Exploring Different Types of Large Language Models (LLMs)
Exploring the Many Flavors of Large Language Models (LLMs)
The world of large language models (LLMs) has exploded with variety in the past few years. From super‑huge transformers powering ChatGPT and GPT‑4 to tiny on‑device models, there are many types of large language models each optimized for different goals. Rather than just rehash definitions, let’s dive into the deep differences between these flavors of LLMs — the “tech specs” that make each distinct. We’ll look at models quantized during training versus post-training quantization, sparse‐expert architectures, low‑rank adaptation methods, sparsely activated networks, edge‑optimized models, distilled/pruned models, instruction‑tuned and RLHF models, open vs closed models, and those built for very long context windows. In doing so we’ll name some concrete examples (from the Qwen3 series and beyond) and reference cutting-edge research.
The aim is to stay tech‑deep but conversational : imagine an informed reader who isn’t an LLM specialist but wants to really understand how modern LLMs differ under the hood. We’ll also weave in relevant tools and services (e.g. repo2txt for converting code to text, crawl4ai for data gathering, and the professional AI/ML development services that companies use to build these systems) where they fit naturally.
Quantized LLMs: Training vs Post-Training
A major trend in LLM engineering is quantization : reducing the precision of model weights (say from 16‑bit floats to 8‑bit integers or even 4‑bit). Quantized LLMs take up far less memory and can run much faster on hardware that supports low‑precision math. But there’s a big distinction between when quantization happens:
- Post-Training Quantization (PTQ): You first train a model in full precision, then after the fact convert its weights to lower precision. This is straightforward because you start with a working model and simply “round” its parameters to 8‑bit or 4‑bit. It’s easy and doesn’t require retraining, but it can slightly degrade accuracy because you lose information in the weights. In practice PTQ means compressing a trained model to run more efficiently.
- Quantization-Aware Training (QAT): From the start, the model is aware that weights will be low‑precision. During training you simulate quantization (or actually quantize) on-the-fly, so the optimizer learns to compensate for the reduced precision. QAT usually yields higher quality than PTQ, at the cost of a heavier training process. A popular example is QLoRA , which fine‑tunes an LLM in 4‑bit precision. Essentially, QAT integrates the weight‑quantization into the training loop so the final model performs better than one simply quantized after the fact.
In short, PTQ is like taking a finished product and shrinking it (easy but lossy), whereas QAT bakes in the size‑reduction during training (harder but retains accuracy). For instance, Meta researchers have shown that larger quantized models can outperform smaller high-precision models at equal inference cost: an 8‑bit quantized 13B model beat a 16‑bit 7B model.
Example: Consider an Llama‑2-7B model. In FP16 it’s ~14GB, but a 4‑bit quantized version might be only ~4GB. Even with 8‑bit, Llama‑2 shrinks dramatically. Qualcomm’s engineers have even demonstrated running Llama 2 on a smartphone by aggressively quantizing it, highlighting how far these techniques can go.
For readers interested in implementation, there are now many off‑the‑shelf quantized models (often marked GPTQ , NF4 or GGML on Hugging Face), and tools like huggingface/transformers support loading int8/int4 models. A well‑quantized LLM (especially large ones) can match or exceed its smaller full‑precision cousin in practice.
Sparse-Expert Models: Mixture-of-Experts (MoE)
Another big innovation is sparsely activated expert models , often called Mixture of Experts (MoE) . The core idea is to have not one giant monolithic network, but many “expert” subnetworks and a gating mechanism that decides which experts to use for each input token. In a MoE layer, each token of the input is routed to just a few experts out of many, so only a subset of the total parameters compute that token.
Imagine having 8 different specialist models (experts) and a router that picks the best one(s) for each snippet of text. Only those experts actually do the heavy lifting. This is similar to an ensemble but done dynamically inside the transformer.
Why MoE? It can give more capacity without linearly more computation. For example, Meta’s Llama 4 (Maverick) has 128 experts totalling 400B parameters, yet per token only ~17B parameters are active. In practice this means it can handle extremely long sequences (more on that later) and achieve high performance, yet each token only flows through a fraction of the model. It also allows parallelizing experts on different hardware to boost throughput. (Note: MoE is tricky to train and deploy – the routing can be hard to balance, and GPUs often expect dense math. But it’s a powerful scaling strategy.)
Examples: Google’s early Switch Transformer and GLaM were MoE models. More recently, Meta’s Llama4 uses MoE heavily (as above) for its long‑context variants. The Mistral Mixtral architecture is also essentially an 8‑expert MoE under the hood. The Qwen3 library includes both dense and MoE variants; for instance Qwen3-30B-A3B is a small MoE model that outperforms a similar-sized dense model (Qwen2.5-72B) “with 10× the activated parameters”. In other words, even a 30B MoE model can beat a 72B dense model by activating parts of it.
Trade-offs: The upside of Mixture-of-Experts is massive effective size and efficiency (since at inference time you only do a slice of the network per token). The downside is system complexity: it requires specialized implementation to route tokens and make GPUs share work. It also can require very large batches to keep all experts busy during training.
In practice you’ll see MoE models noted in their specs or tags – e.g.
mixture-of-experts
or
moe
. An MoE LLM might be tagged
Mixture-of-Experts LLM
. If you use Ollama’s tag system
(for
instance in the Qwen3 library), you’ll see dense vs MoE models separated. For example, the Qwen3 model
descriptions
highlight that it offers “dense and mixture-of-experts models”.
Beyond standard MoE – sparsely activated research: MoE is one way to limit active parameters , but research is pushing even further. Techniques like Q-Sparse and Turbo-Sparse make a model trainable so that only a few neurons ever fire . For instance, the recent Q-Sparse method introduces a straight‑through top‑k sparsification during training, so that each layer only activates a subset of units. The result is a model where most weights stay dormant in inference, dramatically cutting compute and memory. In principle, this lets a model behave like it has 10× the compute at inference: you build a network with many neurons but only use the “best” ones per context.
A helpful rule of thumb: sparse models (like MoE or Q-Sparse) achieve high capacity or long context handling by only activating parts of the network per input . For example, Llama4’s MoE shows only ~17B weights active per token out of 400B total. Similarly, Q-Sparse achieves nearly full-model accuracy while treating most activations as zeros. The catch is that training and routing become more involved, but the efficiency pay-off can be huge for inference.
Low-Rank Adaptation Models: LoRA and QLoRA
In many applications you don’t want to retrain or swap out an entire LLM – you just want to adapt it to a specific task or data. Low-Rank Adaptation (LoRA) is a clever trick for this. Instead of fine-tuning all the billions of parameters, LoRA injects a few small trainable matrices (of low rank) into the network while keeping the original weights frozen.
Put simply, LoRA freezes the big model and plugs in tiny “adapter” weights that capture task‑specific changes. Because these adapters are low‑rank, they add only a tiny fraction of parameters. The original LoRA paper showed that, compared to fully fine‑tuning GPT-3 (175B) with standard methods, LoRA could reduce trainable parameters by 10,000× and lower GPU memory needs by 3×, without losing performance . In other words, you fine‑tune almost nothing and get nearly the same results.
LoRA has become extremely popular for LLM fine-tuning because it’s so efficient. Many open-source fine-tuned models provide a LoRA adapter that you simply load on top of a base model. Importantly, LoRA adds no extra inference cost : the adapters combine with the main weights only at runtime, and are effectively “baked in.”
Examples:
“LoRA” is a key tag in model libraries. For example, the Qwen3/Mistral ecosystem has
LoRA‑fine‑tuned versions for specific tasks or dataset. You might see a model called
my-llm-lora-xxx
.
There’s also
QLoRA
, which is LoRA + 4-bit quantization used during fine-tuning
(quantization‑aware
LoRA). And an even newer variant is
QA-LoRA
(Quantization-Aware LoRA), which integrates 4-bit
quantization
during
the LoRA fine-tuning. QA-LoRA lets you fine-tune in low precision end-to-end,
producing
a quantized model without accuracy loss. In practice, using LoRA or QLoRA means you need to manage
only
megabytes of
adapter weights instead of gigabytes of full model weights.
When you come across a model labeled
“LoRA”
or
“Low-Rank Adapter”
, it means
it’s a
light‑fine‑tuned version of some base model. For example,
vicuna-13b-lora
would be Vicuna (which
itself
is LLaMA‑based) with LoRA adapters. These are in contrast to models labeled simply “fine-tuned,” which
often
implies
full fine-tuning of many parameters.
Sparsely-Activated Models: Limited Active Parameters
Closely related to MoE and Q-Sparse is the general concept of sparsely-activated models – models designed so that only a subset of parameters or activations are used at inference time . Aside from MoE (where only some experts are active), there are techniques to make even a regular transformer sparse in activation.
One way is through hard thresholding or top‑k gating : for each layer’s output, keep only the top-N values and zero out the rest. This was shown in Turbo-Sparse and similar work. Or you might have networks where each layer has many channels but the model learns which channels to enable. The goal is the same as MoE: you have a huge network with many weights, but for each input only a few weights contribute, saving compute.
In practical terms, a “sparsely activated” LLM can have billions of weights loaded, but maybe only use 10–20% each pass. The Llama4 example illustrates this: it has 400B weights but ~17B active per token (that’s ~4%). This gives an effective model size much bigger than the computation cost.
While research on extremely sparse activations is cutting-edge, the principle affects choices: if you want maximum capacity and speed, you might choose an MoE or “sparse” LLM. Frameworks and libraries are just beginning to support this, so many users don’t see it directly yet, but you might hear buzzwords like “sparsely-activated LLM” or “sparse transformer” in papers.
Edge-Optimized LLMs: Efficient Models for Mobile/Edge
With LLMs everywhere, there’s demand for models that can run on edge devices (phones, IoT, etc.) or just cheaply in general. These efficient LLMs for edge use tricks like extreme quantization, pruning, and very small architectures.
For on-device LLMs, the trend is tiny models (1–10B parameters or less) with heavy optimization. Google, for example, released Gemma models (2B and 7B) specifically for mobile; they are compressed versions of their Gemini lineup. An ODSC survey notes “TinyLlama and Gemma 2B are the best options for mobile and edge computing” . Mistral’s smaller 7B model is also often cited as a go-to for efficiency. Some companies even created bespoke minified LLMs (hypothetically, people talk about a “GPT‑4 Nano” or a “Llama 3 small variant” for phones).
Quantization for edge:
As mentioned, quantization is huge here. Qualcomm’s engineers famously
demonstrated running
Meta’s Llama 2
on a smartphone by quantizing and using their mobile NPUs. They ran
8‑bit (and even 4‑bit) LLMs like Stable Diffusion and Llama2 on-device, boosting speed and power
efficiency.
Libraries like Hugging Face’s
transformers
even include
model.int8()
functions to
automate
8-bit conversion. Tools like OnnxRuntime, TensorRT, CoreML, or TorchScript mobile builds help deploy
these
quantized
models in apps.
Specialized architectures: Beyond brute-force shrinking, some research rethinks the model design. For instance, Hyena is a convolutional-ish architecture that can replace some transformer blocks and handle long inputs with low memory; it’s noted for efficiency on edge-type hardware. Other efforts train models with integer arithmetic in mind. The key is fewer FLOPs and memory.
In practice, if you see an LLM marketed as
“for on-device”
or
“mobile/edge”
, it’s likely a
distilled or quantized model around 1–4B parameters. For example, an open‑source project
TinyLlama
is a 2B‑parameter LLM trimmed for phones, and Mistral has hinted at lightweight models. These models
typically
appear with tags like
mobile
or
tiny
.
Designing these is as much engineering as architecture. You often pair them with prompt engineering or retrieval to compensate for their smaller size. But when you hear “efficient LLMs for edge”, think small + quantized + fast.
Distilled and Pruned LLMs
Distillation and pruning are classic ways to shrink models, and they apply to LLMs too.
-
Knowledge Distillation: You use a big “teacher” model (say GPT-4 or PaLM) to generate outputs (answers, labels, logits) on some data, and train a smaller “student” model to mimic that behavior. Essentially the student learns the teacher’s knowledge . This often involves generating synthetic training data by querying the teacher. The result is a much smaller model that performs almost as well on the target tasks. In principle, you could distill GPT-4 into, say, a 3B student that can answer questions nearly as well on a defined domain.
Distillation is powerful because it captures the wisdom of a huge LLM in a compact form. A Snorkel AI guide summarizes: “LLMs are amazing, but they’re slow and expensive. Distillation lets data scientists build smaller models that are easier to host, cheaper to run, and much more responsive” . During distillation, the big LLM acts like an oracle labeling data, and the small model trains on that (often via cross-entropy to the teacher’s outputs).
Examples: Hugging Face offers many “distilled” models (e.g., DistilBERT, DistilGPT-2). Recently even models like LLaMA 2 have “student” versions distilled to e.g. 7B or 13B from 70B. If a model name includes “distilled” or “student”, that’s a clue.
-
Pruning: This is more fine-grained: you remove weights or even entire neurons from a pre-trained model. You might prune unimportant connections or heads, or cut out the last few layers (depth pruning) to make a smaller model. Pruning can be structured (remove whole rows/columns) or unstructured (zero out individual weights). For example, NVIDIA’s NeMo toolkit shows how one can drop layers or prune widths in a Llama fine-tuned model to go from 8B to 4B parameters. Pruning is often paired with fine-tuning or distillation afterward to recover any lost accuracy.
In practice, pruned models may be labeled as “pruned” in their tags, or simply released as smaller checkpoints. The OpenReview paper “Distillation in Practice” suggests combining structured pruning and distillation to get small language models (SLMs) that rival much larger ones.
Takeaway: Distilled/pruned LLMs trade capacity for efficiency. They are real models, just narrower or shorter. They require retraining (or fine‑tuning) after compression. You might see keywords like “distilled” or “pruned” in model descriptions. A well‑distilled 4B model might perform close to an 8B original on specific tasks, at a fraction of the cost.
Fine-Tuned, Instruction-Following, and RLHF LLMs
Many models out in the wild are labeled not by architecture but by their training style. Let’s clarify some terms: fine-tuned , instruction-following , and RLHF-based models.
-
Fine-tuned models: After pretraining on general text, these models are further trained (“fine-tuned”) on specific data. For example, one might take GPT-2 and fine-tune it on legal documents to make a legal assistant. Fine-tuning could be supervised (with input/output pairs) or something like “continual training” on a domain. Fine-tuning usually changes all or many parameters (unless using adapters like LoRA). The key is adaptation: the model is specialized beyond its general knowledge.
-
Instruction-following models (Instruction-tuned): These are fine-tuned on instruction-response data. Instead of random text, the model sees (prompt, response) pairs where the prompt is an instruction (e.g., “Explain how to tie a shoe”). The goal is to make a generally useful assistant that follows directions. InstructGPT (OpenAI’s first instruction-tuned GPT-3.5), Flan-T5, and other “Chat” variants fall into this category. They behave more helpfully out of the box on tasks given by users. Crucially, many open models like LLaMA-2-Chat or Vicuna are only instruction-tuned, not RLHF‑tuned. For example, Vicuna is basically LLaMA-7B or 13B trained on ChatGPT-style data, but no RL. It can follow many prompts but can still make mistakes or hallucinate because it lacks the preference fine-tuning.
-
RLHF-based models: RLHF stands for Reinforcement Learning from Human Feedback . This is a multi-step process used by ChatGPT, GPT-4, Claude, and others. The steps are: (1) start with a pretrained or instruction-tuned model, (2) collect human preference data (people rank or score example outputs), (3) train a reward model to predict those human scores, (4) use reinforcement learning (like PPO) to adjust the model so it maximizes the reward model. In short, the model learns to prefer answers humans like. The result is generally safer, more aligned behavior.
A Hugging Face blog explains RLHF as using human feedback as a loss to optimize the LLM, aligning it to human values. It was the “secret sauce” behind ChatGPT. Note that RLHF is expensive – it needs curated human data and complex training. Many open models do not use RLHF because of cost. The above blog on instruction tuning points out that “most open‑source models have not gone through the alignment stage (RLHF), due to (1) high cost, (2) difficulty tuning RL, and (3) lack of preference data”.
Implications: An instruction-tuned model (like a Vicuna or open‑source “chat” model) will follow prompts in a helpful tone, but may still confidently give wrong answers or fail on tricky queries. An RLHF-tuned model (ChatGPT, GPT-4, Claude) is typically more careful: it will often say “I don’t know” when unsure, follow user instructions safely, and avoid disallowed content. Both types are “fine‑tuned”, but RLHF adds that extra layer of human alignment.
When you see model tags or descriptions, look for words like “instruction-following”, “RLHF”, “chat”, or “aligned”. For instance, Llama-2-Chat or Anthropic’s Claude are explicitly RLHF-fine-tuned (closing gaps identified with human preference data), whereas something like Llama-2-Instruct or Flan-UL2 was tuned only with supervised instruction data. In practice, RLHF models often require a license or API (OpenAI/Anthropic), while instruction-tuned ones are often open to use locally.
Open vs Closed Models
A major non-technical distinction is open-source versus closed/proprietary LLMs. Open models (like LLaMA, Mistral, Mistral Mixtral, GPT‑Neo, etc.) have their weights or code freely available. Closed models (like GPT-4, Claude 3, Bard, Meta’s Llama 4 when not released, etc.) do not share internal details. This choice has big implications:
-
Customization and Innovation: Open LLMs allow anyone to inspect, modify, or fine-tune the model. Researchers can analyze their training data, discover biases, or add new capabilities. Companies can tailor them to niche use-cases. The Atelier report notes “Open-source is a clear frontrunner when it comes to cost and adaptability” . The LLaMA series (Meta’s academic release) and Mistral models spurred a wave of open innovation (Vicuna, Ouroboros, etc.).
-
Performance and Safety: Closed models are often more polished and may perform better “out of the box” for many tasks. For example, OpenAI and Anthropic pour tremendous resources into training and safety testing. But users must trust the provider’s claims – you can’t verify how a closed model was trained or what data it saw. L’Atelier points out that closed-source models are “run by companies that do not disclose their models, training data, or code, making independent inspection ... difficult”. If a closed model hallucinates or has a bias, you have little recourse except to hope the company fixes it.
-
Ethical and Security Concerns: Open models might make it easier for “misaligned” uses, since anyone can use them without guardrails. Conversely, closed models keep control in the hands of the provider (e.g. OpenAI’s content filters). The Atelier analysis warns that open-source LLMs are more likely to be scrutinized by researchers , which helps catch biases, but their availability also makes it easier for malicious actors to exploit weaknesses . It’s a double-edged sword.
In practice, whether an LLM is open or closed affects how organizations can use it. Open models (Meta Llama, Mistral, etc.) can be downloaded and run on your own machines; you can even link them with tools like repo2txt or crawl4ai for custom pipelines. Closed models (GPT-4, Claude) usually require API calls and often subscription fees. The trade-offs include cost, flexibility, and trust. As the Atelier piece puts it, “The choice... depends on factors like budget, requirements, and desired level of customization and integration”.
Examples:
In the wild you’ll often see tags like
open-source
or model names like
“Llama2-7B” (open weights) versus proprietary names like “GPT-4” (closed). It’s also common to mention
license:
Llama2 has a permissive license, while GPT-4’s details are secret.
Long-Context LLMs and Extended Architecture
Finally, let’s talk about long-context models. Traditional transformers have a fixed “context window” (e.g. 1024 or 2048 tokens) beyond which they can’t attend. But many tasks benefit from very long contexts – whole books, codebases, or multi‑hour transcripts. A new breed of LLMs tackles this with special architecture and training.
A model’s context window is essentially its working memory in one session. GPT-3 was around 2048 tokens; GPT-4 Turbo and Anthropic Claude 3 boast 128k and 150k token windows respectively. New open models claim tens or hundreds of thousands of tokens. But how do they pull this off, since vanilla attention is O(n²)?
-
Efficient Attention Tricks: Techniques like sparse attention , local attention (only attend to nearby tokens), linearized attention (Performer, Linformer), or sliding windows (Longformer, BigBird) reduce the cost. Some models use hierarchical or dilated attention to scale. These strategies let a model process longer sequences by ignoring some token pairs.
-
Segmented Memory & Reversible Layers: Approaches like Transformer-XL add recurrence or caching so that old contexts carry forward. Some models break long text into chunks and summarize them. For example, Google’s Recurrent Memory Transformer and DeepMind’s RETRO use chunking and retrieval to extend memory. Newer methods like Hyena use convolutional approximations for subquadratic scaling.
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Mixing with MoE: Interestingly, MoE also helps with long context. The Llama4 architecture uses experts to scale context – for instance, its “Scout” variant supports 10 million token context by using MoE routing. The idea is that instead of one model handling 1M tokens at once, multiple experts each handle parts of the sequence and pass summaries. As the long‑context survey notes, “instead of one giant attention covering 1M tokens... you have, say, 10 expert modules each comfortably handling 100k tokens and lightly communicating” . That approximates an ultra-long context with manageable cost.
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Huge Context Models in Practice: Recent models showcase these ideas. Meta’s Llama 2-Long was trained for 32k contexts (by RoPE interpolation and more layers). OpenAI’s GPT-4o (the next-gen model) reportedly goes to millions of tokens. Anthropic’s Redwood project experiments with hierarchical memory for truly long conversations.
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Retrieval Augmentation vs. Long Context: It’s worth noting that “long context” isn’t just for input. Many workflows use Retrieval-Augmented Generation (RAG) to handle large knowledge bases, feeding only the relevant parts into a short-context model. But long-context LLMs reduce the need for chunking: you can feed a whole book or code repository at once. In fact, a good strategy is hybrid: let an LLM with, say, 100k context ingest hundreds of pages, and fall back on retrieval for anything beyond that.
In summary, long-context window LLMs use architectural tweaks (sparse attention, memory, MoE, etc.) to blow past the token limit. If you see a model touting “64K” or “128K” or higher context, it’s using these tricks. Research even points out emerging “infinite context” models on the horizon. For users, this means some models can now process novels or large datasets in one go, which changes how we design prompts and pipelines.
Integrating LLMs: Tools and Services
Building on all these LLM types requires practical tools and know-how. For instance, if you want your LLM to understand a codebase, you might first convert that repo into text form. The tool repo2txt does exactly this: it converts GitHub code into plain text so an LLM can process it as input. There’s even an offline variant Repo2Txt local converter if you need to do this without internet. Similarly, if you need to gather fresh data from the web for an LLM, tools like crawl4ai automate web crawling and content extraction for AI.
On the deployment side, companies often rely on professional services to handle complex LLM pipelines. Experienced AI/ML development services can help integrate and fine-tune models, while full-stack web development and DevOps services ensure they run reliably at scale. In short, there’s a whole ecosystem of tools (for data preparation, model management, etc.) and IT expertise behind successful LLM projects. General IT services providers often bundle LLM consulting with cloud setup, security, and maintenance.
Conclusion
Large language models today come in many flavors , each tailored to a different goal. Some are quantized for efficiency, some use sparse experts or LoRA adapters for size/performance trade-offs, some are pruned or distilled to be lightweight, and others are fine‑tuned or RLHF‑aligned to behave usefully. There are even models built to run on your phone or to read a novel in one shot.
Understanding these distinctions helps technologists pick the right tool. If you need raw horsepower and don’t care about size, a huge dense model might do. If you need speed or to run on limited hardware, a quantized or distillated model is better. If you want an assistant that’s safe and aligned, look for instruction‑tuned + RLHF models. If you want to peek under the hood and tweak things, open-source LLMs are your playground, whereas closed models trade some openness for turnkey reliability.
In practice, it’s often a blend: you might take an open model, apply LoRA fine-tuning with quantization for edge deployment, and add retrieval or RAG for extra knowledge. The field is evolving fast – new techniques like QA-LoRA or Q-Sparse keep coming. One certainty is that the taxonomy of LLMs will keep growing. Whether you’re a researcher or just “tech-savvy,” the key is to focus on your needs (accuracy, cost, speed, context length, etc.) and pick the LLM type that matches.
At the end of the day, these are all just tools. The magic is in how you apply them. And remember: behind every powerful LLM is often a pile of infrastructure, from specialized libraries and converters to expert DevOps teams. Bringing one into production might involve AI/ML development services , careful full-stack web development to interface with it, and DevOps services to keep it running smoothly. So as you experiment with quantized models, mixtures of experts, LoRA adapters, or whatever the next breakthrough is, remember the ecosystem of tools and expertise that make it all possible.
Sources: We’ve drawn on industry write-ups and papers on LLM quantization, mixture-of-experts, LoRA, distillation, RLHF, and open-source LLM analysis, among others, to ensure we cover the latest technical insights. These combined perspectives paint a detailed picture of what makes each type of LLM fundamentally distinct.