From 7dc4ed00c0a23248e2c5e48333786b0c2341d0fa Mon Sep 17 00:00:00 2001
From: Tor Egge <Tor.Egge@online.no>
Date: Fri, 30 Sep 2022 12:01:36 +0200
Subject: Extend class comment with short description of memory layout for
 stored tensor.

---
 .../src/vespa/searchlib/tensor/tensor_buffer_operations.cpp   | 10 +++++-----
 .../src/vespa/searchlib/tensor/tensor_buffer_operations.h     | 11 +++++++++++
 2 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/searchlib/src/vespa/searchlib/tensor/tensor_buffer_operations.cpp b/searchlib/src/vespa/searchlib/tensor/tensor_buffer_operations.cpp
index ba8b550a779..807975c392a 100644
--- a/searchlib/src/vespa/searchlib/tensor/tensor_buffer_operations.cpp
+++ b/searchlib/src/vespa/searchlib/tensor/tensor_buffer_operations.cpp
@@ -35,23 +35,23 @@ adjust_min_alignment(size_t min_alignment)
     return std::max(std::max(sizeof(uint32_t), sizeof(string_id)), min_alignment);
 }
 
-struct MyFastValueView final : Value {
+struct FastValueView final : Value {
     const ValueType& _type;
     StringIdVector   _labels;
     FastValueIndex   _index;
     TypedCells       _cells;
-    MyFastValueView(const ValueType& type, ConstArrayRef<string_id> labels, TypedCells cells, size_t num_mapped_dimensions, size_t num_subspaces);
+    FastValueView(const ValueType& type, ConstArrayRef<string_id> labels, TypedCells cells, size_t num_mapped_dimensions, size_t num_subspaces);
     const ValueType& type() const override { return _type; }
     const Value::Index& index() const override { return _index; }
     TypedCells cells() const override { return _cells; }
     MemoryUsage get_memory_usage() const override {
-        MemoryUsage usage = self_memory_usage<MyFastValueView>();
+        MemoryUsage usage = self_memory_usage<FastValueView>();
         usage.merge(_index.map.estimate_extra_memory_usage());
         return usage;
     }
 };
 
-MyFastValueView::MyFastValueView(const ValueType& type, ConstArrayRef<string_id> labels, TypedCells cells, size_t num_mapped_dimensions, size_t num_subspaces)
+FastValueView::FastValueView(const ValueType& type, ConstArrayRef<string_id> labels, TypedCells cells, size_t num_mapped_dimensions, size_t num_subspaces)
     : Value(),
       _type(type),
       _labels(labels.begin(), labels.end()),
@@ -144,7 +144,7 @@ TensorBufferOperations::make_fast_view(ConstArrayRef<char> buf, const vespalib::
     auto cells_start_offset = get_cells_offset(num_subspaces, alignment);
     TypedCells cells(buf.data() + cells_start_offset, _cell_type, cells_size);
     assert(cells_start_offset + cells_mem_size <= buf.size());
-    return std::make_unique<MyFastValueView>(tensor_type, labels, cells, _num_mapped_dimensions, num_subspaces);
+    return std::make_unique<FastValueView>(tensor_type, labels, cells, _num_mapped_dimensions, num_subspaces);
 }
 
 void
diff --git a/searchlib/src/vespa/searchlib/tensor/tensor_buffer_operations.h b/searchlib/src/vespa/searchlib/tensor/tensor_buffer_operations.h
index 72b00e79426..ab3777d7526 100644
--- a/searchlib/src/vespa/searchlib/tensor/tensor_buffer_operations.h
+++ b/searchlib/src/vespa/searchlib/tensor/tensor_buffer_operations.h
@@ -23,6 +23,17 @@ namespace search::tensor {
 /*
  * Class used to store a tensor in a buffer and make tensor views based on
  * buffer content.
+ *
+ * Layout of buffer is:
+ *
+ * num_subspaces                                     - number of subspaces
+ * labels[num_subspaces * _num_mapped_dimensions]    - array of labels for sparse dimensions
+ * padding                                           - to align start of cells
+ * cells[num_subspaces * _dense_subspaces_size]      - array of tensor cell values
+ * padding                                           - to align start of next buffer
+ *
+ * Alignment is dynamic, based on cell type, memory used by tensor cell values and
+ * alignment required for reading num_subspaces and labels array.
  */
 class TensorBufferOperations
 {
-- 
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