[GitHub] [arrow] benibus commented on a diff in pull request #8510: GH-15483: [C++] Add a Fixed Shape Tensor canonical ExtensionType

["benibus (via GitHub)" <gi...@apache.org>]

benibus commented on code in PR #8510:
URL: https://github.com/apache/arrow/pull/8510#discussion_r1122068498


##########
cpp/src/arrow/extension/fixed_shape_tensor.h:
##########
@@ -0,0 +1,87 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+#include <numeric>
+#include <sstream>
+
+#include "arrow/extension_type.h"
+
+namespace arrow {
+namespace extension {
+
+class ARROW_EXPORT FixedShapeTensor : public ExtensionArray {
+ public:
+  using ExtensionArray::ExtensionArray;
+};
+
+/// \brief Concrete type class for constant-size Tensor data.
+class ARROW_EXPORT FixedShapeTensorType : public ExtensionType {
+ public:
+  FixedShapeTensorType(const std::shared_ptr<DataType>& value_type,
+                       const std::vector<int64_t>& shape,
+                       const std::vector<int64_t>& permutation = {},
+                       const std::vector<std::string>& dim_names = {})
+      : ExtensionType(get_storage_type(value_type, shape)),
+        value_type_(value_type),
+        shape_(shape),
+        permutation_(permutation),
+        dim_names_(dim_names) {}
+
+  std::string extension_name() const override;
+
+  size_t ndim() const;
+
+  std::vector<int64_t> shape() const;
+
+  std::vector<int64_t> strides() const;
+
+  std::vector<int64_t> permutation() const;
+
+  std::vector<std::string> dim_names() const;
+
+  bool ExtensionEquals(const ExtensionType& other) const override;
+
+  std::string Serialize() const override;
+
+  Result<std::shared_ptr<DataType>> Deserialize(
+      std::shared_ptr<DataType> storage_type,
+      const std::string& serialized_data) const override;

Review Comment:
   You could get away with accepting a `std::string_view` here instead (to avoid an unnecessary conversion+allocation).



##########
cpp/src/arrow/extension/fixed_shape_tensor.cc:
##########
@@ -0,0 +1,263 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+#include "arrow/extension/fixed_shape_tensor.h"
+
+#include "arrow/array/array_nested.h"
+#include "arrow/array/array_primitive.h"
+#include "arrow/json/rapidjson_defs.h"  // IWYU pragma: keep
+#include "arrow/tensor.h"
+#include "arrow/util/logging.h"
+#include "arrow/util/sort.h"
+
+#include <rapidjson/document.h>
+#include <rapidjson/writer.h>
+
+namespace rj = arrow::rapidjson;
+
+namespace arrow {
+namespace extension {
+
+std::string FixedShapeTensorType::extension_name() const {
+  return "arrow.fixed_shape_tensor";
+}
+
+size_t FixedShapeTensorType::ndim() const { return shape_.size(); }
+
+std::vector<int64_t> FixedShapeTensorType::shape() const { return shape_; }
+
+std::vector<int64_t> FixedShapeTensorType::strides() const {
+  std::vector<int64_t> strides;
+  const auto& value_type = internal::checked_cast<const FixedWidthType&>(*value_type_);
+  DCHECK_OK(internal::ComputeRowMajorStrides(value_type, shape_, &strides));
+  if (!permutation_.empty()) {
+    internal::Permute(permutation_, &strides);
+  }
+  return strides;
+}
+
+std::vector<int64_t> FixedShapeTensorType::permutation() const { return permutation_; }
+
+std::vector<std::string> FixedShapeTensorType::dim_names() const { return dim_names_; }
+
+bool FixedShapeTensorType::ExtensionEquals(const ExtensionType& other) const {
+  if (extension_name() != other.extension_name()) {
+    return false;
+  }
+  const auto& other_ext = static_cast<const FixedShapeTensorType&>(other);
+  bool equals = storage_type()->Equals(other_ext.storage_type());
+  equals &= shape_ == other_ext.shape();
+  equals &= permutation_ == other_ext.permutation();
+  equals &= dim_names_ == other_ext.dim_names();
+  return equals;
+}
+
+std::string FixedShapeTensorType::Serialize() const {
+  rj::Document document;
+  document.SetObject();
+  rj::Document::AllocatorType& allocator = document.GetAllocator();
+
+  rj::Value shape(rj::kArrayType);
+  for (auto v : shape_) {
+    shape.PushBack(v, allocator);
+  }
+  document.AddMember(rj::Value("shape", allocator), shape, allocator);
+
+  if (!permutation_.empty()) {
+    rj::Value permutation(rj::kArrayType);
+    for (auto v : permutation_) {
+      permutation.PushBack(v, allocator);
+    }
+    document.AddMember(rj::Value("permutation", allocator), permutation, allocator);
+  }
+
+  if (!dim_names_.empty()) {
+    rj::Value dim_names(rj::kArrayType);
+    for (std::string v : dim_names_) {
+      dim_names.PushBack(rj::Value{}.SetString(v.c_str(), allocator), allocator);
+    }
+    document.AddMember(rj::Value("dim_names", allocator), dim_names, allocator);
+  }
+
+  rj::StringBuffer buffer;
+  rj::Writer<rj::StringBuffer> writer(buffer);
+  document.Accept(writer);
+  return buffer.GetString();
+}
+
+Result<std::shared_ptr<DataType>> FixedShapeTensorType::Deserialize(
+    std::shared_ptr<DataType> storage_type, const std::string& serialized_data) const {
+  auto value_type =
+      internal::checked_pointer_cast<FixedSizeListType>(storage_type)->value_type();
+  rj::Document document;
+  if (document.Parse(serialized_data.data(), serialized_data.length()).HasParseError() ||
+      !document.HasMember("shape") || !document["shape"].IsArray()) {
+    return Status::Invalid("Invalid serialized JSON data: ", serialized_data);
+  }
+
+  std::vector<int64_t> shape;
+  for (auto& x : document["shape"].GetArray()) {
+    shape.emplace_back(x.GetInt64());
+  }
+  std::vector<int64_t> permutation;
+  if (document.HasMember("permutation")) {
+    for (auto& x : document["permutation"].GetArray()) {
+      permutation.emplace_back(x.GetInt64());
+    }
+    ARROW_CHECK_EQ(shape.size(), permutation.size()) << "Invalid permutation";

Review Comment:
   Is there a reason we're not returning an error here? Same with `dim_names` below.



##########
cpp/src/arrow/extension/fixed_shape_tensor.cc:
##########
@@ -0,0 +1,263 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+#include "arrow/extension/fixed_shape_tensor.h"
+
+#include "arrow/array/array_nested.h"
+#include "arrow/array/array_primitive.h"
+#include "arrow/json/rapidjson_defs.h"  // IWYU pragma: keep
+#include "arrow/tensor.h"
+#include "arrow/util/logging.h"
+#include "arrow/util/sort.h"
+
+#include <rapidjson/document.h>
+#include <rapidjson/writer.h>
+
+namespace rj = arrow::rapidjson;
+
+namespace arrow {
+namespace extension {
+
+std::string FixedShapeTensorType::extension_name() const {
+  return "arrow.fixed_shape_tensor";
+}
+
+size_t FixedShapeTensorType::ndim() const { return shape_.size(); }
+
+std::vector<int64_t> FixedShapeTensorType::shape() const { return shape_; }
+
+std::vector<int64_t> FixedShapeTensorType::strides() const {
+  std::vector<int64_t> strides;
+  const auto& value_type = internal::checked_cast<const FixedWidthType&>(*value_type_);
+  DCHECK_OK(internal::ComputeRowMajorStrides(value_type, shape_, &strides));
+  if (!permutation_.empty()) {
+    internal::Permute(permutation_, &strides);
+  }
+  return strides;
+}

Review Comment:
   I suspect this isn't trivial enough to warrant the lowercase name. `ComputeStrides` maybe? Or perhaps you could cache the result internally (either on construction or lazily) and return a `const&`.



##########
cpp/src/arrow/extension/fixed_shape_tensor.h:
##########
@@ -0,0 +1,87 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+#include <numeric>
+#include <sstream>
+
+#include "arrow/extension_type.h"
+
+namespace arrow {
+namespace extension {
+
+class ARROW_EXPORT FixedShapeTensor : public ExtensionArray {
+ public:
+  using ExtensionArray::ExtensionArray;
+};
+
+/// \brief Concrete type class for constant-size Tensor data.
+class ARROW_EXPORT FixedShapeTensorType : public ExtensionType {
+ public:
+  FixedShapeTensorType(const std::shared_ptr<DataType>& value_type,
+                       const std::vector<int64_t>& shape,
+                       const std::vector<int64_t>& permutation = {},
+                       const std::vector<std::string>& dim_names = {})
+      : ExtensionType(get_storage_type(value_type, shape)),
+        value_type_(value_type),
+        shape_(shape),
+        permutation_(permutation),
+        dim_names_(dim_names) {}
+
+  std::string extension_name() const override;
+
+  size_t ndim() const;
+
+  std::vector<int64_t> shape() const;

Review Comment:
   Should probably return `const std::vector<int64_t>&` instead. Similar with `permutation()` and `dim_names()`.



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