Most estimators in scikit-learn are designed to work with NumPy arrays or scipy sparse matricies. These data structures must fit in the RAM on a single machine.
Estimators implemented in Dask-ML work well with Dask Arrays and DataFrames. This can be much larger than a single machine's RAM. They can be distributed in memory on a cluster of machines.
from dask.distributed import Client # Scale up: connect to your own cluster with more resources # see http://dask.pydata.org/en/latest/setup.html client = Client(processes=False, threads_per_worker=4, n_workers=1, memory_limit='2GB') client
import dask_ml.datasets import dask_ml.cluster import matplotlib.pyplot as plt
In this example, we'll use
dask_ml.datasets.make_blobs to generate some random dask arrays.
# Scale up: increase n_samples or n_features X, y = dask_ml.datasets.make_blobs(n_samples=1000000, chunks=100000, random_state=0, centers=3) X = X.persist() X
We'll use the k-means implemented in Dask-ML to cluster the points. It uses the
k-means|| (read: "k-means parallel") initialization algorithm, which scales better than
k-means++. All of the computation, both during and after initialization, can be done in parallel.
km = dask_ml.cluster.KMeans(n_clusters=3, init_max_iter=2, oversampling_factor=10) km.fit(X)
We'll plot a sample of points, colored by the cluster each falls into.
fig, ax = plt.subplots() ax.scatter(X[::1000, 0], X[::1000, 1], marker='.', c=km.labels_[::1000], cmap='viridis', alpha=0.25);