ray-skorch 0.0.3
Skorch on Ray Train

# ray-skorch

*Distributed skorch on Ray Train*

`pip install ray-skorch`

[skorch](https://github.com/skorch-dev/skorch)-based wrapper for [Ray Train](https://docs.ray.io/en/latest/train/train.html). Experimental!

> :warning: `RayTrainNeuralNet` and the rest of this package are experimental and not production ready. In particular, validation and error handling may be spotty. If you encounter any problems or have any suggestions please open an issue on GitHub.

We are looking for feedback! Please let us know about your experience using ray-skorch and about any suggestions and problems you may have by opening an issue. We are also interested in feedback on the concept of distributed training with scikit-learn(like) interfaces itself.

## Development

1. Run `pip install -e .` to install necessary packages
2. Upon push, run `./format.sh` to make sure lint changes are applied appropriately.
3. The current working examples can be found in `examples`.

## Known issues & missing features

* Only numpy arrays, pandas dataframes and Ray Data Datasets are supported as inputs.
* Compatibility with scikit-learn hyperparameter tuners is not tested.

## Basic example

The only breaking API difference compared to `skorch` is the addition of a new `num_workers` argument, contolling how many Ray workers to use for training. Please refer to docstrings for more information on other changes.

### With numpy/pandas

```python
import numpy as np
from sklearn.datasets import make_classification
from torch import nn

from ray_skorch import RayTrainNeuralNet

X, y = make_classification(1000, 20, n_informative=10, random_state=0)
X = X.astype(np.float32)
y = y.astype(np.int64)


class MyModule(nn.Module):
    def __init__(self, num_units=10, nonlin=nn.ReLU()):
        super(MyModule, self).__init__()

        self.dense0 = nn.Linear(20, num_units)
        self.nonlin = nonlin
        self.dropout = nn.Dropout(0.5)
        self.dense1 = nn.Linear(num_units, num_units)
        self.output = nn.Linear(num_units, 2)

    def forward(self, X, **kwargs):
        X = self.nonlin(self.dense0(X))
        X = self.dropout(X)
        X = self.nonlin(self.dense1(X))
        X = self.output(X)
        return X

net = RayTrainNeuralNet(
    MyModule,
    num_workers=2,  # the only new mandatory argument
    criterion=nn.CrossEntropyLoss,
    max_epochs=10,
    lr=0.1,
    # required for classification loss funcs
    iterator_train__unsqueeze_label_tensor=False,
    iterator_valid__unsqueeze_label_tensor=False,
)

net.fit(X, y)

# predict_proba returns a ray.data.Dataset
y_proba = net.predict_proba(X).to_pandas()
print(y_proba)
```

### With Ray Data

```python
import numpy as np
import pandas as pd
from sklearn.datasets import make_classification
from torch import nn
from ray.data import from_pandas

from ray_skorch import RayTrainNeuralNet

X, y = make_classification(1000, 20, n_informative=10, random_state=0)
X = pd.DataFrame(X.astype(np.float32))
y = pd.Series(y.astype(np.int64))
X.columns = [str(colname) for colname in X.columns]

X_pred = X.copy()
X["target"] = y

X = from_pandas(X)
# ensure no target column is in data for prediction
X_pred = from_pandas(X_pred)

class MyModule(nn.Module):
    def __init__(self, num_units=10, nonlin=nn.ReLU()):
        super(MyModule, self).__init__()

        self.dense0 = nn.Linear(20, num_units)
        self.nonlin = nonlin
        self.dropout = nn.Dropout(0.5)
        self.dense1 = nn.Linear(num_units, num_units)
        self.output = nn.Linear(num_units, 2)

    def forward(self, X, **kwargs):
        X = self.nonlin(self.dense0(X))
        X = self.dropout(X)
        X = self.nonlin(self.dense1(X))
        X = self.output(X)
        return X

net = RayTrainNeuralNet(
    MyModule,
    num_workers=2,  # the only new mandatory argument
    criterion=nn.CrossEntropyLoss,
    max_epochs=10,
    lr=0.1,
    # required for classification loss funcs
    iterator_train__unsqueeze_label_tensor=False,
    iterator_valid__unsqueeze_label_tensor=False,
)

net.fit(X, "target")

# predict_proba returns a ray.data.Dataset
y_proba = net.predict_proba(X_pred).to_pandas()
print(y_proba)
```