Merge branch 'master' into fix-boundary-emptiness-check

.gitlab-ci.yml

doc/conf.py

doc/index.rst

doc/symbolic.rst

examples/advection/weak.py

examples/dagrt-fusion.py

grudge/__init__.py

grudge/execution.py

grudge/function_registry.py

grudge/models/advection.py

grudge/models/em.py

grudge/sym.py

grudge/symbolic/__init__.py

grudge/symbolic/dofdesc_inference.py

grudge/symbolic/mappers/__init__.py

grudge/symbolic/operators.py

grudge/symbolic/primitives.py

test/test_grudge.py