Enable quantization fallback to non-quantized mode

Author: rfsaliev

src/VecSim/algorithms/svs/svs_utils.h

@@ -10,6 +10,7 @@
 #include <cstdint>
 #include <cstdlib>
 #include <string>
+#include <utility>
 
 namespace svs_details {
 // VecSim->SVS data type conversion
@@ -149,12 +150,23 @@ inline bool check_cpuid() {
 }
 // clang-format on
 
-inline bool isSVSLVQModeSupported(VecSimSvsQuantBits quant_bits) {
-    return quant_bits == VecSimSvsQuant_NONE
+// Check if the SVS implementation supports Qquantization mode
+// @param quant_bits requested SVS quantization mode
+// @return pair<fallbackMode, bool>
+inline std::pair<VecSimSvsQuantBits, bool> isSVSQuantBitsSupported(VecSimSvsQuantBits quant_bits) {
+    // If HAVE_SVS_LVQ is not defined, we don't support any quantization mode
+    // else we check if the CPU supports SVS LVQ
+    bool supported = quant_bits == VecSimSvsQuant_NONE
 #if HAVE_SVS_LVQ
-           || check_cpuid() // Check if the CPU supports SVS LVQ
+                     || check_cpuid() // Check if the CPU supports SVS LVQ
 #endif
         ;
+
+    // If the quantization mode is not supported, we fallback to non-quantized mode
+    auto fallBack = supported ? quant_bits : VecSimSvsQuant_NONE;
+
+    // And always return true, as far as non-quantized mode is always supported
+    return std::make_pair(fallBack, true);
 }
 } // namespace svs_details
 

src/VecSim/index_factories/svs_factory.cpp

@@ -37,11 +37,12 @@ VecSimIndex *NewIndexImpl(const VecSimParams *params, bool is_normalized) {
 
 template <typename MetricType, typename DataType>
 VecSimIndex *NewIndexImpl(const VecSimParams *params, bool is_normalized) {
-    if (!svs_details::isSVSLVQModeSupported(params->algoParams.svsParams.quantBits)) {
-        return NULL;
-    }
+    // Ignore the 'supported' flag because we always fallback at least to the non-quantized mode
+    // elsewhere we got code coverage failure for the `supported==false` case
+    auto quantBits =
+        std::get<0>(svs_details::isSVSQuantBitsSupported(params->algoParams.svsParams.quantBits));
 
-    switch (params->algoParams.svsParams.quantBits) {
+    switch (quantBits) {
     case VecSimSvsQuant_NONE:
         return NewIndexImpl<MetricType, DataType, 0>(params, is_normalized);
     case VecSimSvsQuant_8:
@@ -97,7 +98,11 @@ constexpr size_t QuantizedVectorSize(size_t dims, size_t alignment = 0) {
 
 template <typename DataType>
 size_t QuantizedVectorSize(VecSimSvsQuantBits quant_bits, size_t dims, size_t alignment = 0) {
-    switch (quant_bits) {
+    // Ignore the 'supported' flag because we always fallback at least to the non-quantized mode
+    // elsewhere we got code coverage failure for the `supported==false` case
+    auto quantBits = std::get<0>(svs_details::isSVSQuantBitsSupported(quant_bits));
+
+    switch (quantBits) {
     case VecSimSvsQuant_NONE:
         return QuantizedVectorSize<DataType, 0>(dims, alignment);
     case VecSimSvsQuant_8:

tests/unit/test_svs.cpp

@@ -8,7 +8,7 @@
 
 #define ASSERT_INDEX(index)                                                                        \
     if (index == nullptr) {                                                                        \
-        if (svs_details::isSVSLVQModeSupported(TypeParam::get_quant_bits())) {                     \
+        if (std::get<1>(svs_details::isSVSQuantBitsSupported(TypeParam::get_quant_bits()))) {      \
             GTEST_FAIL() << "Failed to create SVS index";                                          \
         } else {                                                                                   \
             GTEST_SKIP() << "SVS LVQ is not supported.";                                           \
@@ -698,7 +698,10 @@ TYPED_TEST(SVSTest, resizeIndex) {
 
     // Initial capacity is rounded up to the block size.
     size_t extra_cap = n % bs == 0 ? 0 : bs - n % bs;
-    if constexpr (TypeParam::get_quant_bits() > 0) {
+    auto quantBits = TypeParam::get_quant_bits();
+    // Get the fallback quantization mode
+    quantBits = std::get<0>(svs_details::isSVSQuantBitsSupported(quantBits));
+    if (quantBits != VecSimSvsQuant_NONE) {
         // LVQDataset does not provide a capacity method
         extra_cap = 0;
     }
@@ -1460,7 +1463,10 @@ TYPED_TEST(SVSTest, testSizeEstimation) {
     // converted then to a number of elements.
     // IMHO, would be better to always interpret block size to a number of elements
     // rather than conversion to-from number of bytes
-    if (TypeParam::get_quant_bits() > 0) {
+    auto quantBits = TypeParam::get_quant_bits();
+    // Get the fallback quantization mode
+    quantBits = std::get<0>(svs_details::isSVSQuantBitsSupported(quantBits));
+    if (quantBits != VecSimSvsQuant_NONE) {
         // Extra data in LVQ vector
         const auto lvq_vector_extra = sizeof(svs::quantization::lvq::ScalarBundle);
         dim -= (lvq_vector_extra * 8) / TypeParam::get_quant_bits();