src/index.qmd

---
title: "Optimizing LLM Performance Using Triton"
format: 
  revealjs:
    theme: dark
    transition: slide
    slide-number: true
author: "Matej Sirovatka"
date: "2025-02-22"
---

## `whoami`

- My name is Matej
- I'm a Master's student at Brno University of Technology
- I'm currently working on distributed training at Hugging Face 🤗

## `What is Triton?`

- open-source programming language for GPU kernels by Open AI
- Designed for AI/ML workloads
- Simplifies GPU programming compared to CUDA

![](media/optim_scale.png){.center fig-align="center"}

## `Why Optimize with Triton?`

- Simple yet effective
- Less headache than CUDA
- GPUs go `brrrrrrr` 🚀
- Feel cool when your kernel is faster than PyTorch 😎

## `Example Problem: KL Divergence`

- commonly used in LLMs for knowledge distillation
- for probability distributions $P$ and $Q$, the Kullback-Leibler divergence is defined as:

$$
D_{KL}(P \| Q) = \sum_{i} P_i \log\left(\frac{P_i}{Q_i}\right)
$$


```python
import torch
from torch.nn.functional import kl_div

def kl_div_torch(p: torch.Tensor, q: torch.Tensor) -> torch.Tensor:
    return kl_div(p, q)
```

## `How about Triton?`

```python
import triton
import triton.language as tl

@triton.jit
def kl_div_triton(
    p_ptr, q_ptr, output_ptr, n_elements, BLOCK_SIZE: tl.constexpr
):
    pid = tl.program_id(0)
    block_start = pid * BLOCK_SIZE
    offsets = block_start + tl.arange(0, BLOCK_SIZE)
    mask = offsets < n_elements
    
    p = tl.load(p_ptr + offsets, mask=mask)
    q = tl.load(q_ptr + offsets, mask=mask)
    
    output = p * (tl.log(p) - tl.log(q))
    tl.store(output_ptr + offsets, output, mask=mask)
```

## `How to integrate with PyTorch?`

- How to use our custom kernel with PyTorch autograd?

```python
import torch

class KlDiv(torch.autograd.Function):
    @staticmethod
    def forward(ctx, p, q):
        ctx.save_for_backward(q)
        output = torch.empty_like(p)
        grid = (len(p) + 512 - 1) // 512
        kl_div_triton[grid](p, q, output, len(p), BLOCK_SIZE=512)
        return output

    @staticmethod
    def backward(ctx, grad_output):
        q = ctx.saved_tensors[0]
        # Calculate gradients (another triton kernel)
        return ...
```

## `Some benchmarks`

- A KL Divergence kernel that is currently used in [Liger Kernel](https://github.com/linkedin/liger-kernel) written by @me

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![](media/kl_mem.png){.center fig-align="center"}

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![](media/kl_speed.png){.center fig-align="center"}

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## `Do I have to write everything?`

- TLDR: No
- Many cool projects already using Triton
- Better Integration with PyTorch and even Hugging Face 🤗
- Liger Kernel, Unsloth AI, etc.

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![](media/unsloth.png){.center fig-align="center"}

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![](media/liger.png){.center fig-align="center"}

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## `So how can I use this in my LLM? 🚀`

- Liger Kernel is a great example, providing examples of how to integrate with Hugging Face 🤗 Trainer

```diff
- from transformers import AutoModelForCausalLM
+ from liger_kernel.transformers import AutoLigerKernelForCausalLM

model_path = "meta-llama/Meta-Llama-3-8B-Instruct"

- model = AutoModelForCausalLM.from_pretrained(model_path)
+ model = AutoLigerKernelForCausalLM.from_pretrained(model_path)

# training/inference logic...
```
## `Key Optimization Techniques adapted by Liger Kernel`

- Kernel Fusion
- Domain-specific optimizations
- Memory Access Patterns
- Preemptive memory freeing
   

## `Aaand some more benchmarks 🚀`

- Saving memory is key to run bigger batch size on smaller GPUs

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![](media/PMA.png){fig-align="center"}

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![](media/PMR.png){fig-align="center"}

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## `Last benchmark I promise...`

- But is it faster? Yes, it is!

![](media/TPS.png){fig-align="center" height=50% width=50%}

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*Attention is all you need, so I thank you for yours!* 🤗

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![](media/qr.png){height=25% width=25% fig-align="center"}

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