[MOD-10185] add SVS fp16 tests

[meiravgri]

Overview

This PR introduces a comprehensive test suite for FP16 data types in the SVS algorithm.
The new test file test_svs_fp16.cpp is adapted from the existing test_svs.cpp to specifically validate SVS functionality with float16 vectors across single-index, multi-index, and tiered index configuration.

Key Changes

New Test File: tests/unit/test_svs_fp16.cpp

Test Class Structure

The file introduces three specialized test classes:

1. FP16SVSTest: Core SVS functionality tests for single-index scenarios
2. FP16SVSMultiTest: Multi-index SVS tests (inherits from FP16SVSTest)
3. FP16SVSTieredIndexTest: Tiered index SVS tests (inherits from FP16SVSTest)

• Type Definitions: runs float16 with quantization modes:

  • VecSimSvsQuant_NONE
  • VecSimSvsQuant_8
  • VecSimSvsQuant_8x8_LeanVec

• Custom Vector Generation: Added GenerateVector() and GenerateAndAddVector() methods specifically for float16 with proper FP32→FP16 conversion

• Data Conversion: All vector operations use vecsim_types::FP32_to_FP16() and vecsim_types::FP16_to_FP32() for proper type conversion

Test Coverage

Total Test Count: 50 tests (31 core + 10 multi-index + 9 tiered index)

Core SVS Tests (FP16SVSTest - 31 tests)

All essential SVS functionality tests adapted for FP16, including both adapted tests from the original suite and new FP16-specific tests:

Adapted from original test suite (26 tests):

• Vector operations: svs_vector_add_test, svs_vector_update_test
• Bulk operations: svs_bulk_vectors_add_delete_test
• Index management: svs_indexing_same_vector, svs_reindexing_same_vector, svs_reindexing_same_vector_different_id
• Batch iteration: svs_batch_iterator, svs_batch_iterator_non_unique_scores, svs_batch_iterator_reset, svs_batch_iterator_corner_cases
• Index lifecycle: resizeIndex, svs_empty_index, test_delete_vector
• Search algorithms: svs_vector_search_test_ip, svs_vector_search_test_l2, svs_vector_search_test_cosine
• Performance optimization: preferAdHocOptimization, batchIteratorSwapIndices
• Metrics and queries: rangeQuery, rangeQueryCosine
• Debugging and info: test_svs_info, test_basic_svs_info_iterator, test_dynamic_svs_info_iterator
• Size estimation: testSizeEstimation
• Stress testing: sanity_reinsert_1280

New FP16-specific tests (5 tests):

• svs_vector_search_test: Enhanced vector search test adapted for FP16
• test_get_distance: Distance calculation validation for FP16
• quant_modes: Comprehensive quantization mode validation
• test_override_all: Vector override functionality testing
• scalar_quantization_query: Scalar quantization query validation

Multi-Index Tests (FP16SVSMultiTest - 10 tests)

Specialized tests for multi-index scenarios where multiple vectors can share the same label:

• vector_add_multiple_test: Adding multiple vectors with same label
• vector_search_test: Search functionality in multi-index context
• search_more_than_there_is: Edge case handling for search limits
• find_better_score: Score optimization in multi-vector scenarios
• find_better_score_after_pop: Score optimization after vector removal
• reindexing_same_vector_different_id: Reindexing with different IDs
• test_svs_info: Multi-index debug information validation
• test_basic_svs_info_iterator: Multi-index debug iterator testing
• rangeQuery: Range queries in multi-index context
• svs_batch_iterator_basic: Batch iteration for multi-index

Tiered Index Tests (FP16SVSTieredIndexTest - 9 tests)

Tests for tiered index architecture with background indexing:

• CreateIndexInstanceSingle/CreateIndexInstanceMulti: Index creation validation
• RangeTestSingle/RangeTestMulti: Range query testing for both configurations
• KNNSearch: K-nearest neighbor search in tiered context
• deleteVector/deleteVectorMulti: Vector deletion in tiered indexes
• BatchIteratorSingle/BatchIteratorMulti: Batch iteration for tiered indexes

Tests Excluded (17 tests)

Tests from the original test_svs.cpp that were intentionally not included, either because they are not relevant to For couldn't be reliably implemented with FP16 precision:

• Timeout tests: testTimeoutReturn_topK, testTimeoutReturn_range, testTimeoutReturn_batch_iterator
• Parameter validation: test_svs_parameter_combinations_and_defaults, test_svs_parameter_consistency_across_metrics
• Runtime parameter resolution: resolve_ws_search_runtime_params, resolve_bc_search_runtime_params, resolve_use_search_history_runtime_params, resolve_epsilon_runtime_params
• FP16 incompatible: svs_test_inf_score (infinity values not achievable with FP16)
• Redundant/irrelevant: testInitialSizeEstimation (covered by testSizeEstimation), joinSearchParams (type not relevant), FitMemoryTest (no-op), logging_runtime_params

Additional Infrastructure Changes

SVS Index Implementation Enhancements

Enhanced Vector Data Access (src/VecSim/algorithms/svs/svs.h)

• Implemented getStoredVectorDataByLabel(): Added comprehensive implementation for retrieving stored vector data by label (only supported for non-compressed indices, both single and multi-index configurations)

Query Result Debugging (src/VecSim/query_result_definitions.h)

• Debug Print Operators: Added operator<< for VecSimQueryResult and VecSimQueryReply to enable better test debugging
• Test-Only Features: Wrapped debug functionality in #ifdef BUILD_TESTS to keep production code clean
• Enhanced Error Messages: Improved test failure diagnostics with detailed query result information (validateTopKSearchTest() function now prints all results of the assertion fails: ASSERT_TRUE(allUniqueResults(res)) << *res;)

Test Infrastructure Improvements

Enhanced Test Utilities (tests/unit/unit_test_utils.cpp & .h)

• SVS Parameter Validation: Added validateSVSIndexAttributesInfo() function to validate SVS index parameters against svsInfoStruct values

Extended Test Data Generation (tests/utils/tests_utils.h)

• FP16 Vector Generation: Added populate_float16_vec() function for generating random FP16 test vectors