diff --git a/devito/arch/archinfo.py b/devito/arch/archinfo.py
index e679d7a785..fe0a15c3e0 100644
--- a/devito/arch/archinfo.py
+++ b/devito/arch/archinfo.py
@@ -808,6 +808,11 @@ class IntelDevice(Device):
 
     max_mem_trans_nbytes = 64
 
+    def __init__(self, *args, sub_group_size=32, **kwargs):
+        super().__init__(*args, **kwargs)
+
+        self.sub_group_size = sub_group_size
+
     @property
     def march(self):
         return ''
@@ -894,10 +899,10 @@ def march(cls):
 AMDGPUX = AmdDevice('amdgpuX')
 
 INTELGPUX = IntelDevice('intelgpuX')
-PVC = IntelDevice('pvc', max_threads_per_block=4096)  # Legacy codename for MAX GPUs
-INTELGPUMAX = IntelDevice('intelgpuMAX', max_threads_per_block=4096)
-MAX1100 = IntelDevice('max1100', max_threads_per_block=4096)
-MAX1550 = IntelDevice('max1550', max_threads_per_block=4096)
+PVC = IntelDevice('pvc')  # Legacy codename for MAX GPUs
+INTELGPUMAX = IntelDevice('intelgpuMAX')
+MAX1100 = IntelDevice('max1100')
+MAX1550 = IntelDevice('max1550')
 
 platform_registry = Platform.registry
 platform_registry['cpu64'] = get_platform  # Autodetection
diff --git a/devito/ir/iet/nodes.py b/devito/ir/iet/nodes.py
index 136e7bbfee..72307c5ac5 100644
--- a/devito/ir/iet/nodes.py
+++ b/devito/ir/iet/nodes.py
@@ -21,13 +21,14 @@
                                 Symbol)
 from devito.types.object import AbstractObject, LocalObject
 
-__all__ = ['Node', 'Block', 'Expression', 'Callable', 'Call', 'ExprStmt',
-           'Conditional', 'Iteration', 'List', 'Section', 'TimedList', 'Prodder',
-           'MetaCall', 'PointerCast', 'HaloSpot', 'Definition', 'ExpressionBundle',
-           'AugmentedExpression', 'Increment', 'Return', 'While', 'ListMajor',
-           'ParallelIteration', 'ParallelBlock', 'Dereference', 'Lambda',
-           'SyncSpot', 'Pragma', 'DummyExpr', 'BlankLine', 'ParallelTree',
-           'BusyWait', 'CallableBody', 'Transfer']
+__all__ = ['Node', 'MultiTraversable', 'Block', 'Expression', 'Callable',
+           'Call', 'ExprStmt', 'Conditional', 'Iteration', 'List', 'Section',
+           'TimedList', 'Prodder', 'MetaCall', 'PointerCast', 'HaloSpot',
+           'Definition', 'ExpressionBundle', 'AugmentedExpression',
+           'Increment', 'Return', 'While', 'ListMajor', 'ParallelIteration',
+           'ParallelBlock', 'Dereference', 'Lambda', 'SyncSpot', 'Pragma',
+           'DummyExpr', 'BlankLine', 'ParallelTree', 'BusyWait', 'UsingNamespace',
+           'CallableBody', 'Transfer']
 
 # First-class IET nodes
 
@@ -175,6 +176,15 @@ class ExprStmt(object):
     pass
 
 
+class MultiTraversable(Node):
+
+    """
+    An abstract base class for Nodes comprising more than one traversable children.
+    """
+
+    pass
+
+
 class List(Node):
 
     """A sequence of Nodes."""
@@ -740,7 +750,7 @@ def defines(self):
         return self.all_parameters
 
 
-class CallableBody(Node):
+class CallableBody(MultiTraversable):
 
     """
     The immediate child of a Callable.
@@ -1057,7 +1067,7 @@ class Lambda(Node):
     A callable C++ lambda function. Several syntaxes are possible; here we
     implement one of the common ones:
 
-        [captures](parameters){body}
+        [captures](parameters){body} SPECIAL [[attributes]]
 
     For more info about C++ lambda functions:
 
@@ -1071,14 +1081,21 @@ class Lambda(Node):
         The captures of the lambda function.
     parameters : list of Basic or expr-like, optional
         The objects in input to the lambda function.
+    special : list of Basic, optional
+        Placeholder for custom lambdas, to add in e.g. macros.
+    attributes : list of str, optional
+        The attributes of the lambda function.
     """
 
     _traversable = ['body']
 
-    def __init__(self, body, captures=None, parameters=None):
+    def __init__(self, body, captures=None, parameters=None, special=None,
+                 attributes=None):
         self.body = as_tuple(body)
         self.captures = as_tuple(captures)
         self.parameters = as_tuple(parameters)
+        self.special = as_tuple(special)
+        self.attributes = as_tuple(attributes)
 
     def __repr__(self):
         return "Lambda[%s](%s)" % (self.captures, self.parameters)
@@ -1178,6 +1195,19 @@ def periodic(self):
         return self._periodic
 
 
+class UsingNamespace(Node):
+
+    """
+    A C++ using namespace directive.
+    """
+
+    def __init__(self, namespace):
+        self.namespace = namespace
+
+    def __repr__(self):
+        return "<UsingNamespace(%s)>" % self.namespace
+
+
 class Pragma(Node):
 
     """
diff --git a/devito/ir/iet/visitors.py b/devito/ir/iet/visitors.py
index f6e266ed9d..d94f2f1d78 100644
--- a/devito/ir/iet/visitors.py
+++ b/devito/ir/iet/visitors.py
@@ -573,7 +573,7 @@ def visit_Callable(self, o):
         signature = self._gen_signature(o)
         return c.FunctionBody(signature, c.Block(body))
 
-    def visit_CallableBody(self, o):
+    def visit_MultiTraversable(self, o):
         body = []
         prev = None
         for i in o.children:
@@ -585,6 +585,9 @@ def visit_CallableBody(self, o):
                 body.extend(as_tuple(v))
         return c.Collection(body)
 
+    def visit_UsingNamespace(self, o):
+        return c.Statement('using namespace %s' % ccode(o.namespace))
+
     def visit_Lambda(self, o):
         body = []
         for i in o.children:
@@ -595,7 +598,15 @@ def visit_Lambda(self, o):
                 body.extend(as_tuple(v))
         captures = [str(i) for i in o.captures]
         decls = [i.inline() for i in self._args_decl(o.parameters)]
-        top = c.Line('[%s](%s)' % (', '.join(captures), ', '.join(decls)))
+        extra = []
+        if o.special:
+            extra.append(' ')
+            extra.append(' '.join(str(i) for i in o.special))
+        if o.attributes:
+            extra.append(' ')
+            extra.append(' '.join('[[%s]]' % i for i in o.attributes))
+        top = c.Line('[%s](%s)%s' %
+                     (', '.join(captures), ', '.join(decls), ''.join(extra)))
         return LambdaCollection([top, c.Block(body)])
 
     def visit_HaloSpot(self, o):
@@ -677,7 +688,7 @@ def visit_Operator(self, o, mode='all'):
         includes = self._operator_includes(o) + [blankline]
 
         # Namespaces
-        namespaces = [c.Statement('using namespace %s' % i) for i in o._namespaces]
+        namespaces = [self._visit(i) for i in o._namespaces]
         if namespaces:
             namespaces.append(blankline)
 
diff --git a/devito/symbolics/extended_sympy.py b/devito/symbolics/extended_sympy.py
index b8de8bade8..8ff49b5e5e 100644
--- a/devito/symbolics/extended_sympy.py
+++ b/devito/symbolics/extended_sympy.py
@@ -16,10 +16,10 @@
 __all__ = ['CondEq', 'CondNe', 'IntDiv', 'CallFromPointer',  # noqa
            'CallFromComposite', 'FieldFromPointer', 'FieldFromComposite',
            'ListInitializer', 'Byref', 'IndexedPointer', 'Cast', 'DefFunction',
-           'InlineIf', 'ReservedWord', 'Keyword', 'String', 'Macro', 'Class',
-           'MacroArgument', 'CustomType', 'Deref', 'Namespace', 'Rvalue',
-           'INT', 'FLOAT', 'DOUBLE', 'VOID', 'Null', 'SizeOf', 'rfunc',
-           'cast_mapper', 'BasicWrapperMixin']
+           'MathFunction', 'InlineIf', 'ReservedWord', 'Keyword', 'String',
+           'Macro', 'Class', 'MacroArgument', 'CustomType', 'Deref',
+           'Namespace', 'Rvalue', 'INT', 'FLOAT', 'DOUBLE', 'VOID', 'Null',
+           'SizeOf', 'rfunc', 'cast_mapper', 'BasicWrapperMixin']
 
 
 class CondEq(sympy.Eq):
@@ -541,8 +541,7 @@ class DefFunction(Function, Pickable):
         https://github.com/sympy/sympy/issues/4297
     """
 
-    __rargs__ = ('name', 'arguments')
-    __rkwargs__ = ('template',)
+    __rargs__ = ('name', 'arguments', 'template')
 
     def __new__(cls, name, arguments=None, template=None, **kwargs):
         if isinstance(name, str):
@@ -609,6 +608,12 @@ def _sympystr(self, printer):
     __reduce_ex__ = Pickable.__reduce_ex__
 
 
+class MathFunction(DefFunction):
+
+    # Supposed to involve real operands
+    is_commutative = True
+
+
 class InlineIf(sympy.Expr, Pickable):
 
     """
diff --git a/devito/symbolics/manipulation.py b/devito/symbolics/manipulation.py
index b4ea829b70..220e4d27b8 100644
--- a/devito/symbolics/manipulation.py
+++ b/devito/symbolics/manipulation.py
@@ -2,7 +2,7 @@
 from collections.abc import Iterable
 from functools import singledispatch
 
-from sympy import Pow, Add, Mul, Min, Max, SympifyError, Tuple, sympify
+from sympy import Pow, Add, Mul, Min, Max, S, SympifyError, Tuple, sympify
 from sympy.core.add import _addsort
 from sympy.core.mul import _mulsort
 
@@ -146,6 +146,11 @@ def _(expr, args, kwargs):
 
 @_uxreplace_handle.register(Mul)
 def _(expr, args, kwargs):
+    # Perform some basic simplifications at least
+    args = [i for i in args if i != 1]
+    if any(i == 0 for i in args):
+        return S.Zero
+
     if all(i.is_commutative for i in args):
         _mulsort(args)
         _eval_numbers(expr, args)
diff --git a/devito/symbolics/printer.py b/devito/symbolics/printer.py
index 6924ffffbd..fbaf2757d2 100644
--- a/devito/symbolics/printer.py
+++ b/devito/symbolics/printer.py
@@ -241,6 +241,8 @@ def _print_DefFunction(self, expr):
             template = ''
         return "%s%s(%s)" % (expr.name, template, ','.join(arguments))
 
+    _print_MathFunction = _print_DefFunction
+
     def _print_Fallback(self, expr):
         return expr.__str__()
 
diff --git a/tests/test_iet.py b/tests/test_iet.py
index 6ee6c13ca7..41bae75821 100644
--- a/tests/test_iet.py
+++ b/tests/test_iet.py
@@ -144,6 +144,26 @@ def test_list_denesting():
     assert str(l3) == str(l2)
 
 
+def test_lambda():
+    grid = Grid(shape=(4, 4, 4))
+    x, y, z = grid.dimensions
+
+    u = Function(name='u', grid=grid)
+
+    e0 = DummyExpr(u.indexed, 1)
+    e1 = DummyExpr(u.indexed, 2)
+
+    body = List(body=[e0, e1])
+    lam = Lambda(body, ['='], [u.indexed], attributes=['my_attr'])
+
+    assert str(lam) == """\
+[=](float *restrict u) [[my_attr]]
+{
+  u = 1;
+  u = 2;
+}"""
+
+
 def test_make_cpp_parfor():
     """
     Test construction of a C++ parallel for. This excites the IET construction