[PoC] Serialize any node as postponed constant - 2nd approach #32502

olpipi · 2025-10-21T15:41:26Z

Details:

Serialize any node as postponed constant

Tickets:

CVS-175021

mryzhov · 2025-10-22T07:11:08Z

src/core/dev_api/openvino/core/model_util.hpp

                                    const TensorNamesMap& outputs_names = {});

+
+OPENVINO_API std::shared_ptr<ov::Node> make_postponed_constant_from_node(std::shared_ptr<ov::Node> node);


just a kind reminder to add the short description and the new tests ;)

t-jankowski · 2025-10-22T09:26:15Z

src/core/src/op/util/posponed_constant.cpp

+
+class PostponedConstant : public ov::op::Op {
+public:
+    OPENVINO_OP("Constant", "opset1");


Mimic-ing Constant in such way is risky. Note that ov::is_type uses this and it may lead to issues elsewhere - ov::op::v0::Constant has exactly same definition.

Copilot

Pull Request Overview

This PR introduces a mechanism to serialize any node as a postponed constant, which delays constant folding until model serialization time. The implementation creates a special PostponedConstant operation that wraps a node and presents itself as a Constant op from opset1, but defers actual constant evaluation until the model is saved to IR format.

Key changes:

Implements PostponedConstant class that wraps arbitrary nodes and masquerades as Constants
Adds factory function to create and replace nodes with postponed constants
Exposes the factory function through the public API header

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 6 comments.

File	Description
src/core/src/op/util/posponed_constant.cpp	Implements PostponedConstant operation and factory function
src/core/dev_api/openvino/core/model_util.hpp	Adds public API declaration for postponed constant creation

_{Tip: Customize your code reviews with copilot-instructions.md. Create the file or learn how to get started.}

Copilot · 2025-10-22T11:08:57Z

src/core/src/op/util/posponed_constant.cpp

+    }
+
+    std::shared_ptr<Node> clone_with_new_inputs(const ov::OutputVector& inputs) const {
+        OPENVINO_THROW("PostponedConstant cannot be copied");


The clone_with_new_inputs method throws an exception unconditionally, but it doesn't verify or document that inputs should be empty (since PostponedConstant has no inputs). Consider adding a parameter validation and update the error message to be more descriptive: 'PostponedConstant cannot be cloned with new inputs'.

Suggested change

OPENVINO_THROW("PostponedConstant cannot be copied");

if (!inputs.empty()) {

OPENVINO_THROW("PostponedConstant cannot be cloned with new inputs; expected no inputs.");

}

OPENVINO_THROW("PostponedConstant cannot be cloned.");

Copilot · 2025-10-22T11:08:57Z

src/core/src/op/util/posponed_constant.cpp

+        ov::OutputVector outputs(1);
+        OPENVINO_ASSERT(
+            m_node->constant_fold(outputs, m_node->input_values()),
+            "Node with set `postponed_constant` attribute cannot be fold to constant when saving model to IR file");


The error message has a grammatical error. Change 'cannot be fold' to 'cannot be folded'.

Suggested change

"Node with set `postponed_constant` attribute cannot be fold to constant when saving model to IR file");

"Node with set `postponed_constant` attribute cannot be folded to constant when saving model to IR file");

Copilot · 2025-10-22T11:08:57Z

src/core/src/op/util/posponed_constant.cpp

+        constructor_validate_and_infer_types();
+    };
+
+    void validate_and_infer_types() {


The validate_and_infer_types method should be marked as override since it overrides a virtual method from the base Op class.

Suggested change

void validate_and_infer_types() {

void validate_and_infer_types() override {

Copilot · 2025-10-22T11:08:58Z

src/core/src/op/util/posponed_constant.cpp

+        set_output_type(0, output.get_element_type(), output.get_partial_shape());
+    }
+
+    std::shared_ptr<Node> clone_with_new_inputs(const ov::OutputVector& inputs) const {


The clone_with_new_inputs method should be marked as override since it overrides a virtual method from the base Op class.

Suggested change

std::shared_ptr<Node> clone_with_new_inputs(const ov::OutputVector& inputs) const {

std::shared_ptr<Node> clone_with_new_inputs(const ov::OutputVector& inputs) const override {

Copilot · 2025-10-22T11:08:58Z

src/core/src/op/util/posponed_constant.cpp

+        OPENVINO_THROW("PostponedConstant cannot be copied");
+    }
+
+    bool visit_attributes(AttributeVisitor& visitor) {


The visit_attributes method should be marked as override since it overrides a virtual method from the base Op class.

Suggested change

bool visit_attributes(AttributeVisitor& visitor) {

bool visit_attributes(AttributeVisitor& visitor) override {

Copilot · 2025-10-22T11:08:58Z

src/core/dev_api/openvino/core/model_util.hpp

+OPENVINO_API std::shared_ptr<ov::Node> make_postponed_constant_from_node(std::shared_ptr<ov::Node> node);
+


The new public API function make_postponed_constant_from_node lacks documentation. Add a docstring explaining the function's purpose, parameters, return value, and any preconditions (e.g., that the node must have exactly one output).

Suggested change

OPENVINO_API std::shared_ptr<ov::Node> make_postponed_constant_from_node(std::shared_ptr<ov::Node> node);

/**

* @brief Creates a postponed constant node from the given node.

*

* This function generates a constant node whose value is determined at a later stage,

* based on the output of the provided node. The input node must have exactly one output.

*

* @param node A shared pointer to the node from which to create the postponed constant.

* The node must have exactly one output.

* @return A shared pointer to the newly created postponed constant node.

*

* @note The input node must have exactly one output.

*/

OPENVINO_API std::shared_ptr<ov::Node> make_postponed_constant_from_node(std::shared_ptr<ov::Node> node);

mryzhov · 2025-10-22T11:14:32Z

I'm concerning about the path (src/core/src/op/util/posponed_constant.cpp), @mitruska could you advise the right place for the custom operations?

mitruska · 2025-10-22T11:24:52Z

I'm concerning about the path (src/core/src/op/util/posponed_constant.cpp), @mitruska could you advise the right place for the custom operations?

I assume the location is intentional, as it makes it hidden from public API and possible to used with this dedicated helper only.
It's not a regular custom op to be executed by plugins, and it shouldn't appear in IR.

olpipi requested a review from a team as a code owner October 21, 2025 15:41

olpipi added do not merge do_not_merge labels Oct 21, 2025

github-actions bot added the category: Core OpenVINO Core (aka ngraph) label Oct 21, 2025

olpipi force-pushed the postponed_constant_ext_2 branch 2 times, most recently from ac37557 to 24ce342 Compare October 21, 2025 18:33

Postponed constant

580ff3f

olpipi force-pushed the postponed_constant_ext_2 branch from 24ce342 to 580ff3f Compare October 21, 2025 18:35

mryzhov approved these changes Oct 22, 2025

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mryzhov reviewed Oct 22, 2025

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t-jankowski reviewed Oct 22, 2025

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mryzhov requested a review from Copilot October 22, 2025 11:07

Copilot AI reviewed Oct 22, 2025

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mryzhov mentioned this pull request Oct 23, 2025

Serialize any node as postponed constant #32490

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olpipi closed this Oct 24, 2025

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[PoC] Serialize any node as postponed constant - 2nd approach #32502

[PoC] Serialize any node as postponed constant - 2nd approach #32502

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		const TensorNamesMap& outputs_names = {});


		OPENVINO_API std::shared_ptr<ov::Node> make_postponed_constant_from_node(std::shared_ptr<ov::Node> node);

-        OPENVINO_THROW("PostponedConstant cannot be copied");
+        if (!inputs.empty()) {
+            OPENVINO_THROW("PostponedConstant cannot be cloned with new inputs; expected no inputs.");
+        }
+        OPENVINO_THROW("PostponedConstant cannot be cloned.");

	"Node with set `postponed_constant` attribute cannot be fold to constant when saving model to IR file");
	"Node with set `postponed_constant` attribute cannot be folded to constant when saving model to IR file");

	void validate_and_infer_types() {
	void validate_and_infer_types() override {

	std::shared_ptr<Node> clone_with_new_inputs(const ov::OutputVector& inputs) const {
	std::shared_ptr<Node> clone_with_new_inputs(const ov::OutputVector& inputs) const override {

	bool visit_attributes(AttributeVisitor& visitor) {
	bool visit_attributes(AttributeVisitor& visitor) override {

-OPENVINO_API std::shared_ptr<ov::Node> make_postponed_constant_from_node(std::shared_ptr<ov::Node> node);
+/**
+ * @brief Creates a postponed constant node from the given node.
+ *
+ * This function generates a constant node whose value is determined at a later stage,
+ * based on the output of the provided node. The input node must have exactly one output.
+ *
+ * @param node A shared pointer to the node from which to create the postponed constant.
+ *             The node must have exactly one output.
+ * @return A shared pointer to the newly created postponed constant node.
+ *
+ * @note The input node must have exactly one output.
+ */
+OPENVINO_API std::shared_ptr<ov::Node> make_postponed_constant_from_node(std::shared_ptr<ov::Node> node);

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[PoC] Serialize any node as postponed constant - 2nd approach #32502

[PoC] Serialize any node as postponed constant - 2nd approach #32502

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olpipi commented Oct 21, 2025

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