use more than 1byte for hashing based edge weights

[mschimek]

No description provided.

[Copilot]

Pull Request Overview

This PR refactors the edge weight generation system to support hashing-based edge weight generation and improve the test infrastructure. The main focus is implementing a deterministic, hash-based edge weight generator that ensures consistent weights for undirected edges regardless of edge direction.

• Introduced PerEdgeWeightGenerator base class with EdgeRange support for cleaner edge iteration
• Implemented hashing-based edge weight generation with proper undirected edge support
• Refactored test fixtures from specific "UniformWeight" to general "GeneralEdgeWeight" to support multiple weight generation types
• Added comprehensive test coverage for hashing-based weight generation

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
tests/edge_weights/edge_generation_test.cpp	Renamed test fixture to GeneralEdgeWeightTestFixture and added four new test cases for hashing-based edge weight generation across both edgelist and CSR representations
kagen/generators/generator.cpp	Updated CreateEdgeWeightGenerator to pass vertex_range parameter to HashingBasedEdgeWeightGenerator constructor
kagen/edgeweight_generators/per_edge_weight_generator.h	Refactored to use EdgeRange for unified edge iteration, added vertex_range_ member and constructor parameter
kagen/edgeweight_generators/hashing_based_generator.h	Updated constructor signature to accept VertexRange parameter
kagen/edgeweight_generators/hashing_based_generator.cpp	Implemented improved hash-based weight generation with undirected edge support (swapping u,v), better hash distribution using 128-bit arithmetic, and fallback behavior when xxHash is unavailable

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[Copilot]

The variables name and weight_range are extracted from test parameters but never used in the test body. Consider removing them to avoid confusion.

[Copilot]

The variables name and weight_range are extracted from test parameters but never used in the test body. Consider removing them to avoid confusion.

Suggested change

	std::string name = std::get<0>(GetParam());
	GeneratorFunc generate = std::get<1>(GetParam());
	const SInt n = 1000;
	const SInt m = 16 * n;
	const WeightRange weight_range{1, 100};
	kagen::KaGen generator(MPI_COMM_WORLD);
	generator.UseEdgeListRepresentation();
	generator.ConfigureEdgeWeightGeneration(
	kagen::EdgeWeightGeneratorType::HASHING_BASED, weight_range.first, weight_range.second);
	Graph graph = generate(generator, n, m);
	check_backedge_weight(graph);
	}
	TEST_P(GeneralEdgeWeightTestFixture, hashing_based_correct_backedge_weights_csr_representation) {
	std::string name = std::get<0>(GetParam());
	GeneratorFunc generate = std::get<1>(GetParam());
	const SInt n = 1000;
	const SInt m = 16 * n;
	const WeightRange weight_range{1, 100};
	kagen::KaGen generator(MPI_COMM_WORLD);
	generator.UseCSRRepresentation();
	generator.ConfigureEdgeWeightGeneration(
	kagen::EdgeWeightGeneratorType::HASHING_BASED, weight_range.first, weight_range.second);
	GeneratorFunc generate = std::get<1>(GetParam());
	const SInt n = 1000;
	const SInt m = 16 * n;
	kagen::KaGen generator(MPI_COMM_WORLD);
	generator.UseEdgeListRepresentation();
	generator.ConfigureEdgeWeightGeneration(
	kagen::EdgeWeightGeneratorType::HASHING_BASED, 1, 100);
	Graph graph = generate(generator, n, m);
	check_backedge_weight(graph);
	}
	TEST_P(GeneralEdgeWeightTestFixture, hashing_based_correct_backedge_weights_csr_representation) {
	GeneratorFunc generate = std::get<1>(GetParam());
	const SInt n = 1000;
	const SInt m = 16 * n;
	kagen::KaGen generator(MPI_COMM_WORLD);
	generator.UseCSRRepresentation();
	generator.ConfigureEdgeWeightGeneration(
	kagen::EdgeWeightGeneratorType::HASHING_BASED, 1, 100);

[Copilot]

Commented-out code should be removed. The previous error-throwing behavior has been replaced with returning -1, which could mask configuration errors. If xxHash is truly optional, consider documenting this behavior change or using a different sentinel value that won't be confused with valid weights.

Suggested change

	// ((void)u);
	// ((void)v);
	// throw std::runtime_error("xxHash is required for hashing based edge weights");
	return -1;
	throw std::runtime_error("xxHash is required for hashing based edge weights");

[Copilot]

The variable name is extracted from test parameters but never used in the test body. Consider removing it to avoid confusion.

[Copilot]

The variable name is extracted from test parameters but never used in the test body. Consider removing it to avoid confusion.