/**
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.mahout.utils;
/**
* Helps with making nice intervals at arbitrary scale.
*
* One use case is where we are producing progress or error messages every time an incoming
* record is received. It is generally bad form to produce a message for <i>every</i> input
* so it would be better to produce a message for each of the first 10 records, then every
* other record up to 20 and then every 5 records up to 50 and then every 10 records up to 100,
* more or less. The pattern can now repeat scaled up by 100. The total number of messages will scale
* with the log of the number of input lines which is much more survivable than direct output
* and because early records all get messages, we get indications early.
*/
public class Bump125 {
private static final int[] bumps = {1, 2, 5};
static int scale(double value, double base) {
double scale = value / base;
// scan for correct step
int i = 0;
while (i < bumps.length - 1 && bumps[i + 1] <= scale) {
i++;
}
return bumps[i];
}
static long base(double value) {
return Math.max(1, (long) Math.pow(10, (int) Math.floor(Math.log10(value))));
}
private long counter = 0;
public long increment() {
long delta;
if (counter >= 10) {
long base = base(counter / 4.0);
int scale = scale(counter / 4.0, base);
delta = base * scale;
} else {
delta = 1;
}
counter += delta;
return counter;
}
}