Improve tag_inames interface: strings, like.INAME, unused.[gl]

doc/reference.rst

@@ -59,18 +59,18 @@ are accepted, in addition to what is registered in :mod:`pyopencl`.
 Iname Implementation Tags
 -------------------------
 
-========================= ====================================================
-Tag                       Meaning
-========================= ====================================================
-``None`` | ``"for"``      Sequential loop
-``"l.N"``                 Local (intra-group) axis N
-``"g.N"``                 Group-number axis N
-``"unr"``                 Unroll
-``"ilp"`` | ``"ilp.unr"`` Unroll using instruction-level parallelism
-``"ilp.seq"``             Realize parallel iname as innermost loop
-========================= ====================================================
-
-.. "l.auto" intentionally undocumented
+=============================== ====================================================
+Tag                             Meaning
+=============================== ====================================================
+``None`` | ``"for"``            Sequential loop
+``"l.N"``                       Local (intra-group) axis N ("local")
+``"g.N"``                       Group-number axis N ("group")
+``"unr"``                       Unroll
+``"ilp"`` | ``"ilp.unr"``       Unroll using instruction-level parallelism
+``"ilp.seq"``                   Realize parallel iname as innermost loop
+``"like.INAME"``                Can be used when tagging inames to tag like another
+``"unused.g"`` | ``"unused.l"`` Can be to tag as the next unused group/local axis
+=============================== ====================================================
 
 (Throughout this table, `N` must be replaced by an actual, zero-based number.)
 

loopy/transform/iname.py

@@ -542,16 +542,46 @@ def join_inames(kernel, inames, new_iname=None, tag=None, within=None):
 # {{{ tag inames
 
 def tag_inames(kernel, iname_to_tag, force=False, ignore_nonexistent=False):
-    from loopy.kernel.data import parse_tag
+    """Tag an iname
 
-    iname_to_tag = dict((iname, parse_tag(tag))
-            for iname, tag in six.iteritems(iname_to_tag))
+    :arg iname_to_tag: a list of tuple ``(iname, new_tag)``. *new_tag* is given
+        as an instance of a subclass of :class:`loopy.kernel.data.IndexTag` or
+        as a string as shown in :ref:`iname-tags`. May also be a dictionary
+        for backwards compatibility.
+    """
+
+    if isinstance(iname_to_tag, dict):
+        iname_to_tag = list(six.iteritems(iname_to_tag))
+    elif isinstance(iname_to_tag, str):
+        def parse_kv(s):
+            colon_index = s.find(":")
+            if colon_index == -1:
+                raise ValueError("tag decl '%s' has no colon" % s)
+
+            return (s[:colon_index].strip(), s[colon_index+1:].strip())
+
+        iname_to_tag = [parse_kv(s) for s in iname_to_tag.split(",")]
+
+    from loopy.kernel.data import parse_tag as inner_parse_tag
+
+    def parse_tag(tag):
+        if isinstance(tag, str):
+            if tag.startswith("like."):
+                return kernel.iname_to_tag.get(tag[5:])
+            elif tag == "unused.g":
+                return find_unused_axis_tag(kernel, "g")
+            elif tag == "unused.l":
+                return find_unused_axis_tag(kernel, "l")
+
+        return inner_parse_tag(tag)
+
+    iname_to_tag = [(iname, parse_tag(tag)) for iname, tag in iname_to_tag]
 
     from loopy.kernel.data import (ParallelTag, AutoLocalIndexTagBase,
             ForceSequentialTag)
 
     new_iname_to_tag = kernel.iname_to_tag.copy()
-    for iname, new_tag in six.iteritems(iname_to_tag):
+    for iname, new_tag in iname_to_tag:
         if iname not in kernel.all_inames():
             if ignore_nonexistent:
                 continue