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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 static java.lang.foreign.ValueLayout.JAVA_BYTE;
import static java.nio.file.StandardOpenOption.READ;
import java.io.IOException;
import java.lang.foreign.Arena;
import java.lang.foreign.MemorySegment;
import java.nio.channels.FileChannel;
import java.nio.file.Path;
import java.util.HashMap;
import java.util.Map;
import java.util.stream.Collectors;
import java.util.stream.IntStream;
public class CalculateAverage_0xshivamagarwal {
private static final Path FILE = Path.of("./measurements.txt");
private static final byte COLON = ';';
private static final byte NEW_LINE = '\n';
private static final byte HYPHEN = '-';
private static final byte DOT = '.';
private static final int NO_OF_THREADS = Runtime.getRuntime().availableProcessors();
private static long[] mergeFn(final long[] v1, final long[] v2) {
v1[0] = Math.min(v1[0], v2[0]);
v1[1] = Math.max(v1[1], v2[1]);
v1[2] += v2[2];
v1[3] += v2[3];
return v1;
}
private static String toString(final Map.Entry<String, long[]> entry) {
var m = entry.getValue();
return entry.getKey()
+ '='
+ m[0] / 10.0
+ '/'
+ Math.round(1.0 * m[2] / m[3]) / 10.0
+ '/'
+ m[1] / 10.0;
}
private static Map<String, long[]> parseData(
final MemorySegment data, long offset, final long limit) {
var map = new HashMap<String, long[]>(10000, 1);
var sep = false;
var neg = false;
var key = new byte[100];
var len = 0;
var val = 0;
while (offset < limit) {
var b = data.get(JAVA_BYTE, offset++);
if (sep) {
if (b == NEW_LINE) {
val = neg ? -val : val;
map.merge(
new String(key, 0, len),
new long[]{ val, val, val, 1 },
CalculateAverage_0xshivamagarwal::mergeFn);
sep = false;
neg = false;
len = 0;
val = 0;
}
else if (b == HYPHEN) {
neg = true;
}
else if (b != DOT) {
val = val * 10 + (b - 48);
}
}
else if (b == COLON) {
sep = true;
}
else {
key[len++] = b;
}
}
return map;
}
public static void main(String[] args) throws IOException {
final String result;
try (var channel = FileChannel.open(FILE, READ);
var arena = Arena.ofShared()) {
var data = channel.map(FileChannel.MapMode.READ_ONLY, 0, channel.size(), arena);
var chunkSize = data.byteSize() / NO_OF_THREADS;
var chunks = new long[NO_OF_THREADS + 1];
chunks[NO_OF_THREADS] = data.byteSize();
for (int i = 1; i < NO_OF_THREADS; ++i) {
var chunkPos = i * chunkSize;
while (data.get(JAVA_BYTE, chunkPos++) != NEW_LINE) {
}
chunks[i] = chunkPos;
}
result = IntStream.range(0, NO_OF_THREADS)
.mapToObj(i -> parseData(data, chunks[i], chunks[i + 1]))
.parallel()
.reduce(
(m1, m2) -> {
m2.forEach((k, v) -> m1.merge(k, v, CalculateAverage_0xshivamagarwal::mergeFn));
return m1;
})
.map(
map -> map.entrySet().parallelStream()
.sorted(Map.Entry.comparingByKey())
.map(CalculateAverage_0xshivamagarwal::toString)
.collect(Collectors.joining(", ", "{", "}")))
.orElse(null);
}
System.out.println(result);
}
}
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