use custom container (#305)

src/main/java/dev/morling/onebrc/CalculateAverage_zerninv.java

@@ -24,7 +24,6 @@ import java.util.*;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.Executors;
 import java.util.concurrent.Future;
-import java.util.stream.Collectors;
 
 public class CalculateAverage_zerninv {
     private static final String FILE = "./measurements.txt";
@@ -91,9 +90,9 @@ public class CalculateAverage_zerninv {
     }
 
     private static Map<String, MeasurementAggregation> calcForChunk(FileChannel channel, long begin, long end) throws IOException {
-        var results = new HashMap<CityWrapper, MeasurementAggregation>(10_000);
         var mbb = channel.map(FileChannel.MapMode.READ_ONLY, begin, end - begin);
-        int cityOffset, hashCode, temperatureOffset, temperature;
+        var results = new MeasurementContainer(mbb);
+        int cityOffset, cityNameSize, hashCode, temperatureOffset, temperature;
         byte b;
 
         while (mbb.hasRemaining()) {
@@ -104,7 +103,7 @@ public class CalculateAverage_zerninv {
             }
 
             temperatureOffset = mbb.position();
-            CityWrapper city = new CityWrapper(mbb, cityOffset, temperatureOffset - cityOffset - 1, hashCode);
+            cityNameSize = temperatureOffset - cityOffset - 1;
 
             temperature = 0;
             while ((b = mbb.get()) != LINE_SEPARATOR) {
@@ -115,32 +114,22 @@ public class CalculateAverage_zerninv {
             if (mbb.get(temperatureOffset) == MINUS) {
                 temperature *= -1;
             }
-
+            results.put(cityOffset, cityNameSize, hashCode, (short) temperature);
-            var result = results.get(city);
-            if (result != null) {
-                result.addTemperature(temperature);
         }
-            else {
+        return results.toStringMap();
-                results.put(city, new MeasurementAggregation().addTemperature(temperature));
-            }
-        }
-        return results.entrySet()
-                .stream()
-                .collect(Collectors.toMap(entry -> entry.getKey().toString(), Map.Entry::getValue));
     }
 
     private static final class MeasurementAggregation {
         private long sum;
         private int count;
-        private int min = Integer.MAX_VALUE;
+        private short min;
-        private int max = Integer.MIN_VALUE;
+        private short max;
 
-        public MeasurementAggregation addTemperature(int temperature) {
+        public MeasurementAggregation(long sum, int count, short min, short max) {
-            sum += temperature;
+            this.sum = sum;
-            count++;
+            this.count = count;
-            min = Math.min(temperature, min);
+            this.min = min;
-            max = Math.max(temperature, max);
+            this.max = max;
-            return this;
         }
 
         public void merge(MeasurementAggregation o) {
@@ -149,8 +138,8 @@ public class CalculateAverage_zerninv {
             }
             sum += o.sum;
             count += o.count;
-            min = Math.min(min, o.min);
+            min = min < o.min ? min : o.min;
-            max = Math.max(max, o.max);
+            max = max > o.max ? max : o.max;
         }
 
         @Override
@@ -159,39 +148,77 @@ public class CalculateAverage_zerninv {
         }
     }
 
-    private record CityWrapper(MappedByteBuffer mbb, int begin, int size, int hash) {
+    private static final class MeasurementContainer {
+        private static final int SIZE = 1024 * 16;
 
-        @Override
+        private final MappedByteBuffer mbb;
-        public boolean equals(Object o) {
+        private final int[] offsets = new int[SIZE];
-            if (this == o) {
+        private final int[] sizes = new int[SIZE];
-                return true;
+        private final int[] hashes = new int[SIZE];
-            }
+
-            if (o == null || getClass() != o.getClass()) {
+        private final long[] sums = new long[SIZE];
-                return false;
+        private final int[] counts = new int[SIZE];
+        private final short[] mins = new short[SIZE];
+        private final short[] maxs = new short[SIZE];
+
+        private MeasurementContainer(MappedByteBuffer mbb) {
+            this.mbb = mbb;
+            Arrays.fill(mins, Short.MAX_VALUE);
+            Arrays.fill(maxs, Short.MIN_VALUE);
         }
 
-            CityWrapper that = (CityWrapper) o;
+        public void put(int offset, int size, int hash, short value) {
-            if (hash != that.hash || size != that.size) {
+            int i = findIdx(offset, size, hash);
-                return false;
+            offsets[i] = offset;
+            sizes[i] = size;
+            hashes[i] = hash;
+
+            sums[i] += value;
+            counts[i]++;
+
+            if (value < mins[i]) {
+                mins[i] = value;
             }
-            for (int i = 0; i < size; i++) {
+            if (value > maxs[i]) {
-                if (mbb.get(begin + i) != mbb.get(that.begin + i)) {
+                maxs[i] = value;
+            }
+        }
+
+        public Map<String, MeasurementAggregation> toStringMap() {
+            var result = new HashMap<String, MeasurementAggregation>();
+            for (int i = 0; i < SIZE; i++) {
+                if (counts[i] != 0) {
+                    var key = createString(offsets[i], sizes[i]);
+                    result.put(key, new MeasurementAggregation(sums[i], counts[i], mins[i], maxs[i]));
+                }
+            }
+            return result;
+        }
+
+        private int findIdx(int offset, int size, int hash) {
+            int i = Math.abs(hash % SIZE);
+            while (counts[i] != 0) {
+                if (hashes[i] == hash && sizes[i] == size && isEqual(i, offset)) {
+                    break;
+                }
+                i = (i + 1) % SIZE;
+            }
+            return i;
+        }
+
+        private boolean isEqual(int index, int offset) {
+            for (int i = 0; i < sizes[index]; i++) {
+                if (mbb.get(offsets[index] + i) != mbb.get(offset + i)) {
                     return false;
                 }
             }
             return true;
         }
 
-        @Override
+        private String createString(int offset, int size) {
-        public int hashCode() {
-            return hash;
-        }
-
-        @Override
-        public String toString() {
             byte[] arr = new byte[size];
             for (int i = 0; i < size; i++) {
-                arr[i] = mbb.get(begin + i);
+                arr[i] = mbb.get(offset + i);
             }
             return new String(arr);
         }