concrete/docs/user/howto/compiling_torch_model.md

Compiling a Torch Model

Concrete Framework allows to compile a torch model to its FHE counterpart.

A simple command can compile a torch model to its FHE counterpart. This process executes most of the concepts described in the documentation on how to use quantization and triggers the compilation to be able to run the model over homomorphically encrypted data.

from torch import nn
import torch
torch.manual_seed(0)
class LogisticRegression(nn.Module):
    """LogisticRegression with Torch"""

    def __init__(self):
        super().__init__()
        self.fc1 = nn.Linear(in_features=14, out_features=1)
        self.sigmoid1 = nn.Sigmoid()


    def forward(self, x):
        """Forward pass."""
        out = self.fc1(x)
        out = self.sigmoid1(out)
        return out

torch_model = LogisticRegression()

Note that the architecture of the neural network passed to be compiled must respect some hard constraints given by FHE. Please read the our [detailed documentation](../howto/reduce_needed_precision.md) on these limitations.

Once your model is trained you can simply call the compile_torch_model function to execute the compilation.

from concrete.torch.compile import compile_torch_model
import numpy
torch_input = torch.randn(100, 14)
quantized_numpy_module = compile_torch_model(
    torch_model, # our model
    torch_input, # a representative inputset to be used for both quantization and compilation
    n_bits = 2,
)

You can then call quantized_numpy_module.forward_fhe.run() to have the FHE inference.

Now your model is ready to infer in FHE settings !

enc_x = numpy.array([numpy.random.randn(14)]).astype(numpy.uint8) # An example that is going to be encrypted, and used for homomorphic inference.
fhe_prediction = quantized_numpy_module.forward_fhe.run(enc_x)

fhe_prediction contains the clear quantized output. The user can now dequantize the output to get the actual floating point prediction as follows:

clear_output = quantized_numpy_module.dequantize_output(
    numpy.array(fhe_prediction, dtype=numpy.float32)
)

If you want to see more compilation examples, you can check out the IrisFHE notebook