Geometry Nodes: multi threaded field evaluation

This adds a new `ParallelMultiFunction` which wraps another multi-function
and evaluates it with multiple threads. The speeds up field evaluation
quite a bit (the effect is most noticeable when the number of evaluations
and the field is large).

There are still other single-threaded performance bottlenecks in field
evaluation that will need to be solved separately. Most notably here
is the process of copying the computed data into the position attribute
in the Set Position node.

Differential Revision: https://developer.blender.org/D12457

1 files changed, 39 insertions, 0 deletions

diff --git a/source/blender/functions/FN_multi_function_parallel.hh b/source/blender/functions/FN_multi_function_parallel.hh
new file mode 100644
index 00000000000..84c57efd434
--- /dev/null
+++ b/source/blender/functions/FN_multi_function_parallel.hh
@@ -0,0 +1,39 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+#pragma once
+
+/** \file
+ * \ingroup fn
+ */
+
+#include "FN_multi_function.hh"
+
+namespace blender::fn {
+
+class ParallelMultiFunction : public MultiFunction {
+ private:
+  const MultiFunction &fn_;
+  const int64_t grain_size_;
+  bool threading_supported_;
+
+ public:
+  ParallelMultiFunction(const MultiFunction &fn, const int64_t grain_size);
+
+  void call(IndexMask mask, MFParams params, MFContext context) const override;
+};
+
+}  // namespace blender::fn