/*
* Licensed 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 com.facebook.presto.operator.aggregation;
import com.facebook.presto.block.Block;
import com.facebook.presto.block.BlockBuilder;
import static com.facebook.presto.operator.aggregation.LongApproximateAverageAggregation.LONG_APPROX_AVERAGE;
import static com.facebook.presto.tuple.TupleInfo.SINGLE_LONG;
public class TestLongApproximateAverageAggregation
extends AbstractTestAggregationFunction
{
@Override
public Block getSequenceBlock(int start, int length)
{
BlockBuilder blockBuilder = new BlockBuilder(SINGLE_LONG);
for (int i = start; i < start + length; i++) {
blockBuilder.append(i);
}
return blockBuilder.build();
}
@Override
public AggregationFunction getFunction()
{
return LONG_APPROX_AVERAGE;
}
@Override
public String getExpectedValue(int start, int length)
{
if (length == 0) {
return null;
}
double sum = 0;
for (int i = start; i < start + length; i++) {
sum += i;
}
double mean = sum / length;
double m2 = 0.0;
for (int i = start; i < start + length; i++) {
m2 += (i - mean) * (i - mean);
}
double variance = m2 / length;
StringBuilder sb = new StringBuilder();
sb.append(mean);
sb.append(" +/- ");
sb.append((2.575 * Math.sqrt(variance / length)));
return sb.toString();
}
}