Make list compression arg a list instead of a bool

This merge req enables ListOfListBuilder to decide which list to compress.

pyopencl/algorithm.py

@@ -649,7 +649,7 @@ void ${kernel_name}(${kernel_list_arg_decl} USER_ARG_DECL index_type n)
                 %if name not in count_sharing:
                     index_type plb_${name}_index;
                     if (plb_${name}_start_index)
-                        %if eliminate_empty_output_lists:
+                        %if name in eliminate_empty_output_lists:
                             plb_${name}_index =
                                 plb_${name}_start_index[
                                     ${name}_compressed_indices[i]
@@ -745,7 +745,7 @@ class ListOfListsBuilder:
             arg_decls, count_sharing=None, devices=None,
             name_prefix="plb_build_list", options=[], preamble="",
             debug=False, complex_kernel=False,
-            eliminate_empty_output_lists=False):
+            eliminate_empty_output_lists=[]):
         """
         :arg context: A :class:`pyopencl.Context`.
         :arg list_names_and_dtypes: a list of `(name, dtype)` tuples
@@ -760,6 +760,8 @@ class ListOfListsBuilder:
         :arg options: OpenCL compilation options for kernels using
             *generate_template*.
         :arg complex_kernel: If `True`, prevents vectorization on CPUs.
+        :arg eliminate_empty_output_lists: A Python list of list names
+            for which the empty output lists are eliminated.
 
         *generate_template* may use the following C macros/identifiers:
 
@@ -793,6 +795,11 @@ class ListOfListsBuilder:
         and a second time, for a 'generation' stage where the lists are
         actually filled. A `generate` function that has side effects beyond
         calling `append` is therefore ill-formed.
+
+        .. versionchanged:: 2018.1
+
+            Change *eliminate_empty_output_lists* argument type from `bool` to
+            `list`.
         """
 
         if devices is None:
@@ -819,7 +826,20 @@ class ListOfListsBuilder:
         self.debug = debug
 
         self.complex_kernel = complex_kernel
+
+        if eliminate_empty_output_lists is True:
+            eliminate_empty_output_lists = \
+                    [name for name, _ in self.list_names_and_dtypes]
+
+        if eliminate_empty_output_lists is False:
+            eliminate_empty_output_lists = []
+
         self.eliminate_empty_output_lists = eliminate_empty_output_lists
+        for list_name in self.eliminate_empty_output_lists:
+            if not any(list_name == name for name, _ in self.list_names_and_dtypes):
+                raise ValueError(
+                    "invalid list name '%s' in eliminate_empty_output_lists"
+                    % list_name)
 
     # {{{ kernel generators
 
@@ -950,7 +970,7 @@ class ListOfListsBuilder:
             kernel_list_args.append(
                     VectorArg(index_dtype, "plb_%s_start_index" % name))
 
-            if self.eliminate_empty_output_lists:
+            if name in self.eliminate_empty_output_lists:
                 kernel_list_args.append(
                     VectorArg(index_dtype, "%s_compressed_indices" % name))
 
@@ -1030,9 +1050,9 @@ class ListOfListsBuilder:
 
               This implies that all lists are contiguous.
 
-            If the *eliminate_empty_output_lists* constructor argument is set to
-            True, *lists* has two additional attributes ``num_nonempty_lists`` and
-            ``nonempty_indices``
+            If the list name is specified in *eliminate_empty_output_lists*
+            constructor argument, *lists* has two additional attributes
+            ``num_nonempty_lists`` and ``nonempty_indices``
 
             * ``num_nonempty_lists`` for the number of nonempty lists.
             * ``nonempty_indices`` for the index of nonempty list in input objects.
@@ -1091,7 +1111,7 @@ class ListOfListsBuilder:
 
             # The scan will turn the "counts" array into the "starts" array
             # in-place.
-            if self.eliminate_empty_output_lists:
+            if name in self.eliminate_empty_output_lists:
                 result[name] = BuiltList(count=None, starts=counts, lists=None,
                                          num_nonempty_lists=None,
                                          nonempty_indices=None)
@@ -1115,33 +1135,34 @@ class ListOfListsBuilder:
                 *(tuple(count_list_args) + args + (n_objects,)),
                 **dict(wait_for=wait_for))
 
-        if self.eliminate_empty_output_lists:
-            compress_events = {}
-            for name, dtype in self.list_names_and_dtypes:
-                if name in omit_lists:
-                    continue
-                if name in self.count_sharing:
-                    continue
-
-                compressed_counts = cl.array.empty(
-                    queue, (n_objects + 1,), index_dtype, allocator=allocator)
-                info_record = result[name]
-                info_record.nonempty_indices = cl.array.empty(
-                    queue, (n_objects + 1,), index_dtype, allocator=allocator)
-                info_record.num_nonempty_lists = cl.array.empty(
-                    queue, (1,), index_dtype, allocator=allocator)
-                info_record.compressed_indices = cl.array.empty(
-                    queue, (n_objects + 1,), index_dtype, allocator=allocator)
-                info_record.compressed_indices[0] = 0
-                compress_events[name] = compress_kernel(
-                    info_record.starts,
-                    compressed_counts,
-                    info_record.nonempty_indices,
-                    info_record.compressed_indices,
-                    info_record.num_nonempty_lists,
-                    wait_for=[count_event] + info_record.compressed_indices.events)
-
-                info_record.starts = compressed_counts
+        compress_events = {}
+        for name, dtype in self.list_names_and_dtypes:
+            if name in omit_lists:
+                continue
+            if name in self.count_sharing:
+                continue
+            if name not in self.eliminate_empty_output_lists:
+                continue
+
+            compressed_counts = cl.array.empty(
+                queue, (n_objects + 1,), index_dtype, allocator=allocator)
+            info_record = result[name]
+            info_record.nonempty_indices = cl.array.empty(
+                queue, (n_objects + 1,), index_dtype, allocator=allocator)
+            info_record.num_nonempty_lists = cl.array.empty(
+                queue, (1,), index_dtype, allocator=allocator)
+            info_record.compressed_indices = cl.array.empty(
+                queue, (n_objects + 1,), index_dtype, allocator=allocator)
+            info_record.compressed_indices[0] = 0
+            compress_events[name] = compress_kernel(
+                info_record.starts,
+                compressed_counts,
+                info_record.nonempty_indices,
+                info_record.compressed_indices,
+                info_record.num_nonempty_lists,
+                wait_for=[count_event] + info_record.compressed_indices.events)
+
+            info_record.starts = compressed_counts
 
         # {{{ run scans
 
@@ -1154,7 +1175,7 @@ class ListOfListsBuilder:
                 continue
 
             info_record = result[name]
-            if self.eliminate_empty_output_lists:
+            if name in self.eliminate_empty_output_lists:
                 compress_events[name].wait()
                 num_nonempty_lists = info_record.num_nonempty_lists.get()[0]
                 info_record.num_nonempty_lists = num_nonempty_lists
@@ -1164,7 +1185,7 @@ class ListOfListsBuilder:
                 info_record.starts[-1] = 0
 
             starts_ary = info_record.starts
-            if self.eliminate_empty_output_lists:
+            if name in self.eliminate_empty_output_lists:
                 evt = scan_kernel(
                         starts_ary,
                         size=info_record.num_nonempty_lists,
@@ -1209,7 +1230,7 @@ class ListOfListsBuilder:
             if name not in self.count_sharing:
                 write_list_args.append(info_record.starts.data)
 
-            if self.eliminate_empty_output_lists:
+            if name in self.eliminate_empty_output_lists:
                 write_list_args.append(info_record.compressed_indices.data)
 
         # }}}