
+
+    nodes = discr.volume_discr.nodes().with_queue(queue)
+    center_dist = join_fields([
+        nodes[0] - source_center[0],
+        nodes[1] - source_center[1],
+        ])
+
+    return (
+        np.cos(source_omega*t)
+        * clmath.exp(
+            -np.dot(center_dist, center_dist)
+            / source_width**2))
+
+
 def main():
     cl_ctx = cl.create_some_context()
     queue = cl.CommandQueue(cl_ctx)
 
+    nel_1d = 16
     from meshmode.mesh.generation import generate_regular_rect_mesh
     mesh = generate_regular_rect_mesh(
             a=(-0.5, -0.5),
             b=(0.5, 0.5),
-            n=(16, 16))
+            n=(nel_1d, nel_1d))
+
+    order = 3
 
-    dt = 0.04
+    # no deep meaning here, just a fudge factor
+    dt = 0.75/(nel_1d*order**2)
 
     print("%d elements" % mesh.nelements)
 
-    discr = DGDiscretization(cl_ctx, mesh, order=4)
+    discr = DGDiscretization(cl_ctx, mesh, order=order)
 
-    fields = join_fields(discr.zeros(queue),
-            [discr.zeros(queue) for i in range(discr.dim)])
+    fields = join_fields(
+            bump(discr, queue),
+            [discr.zeros(queue) for i in range(discr.dim)]
+            )
 
     from meshmode.discretization.visualization import make_visualizer
-    vis = make_visualizer(queue, discr.volume_discr, discr.order)
-
-    source_center = np.array([0.0, 0.05])
-    source_width = 0.05
-    source_omega = 3
+    vis = make_visualizer(queue, discr.volume_discr, discr.order+3)
 
     def rhs(t, w):
-        queue = w[0].queue
-
-        nodes = discr.volume_discr.nodes().with_queue(queue)
-        center_dist = join_fields([
-            nodes[0] - source_center[0],
-            nodes[1] - source_center[1],
-            ])
-
-        source_f = (
-            np.sin(source_omega*t)
-            * clmath.exp(
-                -np.dot(center_dist, center_dist)
-                / source_width**2))
-        result = wave_operator(discr, c=1, w=w)
-        if t < 0.3:
-            result[0] = result[0] + source_f
-
-        return result
+        return wave_operator(discr, c=1, w=w)
 
     t = 0
-    t_final = 5
+    t_final = 3
     istep = 0
     while t < t_final:
         fields = rk4_step(fields, t, dt, rhs)
 
-        if istep % 2 == 0:
+        if istep % 10 == 0:
+            print(istep, t, la.norm(fields[0].get()))
             vis.write_vtk_file("fld-wave-min-%04d.vtu" % istep,
                     [
                         ("u", fields[0]),
-- 
GitLab


From f3c61c4f4344f7971df2b9458156c7291170057f Mon Sep 17 00:00:00 2001
From: "[6~" <inform@tiker.net>
Date: Tue, 12 May 2020 00:57:58 -0500
Subject: [PATCH 3/4] Whip examples into shape for automatic testing

---
 examples/multiple-meshes.py                        | 6 +++++-
 {examples => experiments}/refinement-playground.py | 0
 2 files changed, 5 insertions(+), 1 deletion(-)
 rename {examples => experiments}/refinement-playground.py (100%)

diff --git a/examples/multiple-meshes.py b/examples/multiple-meshes.py
index 84918e17..2dab3fab 100644
--- a/examples/multiple-meshes.py
+++ b/examples/multiple-meshes.py
@@ -1,6 +1,7 @@
 from __future__ import division
 
 import numpy as np  # noqa
+import sys
 
 
 order = 4
@@ -20,7 +21,10 @@ def main():
     draw_2d_mesh(mesh, set_bounding_box=True)
 
     import matplotlib.pyplot as pt
-    pt.show()
+    if sys.stdin.isatty():
+        pt.show()
+    else:
+        pt.savefig("plot.pdf")
 
 if __name__ == "__main__":
     main()
diff --git a/examples/refinement-playground.py b/experiments/refinement-playground.py
similarity index 100%
rename from examples/refinement-playground.py
rename to experiments/refinement-playground.py
-- 
GitLab


From 180beb9b3e21570f059ba57b0cd272b4b2084f92 Mon Sep 17 00:00:00 2001
From: "[6~" <inform@tiker.net>
Date: Tue, 12 May 2020 01:01:44 -0500
Subject: [PATCH 4/4] Add Gitlab CI to run examples

---
 examples/.gitignore | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 examples/.gitignore

diff --git a/examples/.gitignore b/examples/.gitignore
new file mode 100644
index 00000000..a1363379
--- /dev/null
+++ b/examples/.gitignore
@@ -0,0 +1 @@
+*.pdf
-- 
GitLab