Entry for abhinav-upadhyay

calculate_average_abhinav-upadhyay.sh

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+#!/bin/sh
+#
+#  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.
+#
+
+# Uncomment below to use sdk
+# source "$HOME/.sdkman/bin/sdkman-init.sh"
+# sdk use java 21.0.1-graal 1>&2
+
+JAVA_OPTS="--enable-preview"
+java $JAVA_OPTS --class-path target/average-1.0.0-SNAPSHOT.jar dev.morling.onebrc.CalculateAverage_abhinavupadhyay

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

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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 sun.misc.Unsafe;
+
+import java.io.IOException;
+import java.lang.foreign.Arena;
+import java.lang.reflect.Field;
+import java.nio.channels.FileChannel;
+import java.nio.file.Paths;
+import java.nio.file.StandardOpenOption;
+import java.util.Arrays;
+import java.util.List;
+import java.util.Map;
+import java.util.TreeMap;
+
+public class CalculateAverage_abhinavupadhyay {
+
+    private static final String FILE_NAME = "./measurements.txt";
+
+    private static Unsafe initUnsafe() {
+        try {
+            final Field theUnsafe = Unsafe.class.getDeclaredField("theUnsafe");
+            theUnsafe.setAccessible(true);
+            return (Unsafe) theUnsafe.get(Unsafe.class);
+        }
+        catch (NoSuchFieldException | IllegalAccessException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    private final static Unsafe UNSAFE = initUnsafe();
+
+    public static final long HASSEMI = 0x3B3B3B3B3B3B3B3BL;
+
+    static long has0(long x) {
+        return (x - 0x0101010101010101L) & (~x) & 0x8080808080808080L;
+    }
+
+    private static class Table {
+        private static final int TABLE_SIZE = 1 << 21; // 0x8000; // collisions with table smaller than this. Need a better hash function
+        private static final int TABLE_MASK = TABLE_SIZE - 1;
+        Row[] table = new Row[TABLE_SIZE];
+        byte[] array = new byte[256];
+
+        public void put(long cityStartOffset, long cityLength, long nameHash, int temperature) {
+            final long uhash = nameHash ^ (nameHash >> 29);
+            // final long uhash = nameHash;
+            int index = (int) uhash & TABLE_MASK;
+            Row row = table[index];
+            if (row == null) {
+                int i = 0;
+                for (; i < cityLength - 1;) {
+                    array[i++] = UNSAFE.getByte(cityStartOffset++);
+                    array[i++] = UNSAFE.getByte(cityStartOffset++);
+                }
+                for (; i < cityLength; i++) {
+                    array[i] = UNSAFE.getByte(cityStartOffset++);
+                }
+                table[index] = new Row(new String(array, 0, i), temperature, temperature, 1, temperature, (int) uhash);
+                return;
+            }
+
+            row.update(temperature);
+
+        }
+
+    }
+
+    private static final class Row {
+        private final String name;
+        private int minTemp;
+        private int maxTemp;
+        private int count;
+        private int sum;
+        private final long hash;
+
+        public Row(String name, int minTemp, int maxTemp, int count, int sum, long hash) {
+            this.name = name;
+            this.minTemp = minTemp;
+            this.maxTemp = maxTemp;
+            this.count = count;
+            this.sum = sum;
+            this.hash = hash;
+        }
+
+        void update(int temperature) {
+            this.count++;
+            this.sum += temperature;
+            if (temperature < minTemp) {
+                this.minTemp = temperature;
+                return;
+            }
+            if (temperature > maxTemp) {
+                this.maxTemp = temperature;
+            }
+        }
+
+        @Override
+        public String toString() {
+            return String.format("%.1f/%.1f/%.1f", this.minTemp / 10.0, this.sum / (count * 10.0), maxTemp / 10.0);
+        }
+
+        public Row update(Row value) {
+            this.minTemp = Integer.min(this.minTemp, value.minTemp);
+            this.maxTemp = Integer.max(this.maxTemp, value.maxTemp);
+            this.count += value.count;
+            this.sum += value.sum;
+            return this;
+        }
+
+        @Override
+        public boolean equals(Object obj) {
+            if (obj == this)
+                return true;
+            if (obj == null || obj.getClass() != this.getClass())
+                return false;
+            return this.hash == ((Row) obj).hash;
+        }
+
+        @Override
+        public int hashCode() {
+            return (int) this.hash;
+        }
+
+        private static int max(int a, int b) {
+            a -= b;
+            a &= (~a) >> 31;
+            return a + b;
+        }
+
+        private static int min(int a, int b) {
+            a -= b;
+            a &= a >> 31;
+            return a + b;
+        }
+
+    }
+
+    private static Table readFile(long startAddress, long endAddress) {
+        Table table = new Table();
+        long currentOffset = startAddress;
+        long nameHash = 1;
+        while (currentOffset < endAddress) {
+            long cityStart = currentOffset;
+            long word = UNSAFE.getLong(currentOffset);
+            long hasSemi = has0(word ^ HASSEMI);
+            while (hasSemi == 0) {
+                currentOffset += 8;
+                for (int i = 0; i < 8; i++) {
+                    byte b = (byte) ((word >> (i * 8)) & 0xff);
+                    nameHash = nameHash * 31 + b;
+                    nameHash += (nameHash << 10);
+                    nameHash ^= (nameHash >> 6);
+                }
+                word = UNSAFE.getLong(currentOffset);
+                hasSemi = has0(word ^ HASSEMI);
+            }
+            int trailingZeros = Long.numberOfTrailingZeros(hasSemi);
+            int semiColonIndex = trailingZeros >> 3;
+            if (trailingZeros >= 8) {
+                int nonZeroBits = 64 - trailingZeros;
+                nameHash ^= ((word << nonZeroBits) >> nonZeroBits);
+                nameHash += (nameHash << 10);
+                nameHash ^= (nameHash >> 6);
+                currentOffset += semiColonIndex;
+            }
+            long cityLength = currentOffset - cityStart;
+            currentOffset++; // skip ;
+            int temperature = 0;
+            int scale = 1;
+            int isNegative = 1;
+            byte b = UNSAFE.getByte(currentOffset++);
+            if (b == '-') {
+                isNegative = -1;
+            }
+            else {
+                temperature = b - '0';
+                scale = 10;
+            }
+            while ((b = UNSAFE.getByte(currentOffset++)) != '\n') {
+                if (b == '.') {
+                    continue;
+                }
+                temperature = temperature * scale + b - '0';
+                scale = 10;
+            }
+            temperature *= isNegative;
+            table.put(cityStart, cityLength, nameHash, temperature);
+            nameHash = 1;
+        }
+        return table;
+
+    }
+
+    public static void main(String[] args) throws IOException {
+        String filename = args.length > 0 ? args[0] : FILE_NAME;
+        FileChannel fc = FileChannel.open(Paths.get(filename), StandardOpenOption.READ);
+        final long fileSize = fc.size();
+        final long startAddress = fc.map(FileChannel.MapMode.READ_ONLY, 0, fileSize, Arena.global()).address();
+        final long endAddress = startAddress + fileSize;
+        final long[][] segments = findSegments(startAddress, endAddress, fileSize, fileSize > 1024 * 1024 * 1024 ? 8 : 1);
+        final List<Table> collect = Arrays.stream(segments).parallel().map(s -> readFile(s[0], s[1])).toList();
+        Map<String, Row> finalMap = new TreeMap<>();
+        for (final Table t : collect) {
+            for (int j = 0; j < Table.TABLE_SIZE; j++) {
+                final Row row = t.table[j];
+                if (row == null) {
+                    continue;
+                }
+                finalMap.compute(row.name, (_, v) -> v == null ? row : v.update(row));
+            }
+        }
+        System.out.println(finalMap);
+    }
+
+    private static long[][] findSegments(long startAddress, long endAddress, long size, int segmentCount) {
+        if (segmentCount == 1) {
+            return new long[][]{ { startAddress, endAddress } };
+        }
+        long[][] segments = new long[segmentCount][2];
+        long segmentSize = size / segmentCount + 1;
+        int i = 0;
+        long currentOffset = startAddress;
+        while (currentOffset < endAddress) {
+            segments[i][0] = currentOffset;
+            currentOffset += segmentSize;
+            currentOffset = Math.min(currentOffset, endAddress);
+            if (currentOffset >= endAddress) {
+                segments[i][1] = endAddress;
+                break;
+            }
+            while (UNSAFE.getByte(currentOffset) != '\n') {
+                currentOffset++;
+                // align to newline boundary
+            }
+            segments[i++][1] = currentOffset++;
+        }
+        return segments;
+    }
+}