/**
* 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.hadoop.mapred;
/**
*
* This class is a concrete PeriodicStatsAccumulator that deals with
* measurements where the raw data are a measurement of a
* time-varying quantity. The result in each bucket is the estimate
* of the progress-weighted mean value of that quantity over the
* progress range covered by the bucket.
*
* <p>An easy-to-understand example of this kind of quantity would be
* a temperature. It makes sense to consider the mean temperature
* over a progress range.
*
*/
class StatePeriodicStats extends PeriodicStatsAccumulator {
StatePeriodicStats(int count) {
super(count);
}
/**
*
* accumulates a new reading by keeping a running account of the
* area under the piecewise linear curve marked by pairs of
* {@code newProgress, newValue} .
*/
@Override
protected void extendInternal(double newProgress, int newValue) {
if (state == null) {
return;
}
// the effective height of this trapezoid if rectangularized
double mean = ((double)newValue + (double)state.oldValue)/2.0D;
// conceptually mean * (newProgress - state.oldProgress) / (1 / count)
state.currentAccumulation += mean * (newProgress - state.oldProgress) * count;
}
}