diff --git a/calculate_average_seijikun.sh b/calculate_average_seijikun.sh
new file mode 100755
index 0000000..fbe68ad
--- /dev/null
+++ b/calculate_average_seijikun.sh
@@ -0,0 +1,20 @@
+#!/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.
+#
+
+
+JAVA_OPTS="--enable-preview"
+time java $JAVA_OPTS --class-path target/average-1.0.0-SNAPSHOT.jar dev.morling.onebrc.CalculateAverage_seijikun
diff --git a/src/main/java/dev/morling/onebrc/CalculateAverage_seijikun.java b/src/main/java/dev/morling/onebrc/CalculateAverage_seijikun.java
new file mode 100644
index 0000000..8038c1a
--- /dev/null
+++ b/src/main/java/dev/morling/onebrc/CalculateAverage_seijikun.java
@@ -0,0 +1,221 @@
+/*
+ *  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.*;
+import java.nio.MappedByteBuffer;
+import java.nio.channels.FileChannel;
+import java.util.TreeMap;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+
+public class CalculateAverage_seijikun {
+
+    private static final String FILE = "./measurements.txt";
+
+
+    private static class MeasurementAggregator {
+        private double min = Double.POSITIVE_INFINITY;
+        private double max = Double.NEGATIVE_INFINITY;
+        private double sum;
+        private long count;
+
+        public void printInto(PrintStream out) {
+            out.printf("%.1f/%.1f/%.1f", min, (sum / (double) count), max);
+        }
+    }
+
+    public static class StationIdent implements Comparable<StationIdent> {
+        private final int nameLength;
+        private final String name;
+        private final int nameHash;
+
+        public StationIdent(byte[] name, int nameHash) {
+            this.nameLength = name.length;
+            this.name = new String(name);
+            this.nameHash = nameHash;
+        }
+
+        @Override
+        public int hashCode() {
+            return nameHash;
+        }
+
+        @Override
+        public boolean equals(Object obj) {
+            var other = (StationIdent) obj;
+            if (other.nameLength != nameLength) {
+                return false;
+            }
+            return name.equals(other.name);
+        }
+
+        @Override
+        public int compareTo(StationIdent o) {
+            return name.compareTo(o.name);
+        }
+    }
+
+    public static class ChunkReader implements Runnable {
+        RandomAccessFile file;
+
+        // Start offset of this chunk
+        private final long startOffset;
+        // end offset of this chunk
+        private final long endOffset;
+
+        // state
+        private MappedByteBuffer buffer = null;
+        private int ptr = 0;
+        private TreeMap<StationIdent, MeasurementAggregator> workSet;
+
+        public ChunkReader(RandomAccessFile file, long startOffset, long endOffset) {
+            this.file = file;
+            this.startOffset = startOffset;
+            this.endOffset = endOffset;
+        }
+
+        private StationIdent readStationName() {
+            int startPtr = ptr;
+            int hashCode = 0;
+            int hashBytePtr = 0;
+            byte c;
+            while ((c = buffer.get(ptr++)) != ';') {
+                hashCode ^= ((int) c) << (hashBytePtr * 8);
+                hashBytePtr = (hashBytePtr + 1) % 4;
+            }
+            byte[] stationNameBfr = new byte[ptr - startPtr - 1];
+            buffer.get(startPtr, stationNameBfr);
+            return new StationIdent(stationNameBfr, hashCode);
+        }
+
+        private double readTemperature() {
+            double ret = 0, div = 1;
+            byte c = buffer.get(ptr++);
+            boolean neg = (c == '-');
+            if (neg)
+                c = buffer.get(ptr++);
+
+            do {
+                ret = ret * 10 + c - '0';
+            } while ((c = buffer.get(ptr++)) >= '0' && c <= '9');
+
+            if (c == '.') {
+                while ((c = buffer.get(ptr++)) != '\n') {
+                    ret += (c - '0') / (div *= 10);
+                }
+            }
+
+            if (neg)
+                return -ret;
+            return ret;
+        }
+
+        @Override
+        public void run() {
+            workSet = new TreeMap<>();
+            int chunkSize = (int) (endOffset - startOffset);
+            try {
+                buffer = file.getChannel().map(FileChannel.MapMode.READ_ONLY, startOffset, chunkSize);
+
+                while (ptr < chunkSize) {
+                    var station = readStationName();
+                    var temp = readTemperature();
+                    var stationWorkSet = workSet.get(station);
+                    if (stationWorkSet == null) {
+                        stationWorkSet = new MeasurementAggregator();
+                        workSet.put(station, stationWorkSet);
+                    }
+                    stationWorkSet.min = Math.min(temp, stationWorkSet.min);
+                    stationWorkSet.max = Math.max(temp, stationWorkSet.max);
+                    stationWorkSet.sum += temp;
+                    stationWorkSet.count += 1;
+                }
+            }
+            catch (IOException e) {
+                e.printStackTrace();
+                throw new RuntimeException(e);
+            }
+        }
+    }
+
+    public static void main(String[] args) throws IOException, InterruptedException {
+        RandomAccessFile file = new RandomAccessFile(FILE, "r");
+
+        int jobCnt = Runtime.getRuntime().availableProcessors();
+
+        var chunks = new ChunkReader[jobCnt];
+        long chunkSize = file.length() / jobCnt;
+        long chunkStartPtr = 0;
+        byte[] tmpBuffer = new byte[128];
+        for (int i = 0; i < jobCnt; ++i) {
+            long chunkEndPtr = chunkStartPtr + chunkSize;
+            if (i != (jobCnt - 1)) { // align chunks to newlines
+                file.seek(chunkEndPtr - 1);
+                file.read(tmpBuffer);
+                int offset = 0;
+                while (tmpBuffer[offset] != '\n') {
+                    offset += 1;
+                }
+                chunkEndPtr += offset;
+            }
+            else { // last chunk ends at file end
+                chunkEndPtr = file.length();
+            }
+            chunks[i] = new ChunkReader(file, chunkStartPtr, chunkEndPtr);
+            chunkStartPtr = chunkEndPtr;
+        }
+
+        try(var executor = Executors.newFixedThreadPool(jobCnt)) {
+            for (int i = 0; i < jobCnt; ++i) {
+                executor.submit(chunks[i]);
+            }
+            executor.shutdown();
+            var ignored = executor.awaitTermination(1, TimeUnit.DAYS);
+        }
+
+        // merge chunks
+        var result = chunks[0].workSet;
+        for (int i = 1; i < jobCnt; ++i) {
+            chunks[i].workSet.forEach((ident, otherStationWorkSet) -> {
+                var stationWorkSet = result.get(ident);
+                if (stationWorkSet == null) {
+                    result.put(ident, otherStationWorkSet);
+                }
+                else {
+                    stationWorkSet.min = Math.min(stationWorkSet.min, otherStationWorkSet.min);
+                    stationWorkSet.max = Math.max(stationWorkSet.max, otherStationWorkSet.max);
+                    stationWorkSet.sum += otherStationWorkSet.sum;
+                    stationWorkSet.count += otherStationWorkSet.count;
+                }
+            });
+        }
+
+        // print in required format
+        System.out.write('{');
+        var iterator = result.entrySet().iterator();
+        while (iterator.hasNext()) {
+            var entry = iterator.next();
+            System.out.print(entry.getKey().name);
+            System.out.write('=');
+            entry.getValue().printInto(System.out);
+            if (iterator.hasNext()) {
+                System.out.print(", ");
+            }
+        }
+        System.out.println('}');
+    }
+}