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GPULlama3.java

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GPU-accelerated Llama3.java inference in pure Java using TornadoVM.

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# GPULlama3.java — LLM inference & serving for the JVM, on any GPU

[![build JDK21](https://github.com/beehive-lab/GPULlama3.java/actions/workflows/build-and-run.yml/badge.svg)](https://github.com/beehive-lab/GPULlama3.java/actions/workflows/build-and-run.yml)
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![Java 21](https://img.shields.io/badge/java-21-blue?logo=openjdk)
![Java 25](https://img.shields.io/badge/java-25-yellow?logo=openjdk)
[![LangChain4j](https://img.shields.io/badge/LangChain4j-1.7.1+-purple?&logo=link&logoColor=white)](https://docs.langchain4j.dev/)
![NVIDIA](https://img.shields.io/badge/CUDA%20%7C%20PTX-supported-76B900?logo=nvidia)
![OpenCL](https://img.shields.io/badge/OpenCL-supported-blue?logo=khronos)
![Apple](https://img.shields.io/badge/Metal-Apple%20Silicon-black?logo=apple)
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[![DeepWiki](https://deepwiki.com/badge.svg)](https://deepwiki.com/beehive-lab/GPULlama3.java)
[![License: MIT](https://img.shields.io/badge/License-MIT-green.svg)](https://raw.githubusercontent.com/beehive-lab/GPULlama3.java/main/LICENSE)

-----------

### Think vLLM — but pure Java, and it runs on **any** GPU.

**GPULlama3.java** is a JVM-native LLM inference and serving engine. You write and ship plain Java; [**TornadoVM**](https://github.com/beehive-lab/TornadoVM) JIT-compiles the hot transformer kernels to **CUDA, PTX, OpenCL, or Apple Metal** at runtime — no JNI glue, no second toolchain, no native rebuild per GPU.

One `.jar` runs the same model on **NVIDIA, Intel, AMD, and Apple Silicon**, from a laptop to an RTX 5090.

Serve it behind an **OpenAI-compatible API**, embed it in **LangChain4j** or **Quarkus**, or run it from the CLI in one line.

</td>
</tr>
</table>

Builds on [Llama3.java](https://github.com/mukel/llama3.java) by [Alfonso² Peterssen](https://github.com/mukel). Earlier Llama2 work: [llama2.tornadovm](https://github.com/mikepapadim/llama2.tornadovm.java).

-----------

## Why GPULlama3.java

- 🟦 **Pure Java, all the way down.** Transformer kernels are written in Java and accelerated by TornadoVM — no CUDA C, no hand-written JNI. Debug and build with the toolchain you already have.
- 🌍 **Write once, run on any GPU.** NVIDIA (CUDA / PTX), Intel & AMD (OpenCL), Apple Silicon (Metal). Backend is auto-detected from your TornadoVM SDK — switch with a flag, not a rebuild.
- 🔌 **Drop-in for the Java AI stack.** Official [LangChain4j](https://docs.langchain4j.dev/integrations/language-models/gpullama3-java) provider (since v1.7.1) and [Quarkus](https://docs.quarkiverse.io/quarkus-langchain4j/dev/gpullama3-chat-model.html) inference engine.
- ⚡ **Built to serve.** OpenAI-compatible HTTP server, llama-bench-style benchmarking, and tensor-core (MMA) batch prefill (see [Serving](#-serving-openai-compatible-preview)).
- 📦 **Many models, one runtime.** Llama 3, Mistral, Qwen 2.5 / Qwen 3, Phi-3, IBM Granite 3.3 / 4.0, DeepSeek-R1-Distill — all in GGUF.

-----------

## ⏱️ Quickstart (60 seconds)

```bash
# 1. Install a TornadoVM SDK (bundles the GPU runtime)
curl -s "https://get.sdkman.io" | bash && source "$HOME/.sdkman/bin/sdkman-init.sh"
sdk install tornadovm
tornado --devices        # confirm your GPU is listed

# 2. Run a model on the GPU — no build required, via JBang
jbang gpullama3@beehive-lab -m beehive-llama-3.2-1b-instruct-fp16.gguf -p "Explain GPU acceleration in one sentence."
```

Grab a ready-to-run model from the [Hugging Face collections](#-model-collections) below.

-----------

## 🧩 Serving: OpenAI-compatible (preview)

GPULlama3.java is growing into a **serving engine** — the vLLM-style path for the JVM:

- 🌐 **OpenAI-compatible server** — `llama-tornado --server` exposes `/v1/chat/completions` and `/v1/completions` with streaming and zero external dependencies. Point any OpenAI client at `localhost`. See [OpenAI-compatible server](#-openai-compatible-server---server) below.
- 🎯 **Tensor-core (MMA) batch prefill** on the CUDA backend, FP16 & Q8_0 — `--with-prefill-decode --batch-prefill-size N`.
- 📈 **llama-bench-style benchmarking** — `llama-tornado --bench` reports a pp/tg matrix with avg±stddev in md/csv/json/jsonl/sql. See [Benchmarking](#-benchmarking---bench-llama-bench-style) below.
- 🧮 **On-device greedy sampling** *(landing next)* — argmax on the GPU keeps logits device-side, cutting device→host traffic by ~500× per token. ([PR #134](https://github.com/beehive-lab/GPULlama3.java/pull/134))
- 📚 **Static batched decode** *(landing next)* — B independent sequences per step for up to **41× aggregate throughput** (Llama & Qwen3). ([PR #129](https://github.com/beehive-lab/GPULlama3.java/pull/129))

-----------

## <img src="https://github.com/user-attachments/assets/51b76554-0b01-4e18-a567-600901ab8c5f" alt="LangChain4j" height="30" style="vertical-align: middle; margin-right: 8px;"> LangChain4j & Quarkus

Since **LangChain4j v1.7.1**, `GPULlama3.java` is an officially supported **model provider** — no glue code, GPU-accelerated out of the box.

```java
GPULlama3ChatModel model = GPULlama3ChatModel.builder()
        .modelPath(modelPath)
        .temperature(0.9)      // more creative
        .topP(0.9)             // more variety
        .maxTokens(2048)
        .onGPU(Boolean.TRUE)   // false → lightweight CPU llama3.java
        .build();
```

📖 [LangChain4j docs](https://docs.langchain4j.dev/) · 🚀 [Agentic workflow demo](https://github.com/mikepapadim/devoxx25-demo-gpullama3-langchain4j/tree/main)

### 📦 Maven

**JDK 21** (`jdk21` profile, auto-activates for JDK `[21,25)`):
```xml
<dependency>
    <groupId>io.github.beehive-lab</groupId>
    <artifactId>gpu-llama3</artifactId>
    <version>1.0.0-jdk21</version>
</dependency>
```

**JDK 25** (`jdk25` profile, auto-activates for JDK `[25.0.2,)`):
```xml
<dependency>
    <groupId>io.github.beehive-lab</groupId>
    <artifactId>gpu-llama3</artifactId>
    <version>1.0.0-jdk25</version>
</dependency>
```

### 📦 Gradle

**JDK 21**:
```groovy
implementation 'io.github.beehive-lab:gpu-llama3:1.0.0-jdk21'
```

**JDK 25**:
```groovy
implementation 'io.github.beehive-lab:gpu-llama3:1.0.0-jdk25'
```

-----------

#### **[Interactive mode]** — RTX 5090, with `nvtop` tracking GPU utilization and memory

![Demo](https://raw.githubusercontent.com/beehive-lab/GPULlama3.java/main/docs/inter-output.gif)

-----------

## 🛠️ Install & build

### Prerequisites

- **Java 21** — required for the Vector API & TornadoVM (Java 25 supported via the `-jdk25` artifact / `llamaTornado` script).
- **[TornadoVM](https://github.com/beehive-lab/TornadoVM)** with an OpenCL, PTX, CUDA, or Metal backend. `llama-tornado`/`llamaTornado` auto-detect whichever backend your installed SDK was built with.
- **GCC/G++ 13+** — to build TornadoVM's native components.

### Get TornadoVM (SDKMAN!, recommended)

TornadoVM is distributed via the [official website](https://www.tornadovm.org/downloads) and [SDKMAN!](https://sdkman.io/sdks/tornadovm/). Pick a package matching your OS, architecture, and backend (opencl, ptx).

```bash
sdk install tornadovm
tornado --devices        # verify
```

### Clone this repo

```bash
git clone https://github.com/beehive-lab/GPULlama3.java.git
```

-----------

## ▶️ Running the CLI

Use the `llama-tornado` script with `--gpu`. The backend (OpenCL, PTX, CUDA, or Metal) is auto-detected from
your installed TornadoVM SDK (`TORNADOVM_HOME/etc/tornado.backend`) — no need to select it manually. If your
SDK was built with more than one backend, force one with `--opencl`, `--ptx`, `--cuda` (NVIDIA), or `--metal`
(Apple Silicon); forcing a backend that isn't part of the installed SDK errors out.

```bash
# Basic GPU inference — backend auto-detected
./llama-tornado --gpu --verbose-init \
  --model beehive-llama-3.2-1b-instruct-fp16.gguf \
  --prompt "Explain the benefits of GPU acceleration."

# Force a specific backend (only needed for multi-backend SDKs)
./llama-tornado --gpu --cuda \
  --model beehive-llama-3.2-1b-instruct-fp16.gguf \
  --prompt "Explain the benefits of GPU acceleration."
```

Swap in any tested model — e.g. `beehive-llama-3.2-3b-instruct-fp16.gguf` or `...-8b-...`.

### `llamaTornado` — zero-dependency Java 25 script

Same backend auto-detection as `llama-tornado`. A single-file Java 25 launcher that replaces the Python
script (needs `java 25+` on your PATH):

```bash
./llamaTornado --gpu --verbose-init --metal \
  --model Mistral-7B-Instruct-v0.3.Q8_0.gguf --prompt "what is java"
```

### 🚀 JBang — run without building

Script-like startup à la [Jlama](https://github.com/tjake/Jlama), powered by [JBang](https://www.jbang.dev/):

```bash
curl -Ls https://sh.jbang.dev | bash -s - app setup

# From the catalog
jbang gpullama3@beehive-lab -m model.gguf -p "Tell me a joke"
jbang app install gpullama3@beehive-lab && gpullama3 -m model.gguf -p "Hello!"

# Or the local script, interactive
jbang LlamaTornadoCli.java -m beehive-llama-3.2-1b-instruct-fp16.gguf --interactive
```

### 🐳 Docker

Fully containerized GPU inference via pre-built images ([docker-gpullama3.java](https://github.com/beehive-lab/docker-gpullama3.java)):

| Backend | Image |
|---------|-------|
| **OpenCL** | [`beehivelab/gpullama3.java-nvidia-openjdk-opencl`](https://hub.docker.com/r/beehivelab/gpullama3.java-nvidia-openjdk-opencl) |
| **PTX (CUDA)** | [`beehivelab/gpullama3.java-nvidia-openjdk-ptx`](https://hub.docker.com/r/beehivelab/gpullama3.java-nvidia-openjdk-ptx) |

```bash
docker run --rm -it --gpus all -v "$PWD":/data \
  beehivelab/gpullama3.java-nvidia-openjdk-opencl \
  /gpullama3/GPULlama3.java/llama-tornado \
  --gpu --verbose-init \
  --model /data/Llama-3.2-1B-Instruct.FP16.gguf --prompt "Tell me a joke"
```

-----------

## 🤗 Model collections

GGUF models, ready to download:

| Family | Collection |
|--------|-----------|
| Llama 3.2 | [llama3-gpullama3java](https://huggingface.co/collections/beehive-lab/llama3-gpullama3java) |
| IBM Granite 4.0 | [granite-40-language-models](https://huggingface.co/collections/beehive-lab/granite-40-language-models-gpullama3java) |
| IBM Granite 3.3 | [granite-33-language-models](https://huggingface.co/collections/beehive-lab/granite-33-language-models-gpullama3java) |
| Qwen 2.5 | [qwen-25-gpullama3java](https://huggingface.co/collections/beehive-lab/qwen-25-gpullama3java) |
| Qwen 3 | [qwen-3-gpullama3java](https://huggingface.co/collections/beehive-lab/qwen-3-gpullama3java) |
| Phi-3 | [phi-3-gpullama3java](https://huggingface.co/collections/beehive-lab/phi-3-gpullama3java) |
| Mistral | [mistral-gpullama3java](https://huggingface.co/collections/beehive-lab/mistral-gpullama3java) |
| DeepSeek-R1-Distill-Qwen | [deepseek-r1-distill-qwen](https://huggingface.co/collections/beehive-lab/deepseek-r1-distill-qwen-gpullama3java) |

Formats: GGUF · FP16 (full), Q8_0 & Q4_0 (partial).

-----------

## 💾 GPU memory

Default device allocation is **14GB**. Larger models need more — raise it with `--gpu-memory`:

| Model size | Recommended | Flag |
|------------|-------------|------|
| 1B  | 14GB (default) | — |
| 3–7B | 15GB+ | `--gpu-memory 15GB` |
| 8B+ | 20GB+ | `--gpu-memory 20GB` |

```bash
./llama-tornado --gpu --model beehive-llama-3.2-3b-instruct-fp16.gguf \
  --prompt "Tell me a joke" --gpu-memory 15GB
```

Still out of memory? Use Q4_0 instead of Q8_0, or close other GPU apps. The error to look for:

```
TornadoOutOfMemoryException: Unable to allocate ... bytes of memory.
To increase the maximum device memory, use -Dtornado.device.memory=<X>GB
```

-----------

## 🔧 Embed in your own tools

`--show-command` prints the exact Java + JVM invocation used under the hood, so you can replicate it in IntelliJ, Maven, Gradle, or any launcher:

```bash
llama-tornado --gpu --model beehive-llama-3.2-1b-instruct-fp16.gguf \
  --prompt "tell me a joke" --show-command
```

<details>
<summary>📋 Full command-line options (<code>llama-tornado --help</code>)</summary>

```
usage: llama-tornado [-h] --model MODEL_PATH [--prompt PROMPT] [-sp SYSTEM_PROMPT]
                     [--temperature TEMPERATURE] [--top-p TOP_P] [--seed SEED] [-n MAX_TOKENS]
                     [--stream STREAM] [--echo ECHO] [-i] [--instruct]
                     [--server] [--port PORT] [--bench] [--bench-args BENCH_ARGS]
                     [--gpu] [--opencl] [--ptx] [--cuda] [--metal]
                     [--gpu-memory GPU_MEMORY] [--heap-min HEAP_MIN] [--heap-max HEAP_MAX]
                     [--debug] [--profiler] [--profiler-dump-dir DIR]
                     [--print-bytecodes] [--print-threads] [--print-kernel] [--full-dump]
                     [--show-command] [--execute-after-show]
                     [--with-prefill-decode] [--batch-prefill-size N] [--cuda-graphs]
                     [--opencl-flags FLAGS] [--max-wait-events N] [--verbose]

LLaMA Configuration:  --prompt, -sp/--system-prompt, --temperature (0.0–2.0, default 0.1),
                      --top-p (default 0.95), --seed, -n/--max-tokens (default 512),
                      --stream (default True), --echo (default False), --suffix (FIM/Codestral)
Mode Selection:       -i/--interactive, --instruct (default)
OpenAI server:        --server (run the HTTP server instead of inference), --port (default 8080)
Benchmark:            --bench (llama-bench-style matrix), --bench-args="..." (see Benchmarking below)
Hardware:             --gpu, --opencl/--ptx/--cuda/--metal (auto-detected; force one of the installed
                      backends), --gpu-memory (default 14GB), --heap-min/--heap-max (default 20g)
Debug & Profiling:    --debug, --profiler, --profiler-dump-dir,
                      --print-bytecodes, --print-threads, --print-kernel, --full-dump, --verbose-init
Command Display:      --show-command, --execute-after-show
Prefill-Decode:       --with-prefill-decode, --batch-prefill-size N (tensor-core MMA batch prefill,
                      FP16 & Q8_0)
Advanced:             --cuda-graphs (PTX backend only), --opencl-flags (default: -cl-denorms-are-zero
                      -cl-no-signed-zeros -cl-finite-math-only), --max-wait-events (default 32000), --verbose/-v
```

</details>

```bash
# Peek at what TornadoVM is doing
./llama-tornado --gpu --model model.gguf --prompt "..." --print-kernel      # generated GPU kernel
./llama-tornado --gpu --model model.gguf --prompt "..." --print-bytecodes   # TornadoVM bytecodes
./llama-tornado --gpu --model model.gguf --prompt "..." --debug --full-dump # everything
```

-----------

## 🗺️ Features & roadmap

- ✅ **GGUF models** — full FP16, partial Q8_0 / Q4_0.
- ✅ **Chat, instruction, and interactive** modes (`--interactive`, `--instruct`).
- ✅ **Automatic backend detection** — `llama-tornado`/`llamaTornado` detect and use whichever backend (OpenCL, PTX, CUDA, or Metal) your installed TornadoVM SDK was built with; override with `--opencl`/`--ptx`/`--cuda`/`--metal`.
- ✅ **Cross-platform**: NVIDIA (OpenCL · PTX · CUDA), Intel (OpenCL), Apple (OpenCL · Metal).
- ✅ **Serving** — OpenAI-compatible API, llama-bench-style benchmarking, tensor-core (MMA) batch prefill.
- 🧩 **Coming next** — static batched decode, on-device sampling (preview; see [Serving](#-serving-openai-compatible-preview)).

📄 [Transformer optimizations in TornadoVM](docs/TORNADOVM_TRANSFORMER_OPTIMIZATIONS.md) · 🧭 [Project roadmap](docs/GPULlama3_ROADMAP.md)

-----------

## 🙏 Acknowledgments

Partially funded by EU Horizon Europe & UKRI grants (most recent first):
[AERO 101092850](https://aero-project.eu/) · [P2CODE 101093069](https://p2code-project.eu/) · [ENCRYPT 101070670](https://encrypt-project.eu) · [TANGO 101070052](https://tango-project.eu).

## License

[MIT](LICENSE)

GPULlama3.java

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