Prefix caching for NPU in nested plugin config structure

[mzegla]

No description provided.

[Copilot]

Pull request overview

This PR modifies the plugin configuration structure to support prefix caching for NPU devices by moving NPU-specific parameters into a nested DEVICE_PROPERTIES.NPU structure instead of keeping them at the top level.

Changes:

• Updated C++ code to check for and add NPUW_LLM_ENABLE_PREFIX_CACHING within the nested DEVICE_PROPERTIES.NPU structure
• Modified Python export script to create the nested structure for NPU-specific properties including MAX_PROMPT_LEN and NPUW_LLM_ENABLE_PREFIX_CACHING

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.

File	Description
src/graph_export/graph_export.cpp	Enhanced conflict detection to search both top-level and nested structures, and changed the insertion logic to add prefix caching parameter within DEVICE_PROPERTIES.NPU
demos/common/export_models/export_model.py	Removed top-level MAX_PROMPT_LEN assignment and consolidated NPU-specific properties into the nested DEVICE_PROPERTIES.NPU structure

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[Copilot]

After adding the member in line 621, the iterator lookup in line 622 is unnecessary. The AddMember operation returns void, but you can use the newly created deviceProps object directly or leverage the fact that the member was just added to avoid the redundant FindMember call. Consider storing a reference or iterator during creation to avoid this second lookup.

Suggested change

	devicePropsItr = d.FindMember("DEVICE_PROPERTIES");
	}
	auto npuItr = devicePropsItr->value.FindMember("NPU");
	if (npuItr == devicePropsItr->value.MemberEnd()) {
	rapidjson::Value npuObj(rapidjson::kObjectType);
	devicePropsItr->value.AddMember("NPU", npuObj, d.GetAllocator());
	npuItr = devicePropsItr->value.FindMember("NPU");
	devicePropsItr = d.MemberEnd();
	--devicePropsItr;
	}
	auto npuItr = devicePropsItr->value.FindMember("NPU");
	if (npuItr == devicePropsItr->value.MemberEnd()) {
	rapidjson::Value npuObj(rapidjson::kObjectType);
	devicePropsItr->value.AddMember("NPU", npuObj, d.GetAllocator());
	npuItr = devicePropsItr->value.MemberEnd();
	--npuItr;

[Copilot]

Similar to the DEVICE_PROPERTIES creation, after adding the NPU member in line 628, the FindMember call in line 629 is redundant. Consider refactoring to avoid this unnecessary lookup.

Suggested change

	devicePropsItr->value.AddMember("NPU", npuObj, d.GetAllocator());
	npuItr = devicePropsItr->value.FindMember("NPU");
	}
	npuItr->value.AddMember("NPUW_LLM_ENABLE_PREFIX_CACHING", value, d.GetAllocator());
	npuObj.AddMember("NPUW_LLM_ENABLE_PREFIX_CACHING", value, d.GetAllocator());
	devicePropsItr->value.AddMember("NPU", npuObj, d.GetAllocator());
	} else {
	npuItr->value.AddMember("NPUW_LLM_ENABLE_PREFIX_CACHING", value, d.GetAllocator());
	}

[Copilot]

The variable name 'device_properties' is ambiguous since it only contains NPU properties in this context. Consider renaming to 'npu_device_properties' or using a more descriptive name to clarify that this is specifically for NPU configuration.

Suggested change

	device_properties = { "NPU": npu_properties }
	plugin_config['DEVICE_PROPERTIES'] = device_properties
	npu_device_properties = { "NPU": npu_properties }
	plugin_config['DEVICE_PROPERTIES'] = npu_device_properties

[Copilot]

There is an extra blank line here. Consider removing this trailing whitespace to maintain consistent code formatting.

Suggested change