ddimtirov - single-threaded datastructures tuning - reading to char buffers, one pass, no allocation processing
This commit is contained in:
Dimitar Dimitrov
Gunnar Morling
parent
2458f056d6
commit
57cfa54c68
@ -15,117 +15,232 @@
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*/
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package dev.morling.onebrc;
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import java.io.BufferedReader;
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import java.io.IOException;
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import java.io.InputStreamReader;
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import java.io.*;
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import java.nio.CharBuffer;
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import java.nio.charset.StandardCharsets;
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import java.nio.file.Files;
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import java.nio.file.Path;
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import java.time.Duration;
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import java.time.Instant;
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import java.util.Map;
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import java.util.TreeMap;
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import java.util.stream.Collector;
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import static java.util.stream.Collectors.groupingByConcurrent;
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// gunnar morling - 2:10
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// roy van rijn - 1:01
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// 0:53
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// 0:37
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public class CalculateAverage_ddimtirov {
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public record InputLine(String station, int value) {
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public static InputLine fromLine(String line) {
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int endOfText = line.indexOf(";");
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String station = line.substring(0, endOfText);
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int startOfWhole = endOfText + 1;
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int sign;
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if (line.charAt(startOfWhole) == '-') {
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sign = -1;
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startOfWhole++;
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} else {
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sign = 1;
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}
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int endOfWhole = line.lastIndexOf(".");
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var whole = unsafeParsePositiveInt(line, startOfWhole, endOfWhole);
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var decimal = unsafeParsePositiveInt(line,endOfWhole+1, line.length());
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int fixpoint10 = (whole * 10 + decimal) * sign;
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return new InputLine(station, fixpoint10);
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}
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static int unsafeParsePositiveInt(String s, int start, int end) {
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int acc = 0;
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for (int i = start; i<end; i++) {
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if (acc != 0) acc *= 10;
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char c = s.charAt(i);
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var v = c - '0';
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assert v>=0 && v<=9 : String.format("Character '%s', value %,d", c, v);
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acc += v;
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}
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return acc;
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}
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}
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private static class OutputMetrics {
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private int min = Integer.MAX_VALUE;
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private int max = Integer.MIN_VALUE;
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private long sum;
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private long count;
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@SuppressWarnings("ManualMinMaxCalculation")
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public OutputMetrics combine(OutputMetrics o) {
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var r = new OutputMetrics();
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r.min = min < o.min ? min : o.min;
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r.max = max > o.max ? max : o.max;
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r.sum = sum + o.sum;
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r.count = count + o.count;
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return r;
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}
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public void accumulate(InputLine m) {
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if (m.value < min) min = m.value;
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if (m.value > max) max = m.value;
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sum += m.value;
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count++;
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}
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@Override
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public String toString() {
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var min = this.min / 10.0;
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var mean = Math.round(this.sum / (double) count) / 10.0;
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var max = this.max / 10.0;
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return min + "/" + mean + "/" + max;
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}
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}
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@SuppressWarnings("RedundantSuppression")
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public static void main(String[] args) throws IOException {
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// var start = Instant.now();
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Instant start = null;
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var path = Path.of("./measurements.txt");
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var buffer = 8192 * 20;
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var bufferSize = 512 * 64; // 64 blocks
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var tracker = new Tracker();
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var charset = StandardCharsets.UTF_8;
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// Files.lines() is optimized for files that can be indexed by int
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// For larger files it falls back to buffered reader, which we now
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// use directly to be able to tweak the buffer size.
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try (var reader = new BufferedReader(new InputStreamReader(Files.newInputStream(path)), buffer)) {
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var stationsToMetrics = reader.lines()
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.map(InputLine::fromLine)
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.parallel()
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.collect(groupingByConcurrent(InputLine::station, Collector.of(
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OutputMetrics::new,
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OutputMetrics::accumulate,
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OutputMetrics::combine,
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OutputMetrics::toString
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)));
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System.out.println(new TreeMap<>(stationsToMetrics));
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assert Files.readAllLines(Path.of("expected_result.txt")).getFirst().equals(new TreeMap<>(stationsToMetrics).toString());
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try (var stream = Files.newInputStream(path); var reader = new InputStreamReader(stream, charset)) {
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var buffered = new RecordReader(reader, bufferSize);
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InputRecord record = null;
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while (true) {
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record = buffered.readRecord(record);
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if (record==null) break;
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tracker.process(record);
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}
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}
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System.out.println(tracker.stationsToMetrics());
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//noinspection ConstantValue
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if (start!=null) System.err.println(Duration.between(start, Instant.now()));
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assert Files.readAllLines(Path.of("expected_result.txt")).getFirst().equals(tracker.stationsToMetrics().toString());
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}
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/**
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* <p>Reads records we can use to do the filtering from a stream of characters.
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* Takes care of framing, and I/O buffering.
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* This class in combination with {@link RecordReader} allows us to fully hide the
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* I/O and internal representation.
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*
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* <p>If used with recycled {@link InputRecord} instances, this class allocates no memory
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* after instantiation. The class is stateful, and the internals are not threadsafe
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* - use from single thread or with proper synchronization.
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*/
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static class RecordReader {
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/**
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* The source of input data
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*/
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private final Readable input;
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/**
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* Used for i/o buffering and record parsing.
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* @see #buf
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*/
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private final CharBuffer buffer;
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/**
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* <p>Cached backing array from {@link #buffer}.
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* <p>This is optimization because {@link CharBuffer#array()} was showing on the CPU profile.
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*/
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private final char[] buf;
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public RecordReader(Readable input, int bufferSize) {
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this.input = input;
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buffer = CharBuffer.allocate(bufferSize).flip();
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buf = buffer.array();
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}
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public InputRecord readRecord(InputRecord recycled) throws IOException {
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var record = parseRecord(recycled);
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if (record!=null) return record;
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if (input.read(buffer.compact())==-1) return null;
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buffer.flip();
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return parseRecord(recycled);
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}
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private InputRecord parseRecord(InputRecord recycled) {
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var lim = buffer.limit();
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if (buffer.isEmpty()) return null;
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var nameOff = buffer.position();
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var buff = buf;
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while (buff[nameOff]=='\n' || buff[nameOff]=='\r' || buff[nameOff]==' ' ) {
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nameOff++;
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if (nameOff>=lim) return null;
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}
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var nameHash = 0;
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var nameLen = 0;
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while (buff[nameOff+nameLen]!=';') {
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nameHash = nameHash*31 + buff[nameOff+nameLen];
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nameLen++;
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if (nameOff+nameLen>=lim) return null;
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}
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//noinspection DuplicateExpressions
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assert new String(buf, nameOff, nameLen).hashCode()==nameHash
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: "'%s'@%d !-> %d".formatted(new String(buf, nameOff, nameLen), new String(buf, nameOff, nameLen).hashCode(), nameHash);
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var valCursor = nameOff + nameLen +1;
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int signum = 1;
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var acc = 0;
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while (true) {
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if (valCursor >= lim) {
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return null;
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}
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char c = buff[valCursor++];
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if (c == '\n' || c == '\r') {
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break;
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}
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if (c=='.') continue;
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if (acc == 0) {
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if (c == '-') {
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signum = -1;
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continue;
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}
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} else {
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acc *= 10;
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}
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var v = c - '0';
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assert v>=0 && v<=9 : String.format("Character '%s', value %,d", c, v);
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acc += v;
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}
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buffer.position(valCursor);
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var record = recycled!=null ? recycled : new InputRecord(buf);
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record.init(nameHash, nameOff, nameLen, acc*signum);
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return record;
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}
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}
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static class Tracker {
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private static final int ADDRESS_NO_CLASH_MODULUS = 49999;
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private static final int OFFSET_MIN = 0;
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private static final int OFFSET_MAX = 1;
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private static final int OFFSET_COUNT = 2;
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private final int[] minMaxCount = new int[ADDRESS_NO_CLASH_MODULUS * 3];
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private final long[] sums = new long[ADDRESS_NO_CLASH_MODULUS];
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private final String[] names = new String[ADDRESS_NO_CLASH_MODULUS];
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public void process(InputRecord r) {
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var i = Math.abs(r.nameHash) % ADDRESS_NO_CLASH_MODULUS;
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if (names[i]==null) names[i] = r.name();
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sums[i] += r.value;
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int mmcIndex = i * 3;
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var min = minMaxCount[mmcIndex + OFFSET_MIN];
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var max = minMaxCount[mmcIndex + OFFSET_MAX];
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if (r.value < min) minMaxCount[mmcIndex + OFFSET_MIN] = r.value;
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if (r.value > max) minMaxCount[mmcIndex + OFFSET_MAX] = r.value;
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minMaxCount[mmcIndex + OFFSET_COUNT]++;
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}
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public Map<String, String> stationsToMetrics() {
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var m = new TreeMap<String, String>();
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for (int i = 0; i < names.length; i++) {
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var name = names[i];
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if (name==null) continue;
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var min = minMaxCount[i*3] / 10.0;
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var max = minMaxCount[i*3+1] / 10.0;
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var count = minMaxCount[i*3+2];
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var sum = sums[i];
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var mean = Math.round((double) sum / count) / 10.0;
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m.put(name, min + "/" + mean + "/" + max);
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}
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return m;
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}
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}
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static class InputRecord {
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private final char[] chars;
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private int idOffset;
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private int idLength;
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public int value; // fixpoint scaled by 10
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public int nameHash;
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public InputRecord(char[] chars) {
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this.chars = chars;
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}
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public void init(int nameHash, int nameOffset, int nameLength, int fixpointValue) {
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assert nameOffset+nameLength<chars.length : String.format("idOffset+idLength=%d < chars.length=%d", nameOffset+nameLength, chars.length);
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this.idOffset = nameOffset;
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this.idLength = nameLength;
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this.value = fixpointValue;
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this.nameHash = nameHash;
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}
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public String name() {
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return new String(chars, idOffset, idLength);
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}
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@Override
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public String toString() {
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return name() + ";" + (value / 10.0);
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}
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}
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}
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