# gpt-2

This is a C++ example running GPT-2 inference using the [ggml](https://github.com/ggerganov/ggml) library.
The enitre code of the example is in [main.cpp](main.cpp).

The program runs on the CPU - no video card is required.

The example supports the following models:

| Model | Description  | Disk Size |
| ---   | ---          | ---       |
| 117M  | Small model  | 240 MB    |
| 345M  | Medium model | 680 MB    |
| 774M  | Large model  | 1.5 GB    |
| 1558M | XL model     | 3.0 GB    |

Sample performance on MacBook M1 Pro:

| Model | Size  | Time / Token |
| ---   | ---   | ---    |
| GPT-2 |  117M |   5 ms |
| GPT-2 |  345M |  12 ms |
| GPT-2 |  774M |  23 ms |
| GPT-2 | 1558M |  42 ms |

Sample output:

```
$ ./bin/gpt-2 -h
usage: ./bin/gpt-2 [options]

options:
  -h, --help            show this help message and exit
  -s SEED, --seed SEED  RNG seed (default: -1)
  -t N, --threads N     number of threads to use during computation (default: 8)
  -p PROMPT, --prompt PROMPT
                        prompt to start generation with (default: random)
  -n N, --n_predict N   number of tokens to predict (default: 200)
  --top_k N             top-k sampling (default: 40)
  --top_p N             top-p sampling (default: 0.9)
  --temp N              temperature (default: 1.0)
  -b N, --batch_size N  batch size for prompt processing (default: 8)
  -m FNAME, --model FNAME
                        model path (default: models/gpt-2-117M/ggml-model.bin)

$ ./bin/gpt-2
gpt2_model_load: loading model from 'models/gpt-2-117M/ggml-model.bin'
gpt2_model_load: n_vocab = 50257
gpt2_model_load: n_ctx   = 1024
gpt2_model_load: n_embd  = 768
gpt2_model_load: n_head  = 12
gpt2_model_load: n_layer = 12
gpt2_model_load: f16     = 1
gpt2_model_load: ggml ctx size = 311.12 MB
gpt2_model_load: memory size =    72.00 MB, n_mem = 12288
gpt2_model_load: model size  =   239.08 MB
main: number of tokens in prompt = 1

So this is going to be the end of the line for us.

If the Dolphins continue to do their business, it's possible that the team could make a bid to bring in new defensive coordinator Scott Linehan.

Linehan's job is a little daunting, but he's a great coach and an excellent coach. I don't believe we're going to make the playoffs.

We're going to have to work hard to keep our heads down and get ready to go.<|endoftext|>

main: mem per token =  2048612 bytes
main:     load time =   106.32 ms
main:   sample time =     7.10 ms
main:  predict time =   506.40 ms / 5.06 ms per token
main:    total time =   629.84 ms
```

## Downloading and converting the original models

You can download the original model files using the [download-model.sh](download-model.sh) Bash script.
The model is in Tensorflow format, so before using it with ggml, we need to convert it to appropriate format.
This is done via the [convert-ckpt-to-ggml.py](convert-ckpt-to-ggml.py) python script.

Here is the entire process for the GPT-2 117M model:

```
cd ggml/build
../examples/gpt-2/download-model.sh 117M

Downloading model 117M ...
models/gpt-2-117M/checkpoint                      100%[=============================>]      77  --.-KB/s    in 0s
models/gpt-2-117M/encoder.json                    100%[=============================>]   1018K  1.20MB/s    in 0.8s
models/gpt-2-117M/hparams.json                    100%[=============================>]      90  --.-KB/s    in 0s
models/gpt-2-117M/model.ckpt.data-00000-of-00001  100%[=============================>] 474.70M  1.21MB/s    in 8m 39s
models/gpt-2-117M/model.ckpt.index                100%[=============================>]   5.09K  --.-KB/s    in 0s
models/gpt-2-117M/model.ckpt.meta                 100%[=============================>] 460.11K   806KB/s    in 0.6s
models/gpt-2-117M/vocab.bpe                       100%[=============================>] 445.62K   799KB/s    in 0.6s
Done! Model '117M' saved in 'models/gpt-2-117M/'

Run the convert-ckpt-to-ggml.py script to convert the model to ggml format.

  python /Users/john/ggml/examples/gpt-2/convert-ckpt-to-ggml.py models/gpt-2-117M/

```

This conversion requires that you have python and Tensorflow installed on your computer.
Still, if you want to avoid this, you can download the already converted ggml models as
described below.

## Downloading the ggml model directly

For convenience, I will be hosting the converted ggml model files in order to make it easier to run the examples.
This way, you can directly download a single binary file and start using it. No python or Tensorflow is required.

Here is how to get the 117M ggml model:

```
cd ggml/build
../examples/gpt-2/download-ggml-model.sh 117M

Downloading ggml model 117M ...
models/gpt-2-117M/ggml-model.bin         100%[===============================>] 239.58M  8.52MB/s    in 28s
Done! Model '117M' saved in 'models/gpt-2-117M/ggml-model.bin'
You can now use it like this:

  $ ./bin/gpt-2 -m models/gpt-2-117M/ggml-model.bin -p "This is an example"

```

At some point, I might stop hosting these models. So in that case, simply revert to the manual process above.