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/*
* Copyright 2023 The original authors
*
* 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 dev.morling.onebrc;
import java.io.FileInputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.util.*;
import java.util.concurrent.atomic.DoubleAccumulator;
import java.util.concurrent.atomic.LongAdder;
import java.util.stream.Collectors;
import java.util.stream.StreamSupport;
public class CalculateAverage_truelive {
private static final String FILE = "./measurements.txt";
private static final long CHUNK_SIZE = 1024 * 1024 * 10L;
private static int branchlessParseInt(final byte[] input, final int length) {
// 0 if positive, 1 if negative
final int negative = ~(input[0] >> 4) & 1;
// 0 if nr length is 3, 1 if length is 4
final int has4 = ((length - negative) >> 2) & 1;
final int digit1 = input[negative] - '0';
final int digit2 = input[negative + has4] - '0';
final int digit3 = input[2 + negative + has4] - '0';
return (-negative ^ (has4 * (digit1 * 100) + digit2 * 10 + digit3) - negative);
}
// branchless max (unprecise for large numbers, but good enough)
static int max(final int a, final int b) {
final int diff = a - b;
final int dsgn = diff >> 31;
return a - (diff & dsgn);
}
// branchless min (unprecise for large numbers, but good enough)
static int min(final int a, final int b) {
final int diff = a - b;
final int dsgn = diff >> 31;
return b + (diff & dsgn);
}
private record Measurement(DoubleAccumulator min, DoubleAccumulator max, DoubleAccumulator sum, LongAdder count) {
public static Measurement of(final Double initialMeasurement) {
final Measurement measurement = new Measurement(
new DoubleAccumulator(Math::min, initialMeasurement),
new DoubleAccumulator(Math::max, initialMeasurement),
new DoubleAccumulator(Double::sum, initialMeasurement),
new LongAdder()
);
measurement.count.increment();
return measurement;
}
public Measurement add(final double measurment) {
min.accumulate(measurment);
max.accumulate(measurment);
sum.accumulate(measurment);
count.increment();
return this;
}
public String toString() {
return round(min.doubleValue()) +
"/" +
round(sum.doubleValue() / count.sum()) +
"/" +
round(max.doubleValue());
}
private double round(final double value) {
return Math.round(value * 10.0) / 10.0;
}
public static Measurement combineWith(final Measurement m1, final Measurement m2) {
m1.min.accumulate(m2.min.doubleValue());
m1.max.accumulate(m2.max.doubleValue());
m1.sum.accumulate(m2.sum.doubleValue());
m1.count.add(m2.count.sum());
return new Measurement(
m1.min,
m1.max,
m1.sum,
m1.count
);
}
}
private static Map<String, Measurement> combineMaps(
final Map<String, Measurement> map1,
final Map<String, Measurement> map2
) {
for (final var entry : map2.entrySet()) {
map1.merge(entry.getKey(), entry.getValue(), Measurement::combineWith);
}
return map1;
}
public static void main(final String[] args) throws IOException {
//long before = System.currentTimeMillis();
/**
* Shoutout to bjhara
*/
final Iterator<ByteBuffer> iterator = new Iterator<>() {
final FileChannel in = new FileInputStream(FILE).getChannel();
final long total = in.size();
long start;
@Override
public boolean hasNext() {
return start < total;
}
@Override
public ByteBuffer next() {
try {
final MappedByteBuffer mbb = in.map(
FileChannel.MapMode.READ_ONLY,
start,
Math.min(CHUNK_SIZE, total - start)
);
int realEnd = mbb.limit() - 1;
while (mbb.get(realEnd) != '\n') {
realEnd--;
}
realEnd++;
mbb.limit(realEnd);
start += realEnd;
return mbb;
} catch (final IOException e) {
throw new RuntimeException(e);
}
}
};
final Map<String, Measurement> reduce = StreamSupport.stream(Spliterators.spliteratorUnknownSize(
iterator, Spliterator.IMMUTABLE), true)
.parallel()
.map(CalculateAverage_truelive::parseBuffer)
.reduce(CalculateAverage_truelive::combineMaps).get();
System.out.print("{");
System.out.print(
reduce
.entrySet()
.stream()
.sorted(Map.Entry.comparingByKey())
.map(Object::toString)
.collect(Collectors.joining(", ")));
System.out.println("}");
//System.out.println("Took: " + (System.currentTimeMillis() - before));
}
private static Map<String, Measurement> parseBuffer(final ByteBuffer bug) {
final Map<String, Measurement> resultMap = new HashMap<>();
bug.mark();
String name = null;
final byte[] arr = new byte[128];
while (bug.hasRemaining()) {
final char c = (char) bug.get();
if (c == ';') {
final int pos = bug.position();
bug.reset();
final int len = pos - bug.position() - 1;
bug.get(bug.position(), arr, 0, len);
name = new String(arr, 0, len);
bug.position(pos);
bug.mark();
} else if (c == '\n') {
final int pos = bug.position();
bug.reset();
final int len = pos - bug.position();
bug.get(bug.position(), arr, 0, len);
final double temp = Double.parseDouble(new String(arr, 0, len));
resultMap.compute(name, (k, v) -> (v == null) ? Measurement.of(temp) : v.add(temp));
bug.position(pos);
bug.mark();
}
}
return resultMap;
}
}
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