doc/PR/ml__dataloader__resampling_8py.html

import ROOT

import torch


seed = 42

torch.manual_seed(seed)


# Create an imbalanced dataset with two classes, one of which is underrepresented.

# Here, we'll create two files, one with even numbers and one with odd numbers,

# and then merge them to form a dataset with underrepresented odd numbers.

def make_df(b1_expr, num_events):

    return ROOT.RDataFrame(num_events).Define("b1", b1_expr).Define("b2", "(int) b1%2")


df_major = make_df("(int) 2 * rdfentry_", 100000)

df_minor = make_df("(int) 2 * rdfentry_ + 1", 1000)


batch_size = 256

num_epochs = 20


loss_fn = torch.nn.BCEWithLogitsLoss()


# Function to train the model and print useful loss statistics

def train_model(model, optimizer, dataloader):

    train, val = dataloader.train_test_split(test_size=0.2)

    for _ in range(num_epochs):

        train_correct = 0

        train_total = 0

        train_losses = []

        model.train()

        for X, y in train.as_torch():

            optimizer.zero_grad()

            outputs = model(X)

            loss = loss_fn(outputs, y)

            loss.backward()

            optimizer.step()


            preds = (outputs > 0.5).float()

            train_correct += (preds == y).sum().item()

            train_total += y.size(0)

            train_losses.append(loss.item())

        print(

            f"Training   => Accuracy: {int(train_correct / train_total * 100000) / 100000}; Loss: {int(sum(train_losses) / len(train_losses) * 100000) / 100000}"

        )

    val_losses = []

    val_correct = 0

    val_total = 0

    for X, y in val.as_torch():

        with torch.no_grad():

            outputs = model(X)

            loss = loss_fn(outputs, y)


            preds = (outputs > 0.5).float()

            val_correct += (preds == y).sum().item()

            val_total += y.size(0)

            val_losses.append(loss.item())


    print(

        f"Validation => Accuracy: {int(val_correct / val_total * 100000) / 100000}; Loss: {int(sum(val_losses) / len(val_losses) * 100000) / 100000}\n"

    )


# Oversampling strategy: more batches of the underrepresented class

# Takes more time per epoch, but each epoch is more balanced & effective

dl_oversampled = ROOT.Experimental.ML.RDataLoader(

    [df_major, df_minor],

    batch_size=batch_size,

    target="b2",

    set_seed=seed,

    load_eager=True,  # Must be enabled for resampling

    sampling_type="oversampling",  # Can also be "undersampling"

    sampling_ratio=0.1,  # ~10% of the data will be from the underrepresented class, instead of ~1%

)


oversampling_model = torch.nn.Linear(1, 1)

oversampling_optimizer = torch.optim.Adam(oversampling_model.parameters())


print("Training with oversampling:")

train_model(oversampling_model, oversampling_optimizer, dl_oversampled)

Define
RInterface< Proxied > Define(std::string_view name, F expression, const ColumnNames_t &columns={})
Define a new column.
Definition RInterface.hxx:1475

ROOT::RDataFrame
ROOT's RDataFrame offers a modern, high-level interface for analysis of data stored in TTree ,...
Definition RDataFrame.hxx:50

sum
static uint64_t sum(uint64_t i)
Definition Factory.cxx:2338