Model Overview
Model Features
Model Capabilities
Use Cases
🚀 Independent Implementation of SPLADE++ Model (a.k.a splade-cocondenser* and family
) for the Industry setting.
This project is an independent implementation of the SPLADE++ model, with some efficiency tweaks tailored for the industry setting. It combines the strengths of lexical and semantic search by learning sparse representations, offering a balance between retrieval effectiveness and efficiency.
🚀 Quick Start
You can use this model with popular vector databases, the SPLADERunner
library, or HuggingFace. Refer to the "Usage" section below for detailed instructions.
✨ Features
- Balanced Retrieval: Strikes a fine balance between retrieval effectiveness and efficiency.
- Sparse Representations: Learns sparse representations for queries and documents, providing interpretability and implicit/explicit expansion mechanisms.
- Industry-Tailored: Minor retrieval efficiency tweaks make it more suitable for industry settings.
- Competitive Performance: Achieves competitive MRR@10 scores on both in-domain and out-of-domain data, with low retrieval latency on consumer-grade GPUs.
📦 Installation
To use the SPLADERunner
library, you can install it via pip
:
pip install spladerunner
💻 Usage Examples
Basic Usage
With SPLADERunner Library
from spladerunner import Expander
# Default model is the document expander.
expander = Expander()
# Sample Document expansion
sparse_rep = expander.expand(
["The Manhattan Project and its atomic bomb helped bring an end to World War II. Its legacy of peaceful uses of atomic energy continues to have an impact on history and science."])
With HuggingFace
import torch
from transformers import AutoModelForMaskedLM, AutoTokenizer
device = "cuda:0" if torch.cuda.is_available() else "cpu"
tokenizer = AutoTokenizer.from_pretrained('prithivida/Splade_PP_en_v1')
reverse_voc = {v: k for k, v in tokenizer.vocab.items()}
model = AutoModelForMaskedLM.from_pretrained('prithivida/Splade_PP_en_v1')
model.to(device)
sentence = """The Manhattan Project and its atomic bomb helped bring an end to World War II. Its legacy of peaceful uses of atomic energy continues to have an impact on history and science."""
inputs = tokenizer(sentence, return_tensors='pt')
inputs = {key: val.to(device) for key, val in inputs.items()}
input_ids = inputs['input_ids']
attention_mask = inputs['attention_mask']
outputs = model(**inputs)
logits, attention_mask = outputs.logits, attention_mask
relu_log = torch.log(1 + torch.relu(logits))
weighted_log = relu_log * attention_mask.unsqueeze(-1)
max_val, _ = torch.max(weighted_log, dim=1)
vector = max_val.squeeze()
cols = vect
Advanced Usage
- Using with Popular VectorDBs:
| VectorDB | Colab Link |
|----------|------------|
| Pinecone |
| | Qdrant | TBD |
📚 Documentation
1. What are Sparse Representations and Why learn one?
2. Semantic Search: Learned Neural / Dense retrievers (DPR, Sentence transformers*, BGE* models) with approximate nearest neighbors search has shown impressive results. Here are the pros and cons:
- ✅ Search how humans innately think.
- ✅ When finetuned beats sparse by long way.
- ✅ Easily works with Multiple modals.
- ❌ Suffers token amnesia (misses term matching),
- ❌ Resource intensive (both index & retreival),
- ❌ Famously hard to interpret.
- ❌ Needs fine-tuning for OOD data.
3. The big idea: Getting pros of both searches made sense and that gave rise to interest in learning sparse representations for queries and documents with some interpretability. The sparse representations also double as implicit or explicit (latent, contextualized) expansion mechanisms for both query and documents. If you are new to query expansion learn more here from the master himself Daniel Tunkelang.
4. What a Sparse model learns ? The model learns to project it's learned dense representations over a MLM head to give a vocabulary distribution. Which is just to say the model can do automatic token expansion. (Image courtesy of pinecone)

2. Motivation
SPLADE models are a fine balance between retrieval effectiveness (quality) and retrieval efficiency (latency and $). With that in mind, we did very minor retrieval efficiency tweaks to make it more suitable for an industry setting. (Pure MLE folks should not conflate efficiency to model inference efficiency. Our main focus is on retrieval efficiency. Hereinafter efficiency is a short hand for retrieval efficiency unless explicitly qualified otherwise. Not that inference efficiency is not important, we will address that subsequently.)
TL;DR of Our attempt & results
- FLOPS tuning: Separate Seq lens and Severely restrictive FLOPs schedule and token budget doc(128) & query(24) NOT 256 unlike Official SPLADE++. Inspired from SparseEmbed
- Init Weights: Middle Trained bert-base-uncased with MLM Loss. Some corpus awareness like Official splade++ / ColBERT
- Yet achieves competitive effectiveness of MRR@10 37.8 in ID data (& OOD 49.4) and a retrieval latency of - 48.81ms. (multi-threaded) all On Consumer grade-GPUs with only 5 negatives per query.
- For Industry setting: Effectiveness on custom domains needs more than just Trading FLOPS for tiny gains and The Premise "SPLADE++ are not well suited to mono-cpu retrieval" does not hold.
- Owing to query-time inference latency we still need 2 models one for query & doc, This is a Doc model and Query model will be released soon.

Note: The paper refers to the best performing models as SPLADE++, hence for consistency we are reusing the same.
3. Why FLOPS is one of the key metrics for industry setting?
So, by design "how to beat SoTA MRR?" was never our goal, Instead "At what cost can we achieve an acceptable effectiveness i.e. MRR@10". Non-chalantly reducing lambda values (λQ,λD, see above table) will achieve a better MRR. But Lower lambda values = Higher FLOPS = More tokens = Poorer efficiency. This is NOT desirable for an industry setting.
Ours
number of actual dimensions: 121
SPLADE BOW rep:
[('stress', 2.42), ('thermal', 2.31), ('glass', 2.27), ('pan', 1.78), ('heat', 1.66), ('glasses', 1.58), ('crack', 1.42), ('anxiety', 1.36), ('break', 1.31), ('window', 0.91), ('heating', 0.84), ('hot', 0.82), ('adjacent', 0.82), ('hotter', 0.82), ('if', 0.75), ('cause', 0.7), ('caused', 0.7), ('create', 0.7), ('factors', 0.69), ('created', 0.68), ('cracks', 0.67), ('breaks', 0.67), ('area', 0.66), ('##glass', 0.66), ('cracked', 0.63), ('areas', 0.6), ('cracking', 0.59), ('windows', 0.58), ('effect', 0.56), ('causes', 0.56), ('ruin', 0.54), ('severe', 0.54), ('too', 0.53), ('flame', 0.5), ('collapse', 0.49), ('stresses', 0.49), ('or', 0.48), ('physics', 0.47), ('temperature', 0.46), ('get', 0.46), ('heated', 0.45), ('problem', 0.45), ('energy', 0.44), ('hottest', 0.42), ('phenomenon', 0.42), ('sweating', 0.41), ('insulation', 0.39), ('level', 0.39), ('warm', 0.39), ('governed', 0.38), ('formation', 0.37), ('failure', 0.35), ('frank', 0.34), ('cooling', 0.32), ('fracture', 0.31), ('because', 0.31), ('crystal', 0.31), ('determined', 0.31), ('boiler', 0.31), ('mechanical', 0.3), ('shatter', 0.29), ('friction', 0.29), ('levels', 0.29), ('cold', 0.29), ('will', 0.29), ('ceramics', 0.29), ('factor', 0.28), ('crash', 0.28), ('reaction', 0.28), ('fatigue', 0.28), ('hazard', 0.27), ('##e', 0.26), ('anger', 0.26), ('bubble', 0.25), ('process', 0.24), ('cleaning', 0.23), ('surrounding', 0.22), ('theory', 0.22), ('sash', 0.22), ('distraction', 0.21), ('adjoining', 0.19), ('environmental', 0.19), ('ross', 0.18), ('formed', 0.17), ('broken', 0.16), ('affect', 0.16), ('##pan', 0.15), ('graphic', 0.14), ('damage', 0.14), ('bubbles', 0.13), ('windshield', 0.13), ('temporal', 0.13), ('roof', 0.12), ('strain', 0.12), ('clear', 0.09), ('ceramic', 0.08), ('stressed', 0.08), ('##uation', 0.08), ('cool', 0.08), ('expand', 0.07), ('storm', 0.07), ('shock', 0.07), ('psychological', 0.06), ('breaking', 0.06), ('##es', 0.06), ('melting', 0.05), ('burst', 0.05), ('sensing', 0.04), ('heats', 0.04), ('error', 0.03), ('weather', 0.03), ('drink', 0.03), ('fire', 0.03), ('vibration', 0.02), ('induced', 0.02), ('warmer', 0.02), ('leak', 0.02), ('fog', 0.02), ('safety', 0.01), ('surface', 0.01), ('##thermal', 0.0)]
naver/splade-cocondenser-ensembledistil (SoTA, ~4% more tokens + FLOPS = 1.85)
number of actual dimensions: 126
SPLADE BOW rep:
[('stress', 2.25), ('glass', 2.23), ('thermal', 2.18), ('glasses', 1.65), ('pan', 1.62), ('heat', 1.56), ('stressed', 1.42), ('crack', 1.31), ('break', 1.12), ('cracked', 1.1), ('hot', 0.93), ('created', 0.9), ('factors', 0.81), ('broken', 0.73), ('caused', 0.71), ('too', 0.71), ('damage', 0.69), ('if', 0.68), ('hotter', 0.65), ('governed', 0.61), ('heating', 0.59), ('temperature', 0.59), ('adjacent', 0.59), ('cause', 0.58), ('effect', 0.57), ('fracture', 0.56), ('bradford', 0.55), ('strain', 0.53), ('hammer', 0.51), ('brian', 0.48), ('error', 0.47), ('windows', 0.45), ('will', 0.45), ('reaction', 0.42), ('create', 0.42), ('windshield', 0.41), ('heated', 0.41), ('factor', 0.4), ('cracking', 0.39), ('failure', 0.38), ('mechanical', 0.38), ('when', 0.38), ('formed', 0.38), ('bolt', 0.38), ('mechanism', 0.37), ('warm', 0.37), ('areas', 0.36), ('area', 0.36), ('energy', 0.34), ('disorder', 0.33), ('barry', 0.33), ('shock', 0.32), ('determined', 0.32), ('gage', 0.32), ('sash', 0.31), ('theory', 0.31), ('level', 0.31), ('resistant', 0.31), ('brake', 0.3), ('window', 0.3), ('crash', 0.3), ('hazard', 0.29), ('##ink', 0.27), ('ceramic', 0.27), ('storm', 0.25), ('problem', 0.25), ('issue', 0.24), ('impact', 0.24), ('fridge', 0.24), ('injury', 0.23), ('ross', 0.22), ('causes', 0.22), ('affect', 0.21), ('pressure', 0.21), ('fatigue', 0.21), ('leak', 0.21), ('eye', 0.2), ('frank', 0.2), ('cool', 0.2), ('might', 0.19), ('gravity', 0.18), ('ray', 0.18), ('static', 0.18), ('collapse', 0.18), ('physics', 0.18), ('wave', 0.18), ('reflection', 0.17), ('parker', 0.17), ('strike', 0.17), ('hottest', 0.17), ('burst', 0.16), ('chance', 0.16), ('burn', 0.14), ('rubbing', 0.14), ('interference', 0.14), ('bailey', 0.13), ('vibration', 0.12), ('gilbert', 0.12), ('produced', 0.12), ('rock', 0.12), ('warmer', 0.11), ('get', 0.11), ('drink', 0.11), ('fireplace', 0.11), ('ruin', 0.1), ('brittle', 0.1), ('fragment', 0.1), ('stumble', 0.09), ('formation', 0.09), ('shatter', 0.08), ('great', 0.08), ('friction', 0.08), ('flash', 0.07), ('cracks', 0.07), ('levels', 0.07), ('smash', 0.04), ('fail', 0.04), ('fra', 0.04), ('##glass', 0.03), ('variables', 0.03), ('because', 0.02), ('knock', 0.02), ('sun', 0.02), ('crush', 0.01), ('##e', 0.01), ('anger', 0.01)]
naver/splade-v2-distil (~48% more tokens + FLOPS = 3.82)
number of actual dimensions: 234
SPLADE BOW rep:
[('glass', 2.55), ('stress', 2.39), ('thermal', 2.38), ('glasses', 1.95), ('stressed', 1.87), ('crack', 1.84), ('cool', 1.78), ('heat', 1.62), ('pan', 1.6), ('break', 1.53), ('adjacent', 1.44), ('hotter', 1.43), ('strain', 1.21), ('area', 1.16), ('adjoining', 1.14), ('heated', 1.11), ('window', 1.07), ('stresses', 1.04), ('hot', 1.03), ('created', 1.03), ('create', 1.03), ('cause', 1.02), ('factors', 1.02), ('cooler', 1.01), ('broken', 1.0), ('too', 0.99), ('fracture', 0.96), ('collapse', 0.96), ('cracking', 0.95), ('great', 0.93), ('happen', 0.93), ('windows', 0.89), ('broke', 0.87), ('##e', 0.87), ('pressure', 0.84), ('hottest', 0.84), ('breaking', 0.83), ('govern', 0.79), ('shatter', 0.76), ('level', 0.75), ('heating', 0.69), ('temperature', 0.69), ('cracked', 0.69), ('panel', 0.68), ('##glass', 0.68), ('ceramic', 0.67), ('sash', 0.66), ('warm', 0.66), ('areas', 0.64), ('creating', 0.63), ('will', 0.62), ('tension', 0.61), ('cracks', 0.61), ('optical', 0.6), ('mechanism', 0.58), ('kelly', 0.58), ('determined', 0.58), ('generate', 0.58), ('causes', 0.56), ('if', 0.56), ('factor', 0.56), ('the', 0.56), ('chemical', 0.55), ('governed', 0.55), ('crystal', 0.55), ('strike', 0.55), ('microsoft', 0.54), ('creates', 0.53), ('than', 0.53), ('relation', 0.53), ('glazed', 0.52), ('compression', 0.51), ('painting', 0.51), ('governing', 0.5), ('harden', 0.49), ('solar', 0.48), ('reflection', 0.48), ('ic', 0.46), ('split', 0.45), ('mirror', 0.44), ('damage', 0.43), ('ring', 0.42), ('formation', 0.42), ('wall', 0.41), ('burst', 0.4), ('radiant', 0.4), ('determine', 0.4), ('one', 0.4), ('plastic', 0.39), ('furnace', 0.39), ('difference', 0.39), ('melt', 0.39), ('get', 0.39), ('contract', 0.38), ('forces', 0.38), ('gets', 0.38), ('produce', 0.38), ('surrounding', 0.37), ('vibration', 0.37), ('tile', 0.37), ('fail', 0.36), ('warmer', 0.36), ('rock', 0.35), ('fault', 0.35), ('roof', 0.34), ('burned', 0.34), ('physics', 0.33), ('welding', 0.33), ('why', 0.33), ('a', 0.32), ('pop', 0.32), ('and', 0.31), ('fra', 0.3), ('stat', 0.3), ('withstand', 0.3), ('sunglasses', 0.3), ('material', 0.29), ('ice', 0.29), ('generated', 0.29), ('matter', 0.29), ('frame', 0.28), ('elements', 0.28), ('then', 0.28), ('.', 0.28), ('pont', 0.28), ('blow', 0.28), ('snap', 0.27), ('metal', 0.26), ('effect', 0.26), ('reaction', 0.26), ('related', 0.25), ('aluminium', 0.25), ('neighboring', 0.25), ('weight', 0.25), ('steel', 0.25), ('bulb', 0.25), ('tear', 0.25), ('coating', 0.25), ('plumbing', 0.25), ('co', 0.25), ('microwave', 0.24), ('formed', 0.24), ('pipe', 0.23), ('drink', 0.23), ('chemistry', 0.23), ('energy', 0.22), ('reflect', 0.22), ('dynamic', 0.22), ('leak', 0.22), ('is', 0.22), ('lens', 0.21), ('frost', 0.21), ('lenses', 0.21), ('produced', 0.21), ('induced', 0.2), ('arise', 0.2), ('plate', 0.2), ('equations', 0.19), ('affect', 0.19), ('tired', 0.19), ('mirrors', 0.18), ('thickness', 0.18), ('bending', 0.18), ('cabinet', 0.17), ('apart', 0.17), ('##thermal', 0.17), ('gas', 0.17), ('equation', 0.17), ('relationship', 0.17), ('composition', 0.17), ('engineering', 0.17), ('block', 0.16), ('breaks', 0.16), ('when', 0.16), ('definition', 0.16), ('collapsed', 0.16), ('generation', 0.16), (',', 0.16), ('philips', 0.16), ('later', 0.15), ('wood', 0.15), ('neighbouring', 0.15), ('structural', 0.14), ('regulate', 0.14), ('neighbors', 0.13), ('lighting', 0.13), ('happens', 0.13), ('more', 0.13), ('property', 0.13), ('cooling', 0.12), ('shattering', 0.12), ('melting', 0.12), ('how', 0.11), ('cloud', 0.11), ('barriers', 0.11), ('lam', 0.11), ('conditions', 0.11), ('rule', 0.1), ('insulation', 0.1), ('bathroom', 0.09), ('convection', 0.09), ('cavity', 0.09), ('source', 0.08), ('properties', 0.08), ('bend', 0.08), ('bottles', 0.08), ('ceramics', 0.07), ('temper', 0.07), ('tense', 0.07), ('keller', 0.07), ('breakdown', 0.07), ('concrete', 0.07), ('simon', 0.07), ('solids', 0.06), ('windshield', 0.05), ('eye', 0.05), ('sunlight', 0.05), ('brittle', 0.03), ('caused', 0.03), ('suns', 0.03), ('floor', 0.02), ('components', 0.02), ('photo', 0.02), ('change', 0.02), ('sun', 0.01), ('crystals', 0.01), ('problem', 0.01), ('##proof', 0.01), ('parameters', 0.01), ('gases', 0.0), ('prism', 0.0), ('doing', 0.0), ('lattice', 0.0), ('ground', 0.0)]
- Note 1: This specific passage was used as an example for ease of comparison
4. How does it translate into Empirical metrics?
Our models are token sparse and yet effective. It translates to faster retrieval (User experience) and smaller index size ($). Mean retrieval time on the standard MS-MARCO small dev set and Scaled total FLOPS loss are the respective metrics are below. This is why Google's SparseEmbed is interesting as they also achieve SPLADE quality retrieval effectiveness with much lower FLOPs. Compared to ColBERT, SPLADE and SparseEmbed match query and document terms with a linear complexity as ColBERT’s late interaction i.e. all query-document term pairs takes a quadratic complexity. The Challenge with SparseEmbed is it uses a hyperparameter called Top-k to restrict number of tokens used to learn contextual dense representations. Say 64 and 256 tokens for query and passage encoding. But it is unclear how well these hyperparameters are transferable to other domains or languages (where the notion of tokens changes a lot like our mother tongue Tamil which is Agglutinative in nature).

- BEIR ZST OOD performance: Will be added to the end of page.
Our model is different in few more aspects
- Cocondenser Weights: Unlike the best Official SPLADE++ or SparseEmbed we do NOT initialse weights from Luyu/co-condenser* models. Yet we achieve CoCondenser SPLADE level performance. More on this later.
- Same size models: Official SPLADE++, SparseEmbed and Ours all finetune on the same size based model. Size of
bert-base-uncased
.
5. Roadmap and future directions for Industry Suitability
- Improve efficiency: This is a bottomless pit. We will continue to improve serving and retrieval efficiency.
- Custom/Domain Finetuning: OOD Zeroshot performance of SPLADE models is great but unimportant in the industry setting as we need the ability to finetune on custom datasets or domains. Finetuning SPLADE on a new dataset is not cheap and needs labelling of queries and passages. So we will continue to see how we can enable economically finetuning our recipe on custom datasets without expensive labelling.
- Multilingual SPLADE: Training cost of SPLADE i.e (GPU budget) directly proportional to Vocab size of the base model. So Mulitlingual SPLADE either using mbert or XLMR can be expensive as they have 120K and 250K vocab as opposed to 30K as in bert-base-uncased. We will continue to research to see how best we can extend our recipe to the multilingual world.
🔧 Technical Details
- FLOPS tuning: Separate sequence lengths and a severely restrictive FLOPs schedule and token budget (doc: 128, query: 24) instead of 256 as in the official SPLADE++. Inspired by SparseEmbed.
- Initial Weights: Middle-trained bert-base-uncased with MLM Loss, similar to the corpus awareness of official splade++ and ColBERT.
📄 License
This project is licensed under the Apache-2.0 license.





