LiGR layers

CHANGELOG.md

@@ -5,6 +5,11 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## Unreleased
+
+### Added
+- LiGR transformer layers from "From Features to Transformers: Redefining Ranking for Scalable Impact" ([#295](https://github.com/MobileTeleSystems/RecTools/pull/295))
+
 ## [0.16.0] - 27.07.2025
 
 ### Added

README.md

@@ -33,6 +33,15 @@ faster than ever before.
 - In [HSTU tutorial](examples/tutorials/transformers_HSTU_tutorial.ipynb) we show that original metrics reported for HSTU on public Movielens datasets may actually be **underestimated**
 - Configurable, customizable, callback-friendly, checkpoints-included, logs-out-of-the-box, custom-validation-ready, multi-gpu-compatible! See  [Transformers Advanced Training User Guide](examples/tutorials/transformers_advanced_training_guide.ipynb) and [Transformers Customization Guide](examples/tutorials/transformers_customization_guide.ipynb)
 
+
+## ✨ Highlights: RecTools framework at ACM RecSys'25 ✨
+
+**RecTools implementations are featured in ACM RecSys'25: ["eSASRec: Enhancing Transformer-based Recommendations in a Modular Fashion"](https://www.arxiv.org/abs/2508.06450):**
+- The article presents a systematic benchmark of Transformer modifications using RecTools models. It offers a detailed evaluation of training objectives, Transformer architectures, loss functions, and negative sampling strategies in realistic, production-like settings
+- We introduce a new SOTA baseline, **eSASRec**, which combines SASRec’s training objective with LiGR Transformer layers and Sampled Softmax loss, forming a simple yet powerful recipe
+- **eSASRec** shows 23% boost over SOTA models, such as ActionPiece, on academic benchmarks
+- [LiGR](https://arxiv.org/pdf/2502.03417) Transformer layers used in **eSASRec** are now in RecTools
+
 Plase note that we always compare the quality of our implementations to academic papers results. [Public benchmarks for transformer models SASRec and BERT4Rec](https://github.com/blondered/bert4rec_repro?tab=readme-ov-file#rectools-transformers-benchmark-results) show that RecTools implementations achieve highest scores on multiple datasets compared to other published results.
 
 
@@ -107,7 +116,7 @@ The table below lists recommender models that are available in RecTools.
 | Model               | Type | Description (🎏 for user/item features, 🔆 for warm inference, ❄️ for cold inference support)                                                                               | Tutorials & Benchmarks |
 |---------------------|----|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------|--------|
 | HSTU                | Neural Network | `rectools.models.HSTUModel` - Sequential model with unidirectional pointwise aggregated attention mechanism, incorporating relative attention bias from positional and temporal information, introduced in ["Actions speak louder then words..."](https://arxiv.org/pdf/2402.17152), combined with "Shifted Sequence" training objective as in original public benchmarks<br>🎏                                    | 📓 [HSTU Theory & Practice](examples/tutorials/transformers_HSTU_tutorial.ipynb) <br>  📕 [Transformers Theory & Practice](examples/tutorials/transformers_tutorial.ipynb)<br>  📗 [Advanced training guide](examples/tutorials/transformers_advanced_training_guide.ipynb) <br> 🚀 [Top performance on public datasets](examples/tutorials/transformers_HSTU_tutorial.ipynb)
-| SASRec              | Neural Network | `rectools.models.SASRecModel` - Transformer-based sequential model with unidirectional attention mechanism and "Shifted Sequence" training objective <br>🎏                 | 📕 [Transformers Theory & Practice](examples/tutorials/transformers_tutorial.ipynb)<br>  📗 [Advanced training guide](examples/tutorials/transformers_advanced_training_guide.ipynb) <br>  📘 [Customization guide](examples/tutorials/transformers_customization_guide.ipynb) <br> 🚀 [Top performance on public benchmarks](https://github.com/blondered/bert4rec_repro?tab=readme-ov-file#rectools-transformers-benchmark-results) |
+| SASRec              | Neural Network | `rectools.models.SASRecModel` - Transformer-based sequential model with unidirectional attention mechanism and "Shifted Sequence" training objective. <br> For eSASRec variant specify `rectools.models.nn.transformers.ligr.LiGRLayers` for `transformer_layers_type` and `sampled_softmax` for `loss` <br>🎏                 | 📕 [Transformers Theory & Practice](examples/tutorials/transformers_tutorial.ipynb)<br>  📗 [Advanced training guide](examples/tutorials/transformers_advanced_training_guide.ipynb) <br>  📘 [Customization guide](examples/tutorials/transformers_customization_guide.ipynb) <br> 🚀 [Top performance on public benchmarks](https://github.com/blondered/bert4rec_repro?tab=readme-ov-file#rectools-transformers-benchmark-results) |
 | BERT4Rec            | Neural Network | `rectools.models.BERT4RecModel` - Transformer-based sequential model with bidirectional attention mechanism and "MLM" (masked item) training objective <br>🎏               | 📕 [Transformers Theory & Practice](examples/tutorials/transformers_tutorial.ipynb)<br>  📗 [Advanced training guide](examples/tutorials/transformers_advanced_training_guide.ipynb) <br>  📘 [Customization guide](examples/tutorials/transformers_customization_guide.ipynb) <br> 🚀 [Top performance on public benchmarks](https://github.com/blondered/bert4rec_repro?tab=readme-ov-file#rectools-transformers-benchmark-results) |
 | [implicit](https://github.com/benfred/implicit) ALS Wrapper | Matrix Factorization | `rectools.models.ImplicitALSWrapperModel` - Alternating Least Squares Matrix Factorizattion algorithm for implicit feedback. <br>🎏                                         | 📙 [Theory & Practice](https://rectools.readthedocs.io/en/latest/examples/tutorials/baselines_extended_tutorial.html#Implicit-ALS)<br> 🚀 [50% boost to metrics with user & item features](examples/5_benchmark_iALS_with_features.ipynb) |
 | [implicit](https://github.com/benfred/implicit) BPR-MF Wrapper | Matrix Factorization | `rectools.models.ImplicitBPRWrapperModel` - Bayesian Personalized Ranking Matrix Factorization algorithm.                                                                   | 📙 [Theory & Practice](https://rectools.readthedocs.io/en/latest/examples/tutorials/baselines_extended_tutorial.html#Bayesian-Personalized-Ranking-Matrix-Factorization-(BPR-MF)) |

rectools/models/nn/transformers/ligr.py

@@ -0,0 +1,177 @@
+import typing as tp
+
+import torch
+from torch import nn
+
+from rectools.models.nn.transformers.net_blocks import TransformerLayersBase
+
+from .net_blocks import init_feed_forward
+
+
+class LiGRLayer(nn.Module):
+    """
+    Transformer Layer as described in "From Features to Transformers:
+    Redefining Ranking for Scalable Impact" https://arxiv.org/pdf/2502.03417
+
+    Parameters
+    ----------
+    n_factors: int
+        Latent embeddings size.
+    n_heads: int
+        Number of attention heads.
+    dropout_rate: float
+        Probability of a hidden unit to be zeroed.
+    ff_factors_multiplier: int, default 4
+        Feed-forward layers latent embedding size multiplier.
+    bias_in_ff: bool, default ``False``
+        Add bias in Linear layers of Feed Forward
+    ff_activation: {"swiglu", "relu", "gelu"}, default "swiglu"
+        Activation function to use.
+    """
+
+    def __init__(
+        self,
+        n_factors: int,
+        n_heads: int,
+        dropout_rate: float,
+        ff_factors_multiplier: int = 4,
+        bias_in_ff: bool = False,
+        ff_activation: str = "swiglu",
+    ):
+        super().__init__()
+        self.multi_head_attn = nn.MultiheadAttention(n_factors, n_heads, dropout_rate, batch_first=True)
+        self.layer_norm_1 = nn.LayerNorm(n_factors)
+        self.dropout_1 = nn.Dropout(dropout_rate)
+        self.layer_norm_2 = nn.LayerNorm(n_factors)
+        self.feed_forward = init_feed_forward(n_factors, ff_factors_multiplier, dropout_rate, ff_activation, bias_in_ff)
+        self.dropout_2 = nn.Dropout(dropout_rate)
+
+        self.gating_linear_1 = nn.Linear(n_factors, n_factors)
+        self.gating_linear_2 = nn.Linear(n_factors, n_factors)
+
+    def forward(
+        self,
+        seqs: torch.Tensor,
+        attn_mask: tp.Optional[torch.Tensor],
+        key_padding_mask: tp.Optional[torch.Tensor],
+    ) -> torch.Tensor:
+        """
+        Forward pass through transformer block.
+
+        Parameters
+        ----------
+        seqs: torch.Tensor
+            User sequences of item embeddings.
+        attn_mask: torch.Tensor, optional
+            Optional mask to use in forward pass of multi-head attention as `attn_mask`.
+        key_padding_mask: torch.Tensor, optional
+            Optional mask to use in forward pass of multi-head attention as `key_padding_mask`.
+
+
+        Returns
+        -------
+        torch.Tensor
+            User sequences passed through transformer layers.
+        """
+        mha_input = self.layer_norm_1(seqs)
+        mha_output, _ = self.multi_head_attn(
+            mha_input,
+            mha_input,
+            mha_input,
+            attn_mask=attn_mask,
+            key_padding_mask=key_padding_mask,
+            need_weights=False,
+        )
+        gated_skip = torch.nn.functional.sigmoid(self.gating_linear_1(seqs))
+        seqs = seqs + torch.mul(gated_skip, self.dropout_1(mha_output))
+
+        ff_input = self.layer_norm_2(seqs)
+        ff_output = self.feed_forward(ff_input)
+        gated_skip = torch.nn.functional.sigmoid(self.gating_linear_2(seqs))
+        seqs = seqs + torch.mul(gated_skip, self.dropout_2(ff_output))
+        return seqs
+
+
+class LiGRLayers(TransformerLayersBase):
+    """
+    LiGR Transformer blocks.
+
+    Parameters
+    ----------
+    n_blocks: int
+        Number of transformer blocks.
+    n_factors: int
+        Latent embeddings size.
+    n_heads: int
+        Number of attention heads.
+    dropout_rate: float
+        Probability of a hidden unit to be zeroed.
+    ff_factors_multiplier: int, default 4
+        Feed-forward layers latent embedding size multiplier. Pass in ``transformer_layers_kwargs`` to override.
+    ff_activation: {"swiglu", "relu", "gelu"}, default "swiglu"
+        Activation function to use. Pass in ``transformer_layers_kwargs`` to override.
+    bias_in_ff: bool, default ``False``
+        Add bias in Linear layers of Feed Forward. Pass in ``transformer_layers_kwargs`` to override.
+    """
+
+    def __init__(
+        self,
+        n_blocks: int,
+        n_factors: int,
+        n_heads: int,
+        dropout_rate: float,
+        ff_factors_multiplier: int = 4,
+        ff_activation: str = "swiglu",
+        bias_in_ff: bool = False,
+    ):
+        super().__init__()
+        self.n_blocks = n_blocks
+        self.n_factors = n_factors
+        self.n_heads = n_heads
+        self.dropout_rate = dropout_rate
+        self.ff_factors_multiplier = ff_factors_multiplier
+        self.ff_activation = ff_activation
+        self.bias_in_ff = bias_in_ff
+        self.transformer_blocks = nn.ModuleList([self._init_transformer_block() for _ in range(self.n_blocks)])
+
+    def _init_transformer_block(self) -> nn.Module:
+        return LiGRLayer(
+            self.n_factors,
+            self.n_heads,
+            self.dropout_rate,
+            self.ff_factors_multiplier,
+            bias_in_ff=self.bias_in_ff,
+            ff_activation=self.ff_activation,
+        )
+
+    def forward(
+        self,
+        seqs: torch.Tensor,
+        timeline_mask: torch.Tensor,
+        attn_mask: tp.Optional[torch.Tensor],
+        key_padding_mask: tp.Optional[torch.Tensor],
+        **kwargs: tp.Any,
+    ) -> torch.Tensor:
+        """
+        Forward pass through transformer blocks.
+
+        Parameters
+        ----------
+        seqs: torch.Tensor
+            User sequences of item embeddings.
+        timeline_mask: torch.Tensor
+            Mask indicating padding elements.
+        attn_mask: torch.Tensor, optional
+            Optional mask to use in forward pass of multi-head attention as `attn_mask`.
+        key_padding_mask: torch.Tensor, optional
+            Optional mask to use in forward pass of multi-head attention as `key_padding_mask`.
+
+
+        Returns
+        -------
+        torch.Tensor
+            User sequences passed through transformer layers.
+        """
+        for block_idx in range(self.n_blocks):
+            seqs = self.transformer_blocks[block_idx](seqs, attn_mask, key_padding_mask)
+        return seqs

rectools/models/nn/transformers/net_blocks.py

@@ -33,14 +33,18 @@ class PointWiseFeedForward(nn.Module):
         Probability of a hidden unit to be zeroed.
     activation: torch.nn.Module
         Activation function module.
+    bias: bool, default ``True``
+        If ``True``, add bias to linear layers.
     """
 
-    def __init__(self, n_factors: int, n_factors_ff: int, dropout_rate: float, activation: torch.nn.Module) -> None:
+    def __init__(
+        self, n_factors: int, n_factors_ff: int, dropout_rate: float, activation: torch.nn.Module, bias: bool = True
+    ) -> None:
         super().__init__()
-        self.ff_linear_1 = nn.Linear(n_factors, n_factors_ff)
+        self.ff_linear_1 = nn.Linear(n_factors, n_factors_ff, bias)
         self.ff_dropout_1 = torch.nn.Dropout(dropout_rate)
         self.ff_activation = activation
-        self.ff_linear_2 = nn.Linear(n_factors_ff, n_factors)
+        self.ff_linear_2 = nn.Linear(n_factors_ff, n_factors, bias)
 
     def forward(self, seqs: torch.Tensor) -> torch.Tensor:
         """
@@ -61,6 +65,92 @@ def forward(self, seqs: torch.Tensor) -> torch.Tensor:
         return fin
 
 
+class SwigluFeedForward(nn.Module):
+    """
+    Feed-Forward network to introduce nonlinearity into the transformer model.
+    This implementation is based on FuXi and LLama SwigLU https://arxiv.org/pdf/2502.03036,
+    LiGR https://arxiv.org/pdf/2502.03417
+
+    Parameters
+    ----------
+    n_factors : int
+        Latent embeddings size.
+    n_factors_ff : int
+        How many hidden units to use in the network.
+    dropout_rate : float
+        Probability of a hidden unit to be zeroed.
+    bias: bool, default ``True``
+        If ``True``, add bias to linear layers.
+    """
+
+    def __init__(self, n_factors: int, n_factors_ff: int, dropout_rate: float, bias: bool = True) -> None:
+        super().__init__()
+        self.ff_linear_1 = nn.Linear(n_factors, n_factors_ff, bias=bias)
+        self.ff_dropout_1 = torch.nn.Dropout(dropout_rate)
+        self.ff_activation = torch.nn.SiLU()
+        self.ff_linear_2 = nn.Linear(n_factors_ff, n_factors, bias=bias)
+        self.ff_linear_3 = nn.Linear(n_factors, n_factors_ff, bias=bias)
+
+    def forward(self, seqs: torch.Tensor) -> torch.Tensor:
+        """
+        Forward pass.
+
+        Parameters
+        ----------
+        seqs : torch.Tensor
+            User sequences of item embeddings.
+
+        Returns
+        -------
+        torch.Tensor
+            User sequence that passed through all layers.
+        """
+        output = self.ff_activation(self.ff_linear_1(seqs)) * self.ff_linear_3(seqs)
+        fin = self.ff_linear_2(self.ff_dropout_1(output))
+        return fin
+
+
+def init_feed_forward(
+    n_factors: int, ff_factors_multiplier: int, dropout_rate: float, ff_activation: str, bias: bool = True
+) -> nn.Module:
+    """
+    Initialise Feed-Forward network with one of activation functions: "swiglu", "relu", "gelu".
+
+    Parameters
+    ----------
+    n_factors : int
+        Latent embeddings size.
+    ff_factors_multiplier : int
+        How many hidden units to use in the network.
+    dropout_rate : float
+        Probability of a hidden unit to be zeroed.
+    ff_activation : {"swiglu", "relu", "gelu"}
+        Activation function to use.
+    bias: bool, default ``True``
+        If ``True``, add bias to linear layers.
+
+    Returns
+    -------
+    nn.Module
+        Feed-Forward network.
+    """
+    if ff_activation == "swiglu":
+        return SwigluFeedForward(n_factors, n_factors * ff_factors_multiplier, dropout_rate, bias=bias)
+    if ff_activation == "gelu":
+        return PointWiseFeedForward(
+            n_factors, n_factors * ff_factors_multiplier, dropout_rate, activation=torch.nn.GELU(), bias=bias
+        )
+    if ff_activation == "relu":
+        return PointWiseFeedForward(
+            n_factors,
+            n_factors * ff_factors_multiplier,
+            dropout_rate,
+            activation=torch.nn.ReLU(),
+            bias=bias,
+        )
+    raise ValueError(f"Unsupported ff_activation: {ff_activation}")
+
+
 class TransformerLayersBase(nn.Module):
     """Base class for transformer layers."""