package water.util;
import java.util.Arrays;
import java.util.Random;
/**
* Shared static code to support modeling, prediction, and scoring.
*
* <p>Used by interpreted models as well as by generated model code.</p>
*
* <p><strong>WARNING:</strong> The class should have no other H2O dependencies
* since it is provided for generated code as h2o-model.jar which contains
* only a few files.</p>
*
*/
public class ModelUtils {
/**
* Sample out-of-bag rows with given rate with help of given sampler.
* It returns array of sampled rows. The first element of array contains a number
* of sampled rows. The returned array can be larger than number of returned sampled
* elements.
*
* @param nrows number of rows to sample from.
* @param rate sampling rate
* @param sampler random "dice"
* @return an array contains numbers of sampled rows. The first element holds a number of sampled rows. The array length
* can be greater than number of sampled rows.
*/
public static int[] sampleOOBRows(int nrows, float rate, Random sampler) {
return sampleOOBRows(nrows, rate, sampler, new int[2+Math.round((1f-rate)*nrows*1.2f+0.5f)]);
}
/**
* In-situ version of {@link #sampleOOBRows(int, float, Random)}.
*
* @param oob an initial array to hold sampled rows. Can be internally reallocated.
* @return an array containing sampled rows.
*
* @see #sampleOOBRows(int, float, Random)
*/
public static int[] sampleOOBRows(int nrows, float rate, Random sampler, int[] oob) {
int oobcnt = 0; // Number of oob rows
Arrays.fill(oob, 0);
for(int row = 0; row < nrows; row++) {
if (sampler.nextFloat() >= rate) { // it is out-of-bag row
oob[1+oobcnt++] = row;
if (1+oobcnt>=oob.length) oob = Arrays.copyOf(oob, Math.round(1.2f*nrows+0.5f)+2);
}
}
oob[0] = oobcnt;
return oob;
}
}