The product nkd is given in millions, and z*, have been rounded to integers. Computing times t, to are in seconds for the small instances, and in hours for the large ones.

Results of O-K-means for still larger instances.

Information to seize the relationship between computational effort and solution quality.

Correlation coefficients of synthetic and real instances.

Some results of the K-means algorithm with a randomly generated instance where n = 2 ⋅ 106, k = 200, and d = 2.

The n values are given in millions.

Time and quality reduction arising from combining F and P algorithms with O-K-means.

Results of O-K-means for a 2-dimensional, non uniform synthetic instance.

Computer times t and to are given in hours, the product nkd in millions.

Results of OK, FOK and POK when using as initial centroids those generated by K++.