Add EmbeddingSpMDMNBitRowWiseSparse autovectorized variant (#5244)

Summary:

X-link: facebookresearch/FBGEMM#2235

This adds an autovectorized implementation of the `GenerateEmbeddingSpMDMNBitRowWiseSparse` kernels.

This first version is around 10x improvement compared to the reference C++ implementation, but slower than the asmjit verison (which is x86 only), see list below for how to close this gap:

Room for further enhacements (see some of the surrounding kernels that do implement them):
- This is only specialized for `bit_rate` right now. Specializing for common block sizes typically nets good improvements.
- Directly operates on the `out` buffer. This is good for unknown block-sizes, but if we specialize for fixed small block-sizes then a separate buffer is better as it can be promoted completely to vector registers (for fixed vector register size anyway, doesn't work for variable size AArch64 SVE registers).
- No prefetching logic yet.

Reviewed By: excelle08

Differential Revision: D89086019

Author: MatzeB

src/EmbeddingSpMDMAutovec.cc

@@ -538,6 +538,134 @@ static bool ALWAYS_INLINE EmbeddingSpMDMNBit_autovec(
   return current == index_size;
 }
 
+template <typename IndexType, typename OffsetType>
+static bool ALWAYS_INLINE EmbeddingSpMDMNBitRowWiseSparse_autovec(
+    const int bit_rate,
+    const int64_t block_size,
+    const int64_t output_size,
+    const int64_t index_size,
+    const int64_t uncompressed_data_size,
+    const uint8_t* input,
+    const IndexType* indices,
+    const int32_t* compressed_indices_table,
+    const OffsetType* offsets_or_lengths,
+    const float* weights,
+    const bool normalize_by_lengths,
+    float* out,
+    const bool is_weight_positional,
+    const bool use_offsets) {
+  if (uncompressed_data_size < 0) {
+    return false;
+  }
+
+  // block_size is the number of elements and fused_block_size is the size in
+  // bytes of an entire row, including scale and bias.
+  const int num_elem_per_byte = 8 / bit_rate;
+  const int64_t scale_bias_size = 2 * sizeof(float16);
+  const uint64_t scale_bias_offset = div_up(block_size, num_elem_per_byte);
+  const int64_t fused_block_size = scale_bias_offset + scale_bias_size;
+
+  int64_t current = 0;
+  float* buf = out;
+  for (int64_t m = 0; m < output_size; ++m) {
+    const OffsetType len = use_offsets
+        ? offsets_or_lengths[m + 1] - offsets_or_lengths[m]
+        : offsets_or_lengths[m];
+    const int64_t end = current + len;
+    if (end > index_size) {
+      return false;
+    }
+
+    memset(buf, 0, sizeof(float) * block_size);
+
+    const float* weights_addr = weights != nullptr
+        ? (is_weight_positional ? weights : weights + current)
+        : nullptr;
+    for (; current < end; ++current) {
+      int64_t uncompressed_idx = indices[current];
+      if (uncompressed_idx < 0 || uncompressed_idx >= uncompressed_data_size) {
+        return false;
+      }
+      int64_t idx = compressed_indices_table[uncompressed_idx];
+      if (idx == -1) {
+        weights_addr++;
+        continue;
+      }
+
+      const uint8_t* input_row_base = input + fused_block_size * idx;
+      const uint8_t* scale_bias_addr = input_row_base + scale_bias_offset;
+
+      float scale =
+          cpu_half2float(*reinterpret_cast<const float16*>(scale_bias_addr));
+      float bias = cpu_half2float(
+          *reinterpret_cast<const float16*>(scale_bias_addr + sizeof(float16)));
+
+      if (weights != nullptr) {
+        float weight = *weights_addr++;
+        scale *= weight;
+        bias *= weight;
+      }
+
+      const uint8_t* input_row = input_row_base;
+      if (bit_rate == 4) {
+        int64_t j = 0;
+#ifdef FBGEMM_VECTOR_WIDTH
+        for (; j < block_size - (block_size % (FBGEMM_VECTOR_WIDTH * 2));
+             j += 2) {
+          uint8_t tmp = *input_row++;
+          float quantized1 = float(tmp & 0xf);
+          float quantized2 = float(tmp >> 4);
+          buf[j] = std::fma(scale, quantized1, buf[j] + bias);
+          buf[j + 1] = std::fma(scale, quantized2, buf[j + 1] + bias);
+        }
+#endif
+        for (; j < block_size; j += 2) {
+          uint8_t tmp = *input_row++;
+          float quantized1 = float(tmp & 0xf);
+          float quantized2 = float(tmp >> 4);
+          buf[j] = std::fma(scale, quantized1, buf[j] + bias);
+          buf[j + 1] = std::fma(scale, quantized2, buf[j + 1] + bias);
+        }
+      } else if (bit_rate == 2) {
+        int64_t j = 0;
+#ifdef FBGEMM_VECTOR_WIDTH
+        for (; j < block_size - (block_size % (FBGEMM_VECTOR_WIDTH * 4));
+             j += 4) {
+          uint8_t tmp = *input_row++;
+          float quantized1 = float(tmp & 0x3);
+          float quantized2 = float((tmp & 0xC) >> 2);
+          float quantized3 = float((tmp & 0x30) >> 4);
+          float quantized4 = float(tmp >> 6);
+          buf[j] = std::fma(scale, quantized1, buf[j] + bias);
+          buf[j + 1] = std::fma(scale, quantized2, buf[j + 1] + bias);
+          buf[j + 2] = std::fma(scale, quantized3, buf[j + 2] + bias);
+          buf[j + 3] = std::fma(scale, quantized4, buf[j + 3] + bias);
+        }
+#endif
+        for (; j < block_size; j += 4) {
+          uint8_t tmp = *input_row++;
+          float quantized1 = float(tmp & 0x3);
+          float quantized2 = float((tmp & 0xC) >> 2);
+          float quantized3 = float((tmp & 0x30) >> 4);
+          float quantized4 = float(tmp >> 6);
+          buf[j] = std::fma(scale, quantized1, buf[j] + bias);
+          buf[j + 1] = std::fma(scale, quantized2, buf[j + 1] + bias);
+          buf[j + 2] = std::fma(scale, quantized3, buf[j + 2] + bias);
+          buf[j + 3] = std::fma(scale, quantized4, buf[j + 3] + bias);
+        }
+      }
+    }
+    if (normalize_by_lengths && len) {
+      float scale = 1.f / len;
+      for (int j = 0; j < block_size; ++j) {
+        buf[j] *= scale;
+      }
+    }
+    buf += block_size;
+  }
+  return current == index_size;
+}
+
 /// @ingroup tbe-cpu-autovec
 ///
 /// Autovectorized version of method `EmbeddingSpMDM_ref` for FP32 weight type.
@@ -2153,6 +2281,96 @@ INSTANTIATE_SPMDM_INDEX_T(std::uint8_t)
 #undef INSTANTIATE_SPMDM_OUT_T
 #undef INSTANTIATE_SPMDM_BASE
 
+template <typename IndexType, typename OffsetType>
+typename EmbeddingSpMDMRowWiseSparseKernelSignature<
+    uint8_t,
+    IndexType,
+    OffsetType>::Type
+GenerateEmbeddingSpMDMNBitRowWiseSparse_autovec(
+    int bit_rate,
+    int64_t block_size,
+    bool has_weight,
+    bool normalize_by_lengths,
+    [[maybe_unused]] int prefetch,
+    bool is_weight_positional,
+    bool use_offsets) {
+  assert((bit_rate == 2 || bit_rate == 4) && "bit_rate must be 2 or 4");
+  using specialization_helper::fixed;
+  using specialization_helper::match;
+  using specialization_helper::specialize;
+  using specialization_helper::var;
+
+#define SPECIALIZE(                                                 \
+    BIT_RATE,                                                       \
+    BLOCK_SIZE,                                                     \
+    HAS_WEIGHT,                                                     \
+    NORMALIZE_BY_LENGTHS,                                           \
+    IS_WEIGHT_POSITIONAL,                                           \
+    USE_OFFSETS)                                                    \
+  if (match(BIT_RATE, bit_rate) && match(BLOCK_SIZE, block_size) && \
+      match(HAS_WEIGHT, has_weight) &&                              \
+      match(NORMALIZE_BY_LENGTHS, normalize_by_lengths) &&          \
+      match(IS_WEIGHT_POSITIONAL, is_weight_positional) &&          \
+      match(USE_OFFSETS, use_offsets)) {                            \
+    return [=](int64_t output_size,                                 \
+               int64_t index_size,                                  \
+               int64_t uncompressed_data_size,                      \
+               const uint8_t* input,                                \
+               const IndexType* indices,                            \
+               const OffsetType* offsets_or_lengths,                \
+               const float* weights,                                \
+               float* out,                                          \
+               const int32_t* compressed_indices_table) {           \
+      if (specialize(HAS_WEIGHT, has_weight)) {                     \
+        __builtin_assume(weights != nullptr);                       \
+      } else {                                                      \
+        weights = nullptr;                                          \
+      }                                                             \
+      return EmbeddingSpMDMNBitRowWiseSparse_autovec(               \
+          /*bit_rate=*/specialize(BIT_RATE, bit_rate),              \
+          /*block_size=*/specialize(BLOCK_SIZE, block_size),        \
+          /*output_size=*/output_size,                              \
+          /*index_size=*/index_size,                                \
+          /*uncompressed_data_size=*/uncompressed_data_size,        \
+          /*input=*/input,                                          \
+          /*indices=*/indices,                                      \
+          /*compressed_indices_table=*/compressed_indices_table,    \
+          /*offsets_or_lengths=*/offsets_or_lengths,                \
+          /*weights=*/weights, /*normalize_by_lengths=*/            \
+          specialize(NORMALIZE_BY_LENGTHS, normalize_by_lengths),   \
+          /*out=*/out, /*is_weight_positional=*/                    \
+          specialize(IS_WEIGHT_POSITIONAL, is_weight_positional),   \
+          /*use_offsets=*/specialize(USE_OFFSETS, use_offsets));    \
+    };                                                              \
+  }
+
+  SPECIALIZE(/*BIT_RATE*/ fixed(4), var, var, var, var, var);
+  SPECIALIZE(/*BIT_RATE*/ fixed(2), var, var, var, var, var);
+  abort(); // should not get here
+#undef SPECIALIZE
+}
+
+#define INSTANTIATE_SPMDM_NBIT_ROWWISE_SPARSE(INDEX_TYPE, OFFSET_TYPE)      \
+  template typename EmbeddingSpMDMRowWiseSparseKernelSignature<             \
+      uint8_t,                                                              \
+      INDEX_TYPE,                                                           \
+      OFFSET_TYPE>::Type                                                    \
+  GenerateEmbeddingSpMDMNBitRowWiseSparse_autovec<INDEX_TYPE, OFFSET_TYPE>( \
+      int bit_rate,                                                         \
+      int64_t block_size,                                                   \
+      bool has_weight,                                                      \
+      bool normalize_by_lengths,                                            \
+      int prefetch,                                                         \
+      bool is_weight_positional,                                            \
+      bool use_offsets);
+
+INSTANTIATE_SPMDM_NBIT_ROWWISE_SPARSE(int32_t, int32_t)
+INSTANTIATE_SPMDM_NBIT_ROWWISE_SPARSE(int32_t, int64_t)
+INSTANTIATE_SPMDM_NBIT_ROWWISE_SPARSE(int64_t, int32_t)
+INSTANTIATE_SPMDM_NBIT_ROWWISE_SPARSE(int64_t, int64_t)
+
+#undef INSTANTIATE_SPMDM_NBIT_ROWWISE_SPARSE
+
 } // namespace fbgemm
 
 #endif // #ifdef __linux__

src/EmbeddingSpMDMAutovec.h

@@ -92,6 +92,20 @@ GenerateEmbeddingSpMDMRowWiseSparse_autovec(
     bool is_weight_positional,
     bool use_offsets);
 
+template <typename IndexType, typename OffsetType>
+typename EmbeddingSpMDMRowWiseSparseKernelSignature<
+    uint8_t,
+    IndexType,
+    OffsetType>::Type
+GenerateEmbeddingSpMDMNBitRowWiseSparse_autovec(
+    int bit_rate,
+    int64_t block_size,
+    bool has_weight,
+    bool normalize_by_lengths,
+    int prefetch,
+    bool is_weight_positional,
+    bool use_offsets);
+
 } // namespace fbgemm
 
 #endif // #ifdef __linux__

src/EmbeddingSpMDMNBit.cc

@@ -1296,6 +1296,25 @@ GenerateEmbeddingSpMDMNBitRowWiseSparse(
   }
 #endif // CPUINFO_ARCH_X86 || CPUINFO_ARCH_X86_64
 
+#ifdef FBGEMM_AUTOVEC_AVAILABLE
+  if (!cpuinfo_initialize()) {
+    throw std::runtime_error("Failed to initialize cpuinfo!");
+  }
+  if ((fbgemmHasArmSve2Support() && !is_autovec_disabled()) ||
+      is_autovec_forced()) {
+    return GenerateEmbeddingSpMDMNBitRowWiseSparse_autovec<
+        /*IndexType=*/indxType,
+        /*OffsetType=*/offsetType>(
+        /*bit_rate=*/bit_rate,
+        /*block_size=*/block_size,
+        /*has_weight=*/has_weight,
+        /*normalize_by_lengths=*/normalize_by_lengths,
+        /*prefetch=*/prefetch,
+        /*is_weight_positional=*/is_weight_positional,
+        /*use_offsets=*/use_offsets);
+  }
+#endif
+
 #ifdef VLOG
   VLOG(0) << "AVX2 or AVX512 not found, taking the slow path";
 #endif