diff --git a/calculate_average_deemkeen.sh b/calculate_average_deemkeen.sh
new file mode 100755
index 0000000..036f850
--- /dev/null
+++ b/calculate_average_deemkeen.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_deemkeen
diff --git a/src/main/java/dev/morling/onebrc/CalculateAverage_deemkeen.java b/src/main/java/dev/morling/onebrc/CalculateAverage_deemkeen.java
new file mode 100644
index 0000000..f6d66fb
--- /dev/null
+++ b/src/main/java/dev/morling/onebrc/CalculateAverage_deemkeen.java
@@ -0,0 +1,264 @@
+/*
+ *  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.File;
+import java.io.IOException;
+import java.io.RandomAccessFile;
+import java.nio.MappedByteBuffer;
+import java.nio.channels.FileChannel;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.StandardOpenOption;
+import java.util.*;
+import java.util.concurrent.*;
+
+public class CalculateAverage_deemkeen {
+    private static final String FILE = "./measurements.txt";
+
+    public static void main(String[] args) throws IOException, ExecutionException, InterruptedException {
+
+        File file = new File(FILE);
+        long fileSize = file.length();
+        int numberOfSegments = 400;
+        long segmentSize = fileSize / numberOfSegments;
+
+        if (segmentSize < 100) {
+            numberOfSegments = 1;
+            segmentSize = fileSize;
+        }
+
+        List<SegmentPair> segments = new ArrayList<>();
+
+        try (
+                var randomAccessFile = new RandomAccessFile(file, "r");
+                var fileChannel = (FileChannel) Files.newByteChannel(Path.of(FILE), StandardOpenOption.READ)) {
+            for (int i = 0; i < numberOfSegments; i++) {
+                long segStart = i * segmentSize;
+                long segEnd = (i == numberOfSegments - 1) ? fileSize : segStart + segmentSize;
+
+                if (i != 0) {
+                    randomAccessFile.seek(segStart);
+                    while (segStart < segEnd) {
+                        segStart++;
+                        if (randomAccessFile.read() == '\n')
+                            break;
+                    }
+                }
+
+                if (i != numberOfSegments - 1) {
+                    randomAccessFile.seek(segEnd);
+                    while (segEnd < fileSize) {
+                        segEnd++;
+                        if (randomAccessFile.read() == '\n')
+                            break;
+                    }
+                }
+
+                segments.add(new SegmentPair(new FileSegment(segStart, segEnd), new ByteArrayToResultMap()));
+            }
+
+            try (ExecutorService es = Executors.newVirtualThreadPerTaskExecutor()) {
+                var partitions = Collections.synchronizedList(new ArrayList<ByteArrayToResultMap>());
+                for (var segment : segments) {
+                    var segmentResultMap = segment.value;
+                    es.execute(() -> {
+                        MappedByteBuffer bb;
+                        try {
+                            bb = fileChannel.map(FileChannel.MapMode.READ_ONLY, segment.key.start, segment.key.end - segment.key.start);
+                        }
+                        catch (IOException e) {
+                            throw new RuntimeException(e);
+                        }
+                        byte[] buffer = new byte[100];
+                        int startLine;
+                        while ((startLine = bb.position()) < bb.limit()) {
+                            int currentPosition = startLine;
+                            byte b;
+                            int offset = 0;
+                            int hash = 0;
+                            while (currentPosition != segment.key.end && (b = bb.get(currentPosition++)) != ';') {
+                                buffer[offset++] = b;
+                                hash = 31 * hash + b;
+                            }
+                            int temp;
+                            int negative = 1;
+                            // Inspired by @yemreinci to unroll this even further
+                            if (bb.get(currentPosition) == '-') {
+                                negative = -1;
+                                currentPosition++;
+                            }
+                            if (bb.get(currentPosition + 1) == '.') {
+                                temp = negative * ((bb.get(currentPosition) - '0') * 10 + (bb.get(currentPosition + 2) - '0'));
+                                currentPosition += 3;
+                            }
+                            else {
+                                temp = negative
+                                        * ((bb.get(currentPosition) - '0') * 100 + ((bb.get(currentPosition + 1) - '0') * 10 + (bb.get(currentPosition + 3) - '0')));
+                                currentPosition += 4;
+                            }
+                            if (bb.get(currentPosition) == '\r') {
+                                currentPosition++;
+                            }
+                            currentPosition++;
+                            segmentResultMap.putOrMerge(buffer, 0, offset, temp / 10.0, hash);
+                            bb.position(currentPosition);
+                        }
+
+                    });
+
+                    partitions.add(segmentResultMap);
+
+                }
+
+                try {
+                    es.shutdown();
+                    while (!es.awaitTermination(24L, TimeUnit.HOURS)) {
+                        System.out.println("Still waiting for termination..");
+                    }
+                }
+                catch (InterruptedException e) {
+                    // do nothing
+                }
+
+                TreeMap<String, Result> resultMap = new TreeMap<>();
+                for (ByteArrayToResultMap partition : partitions) {
+                    for (Entry e : partition.getAll()) {
+                        resultMap.merge(new String(e.key()), e.value(), CalculateAverage_deemkeen::merge);
+                    }
+                }
+
+                System.out.println(resultMap);
+            }
+        }
+    }
+
+    private static Result merge(Result v, Result value) {
+        return merge(v, value.min, value.max, value.sum, value.count);
+    }
+
+    private static Result merge(Result v, double value, double value1, double value2, long value3) {
+        v.min = Math.min(v.min, value);
+        v.max = Math.max(v.max, value1);
+        v.sum += value2;
+        v.count += value3;
+        return v;
+    }
+
+    record Pair(int slot, Result slotValue) {
+    }
+
+    record SegmentPair(FileSegment key, ByteArrayToResultMap value) {
+    }
+
+    record Entry(byte[] key, Result value) {
+    }
+
+    record FileSegment(long start, long end) {
+    }
+
+    static class Result {
+        double min;
+        double max;
+        double sum;
+        long count;
+
+        Result(double value) {
+            this.min = value;
+            this.max = value;
+            this.sum = value;
+            this.count = 1;
+        }
+
+        @Override
+        public String toString() {
+            return round(min) +
+                    "/" + round(sum / count) +
+                    "/" + round(max);
+        }
+
+        double round(double v) {
+            return Math.round(v * 10.0) / 10.0;
+        }
+
+    }
+
+    static class ByteArrayToResultMap {
+        public static final int MAPSIZE = 1024 * 128;
+        Result[] slots = new Result[MAPSIZE];
+        byte[][] keys = new byte[MAPSIZE][];
+
+        public void putOrMerge(byte[] key, int offset, int size, double temp, int hash) {
+            int slot = hash & (slots.length - 1);
+            var slotValue = slots[slot];
+            // Linear probe for open slot
+            while (slotValue != null && (keys[slot].length != size || !Arrays.equals(keys[slot], 0, size, key, offset, size))) {
+                slot = (slot + 1) & (slots.length - 1);
+                slotValue = slots[slot];
+            }
+            Result value = slotValue;
+            if (value == null) {
+                slots[slot] = new Result(temp);
+                byte[] bytes = new byte[size];
+                System.arraycopy(key, offset, bytes, 0, size);
+                keys[slot] = bytes;
+            }
+            else {
+                value.min = Math.min(value.min, temp);
+                value.max = Math.max(value.max, temp);
+                value.sum += temp;
+                value.count += 1;
+            }
+        }
+
+        private int hashCode(byte[] a, int fromIndex, int length) {
+            int result = 0;
+            int end = fromIndex + length;
+            for (int i = fromIndex; i < end; i++) {
+                result = 31 * result + a[i];
+            }
+            return result;
+        }
+
+        private Pair getPair(byte[] key, int offset, int size) {
+            int hash = hashCode(key, offset, size);
+            int slot = hash & (slots.length - 1);
+            Result slotValue = slots[slot];
+            // Linear probe for open slot
+            while (slotValue != null && (keys[slot].length != size || !Arrays.equals(keys[slot], 0, size, key, offset, size))) {
+                slot = (slot + 1) & (slots.length - 1);
+                slotValue = slots[slot];
+            }
+            return new Pair(slot, slotValue);
+        }
+
+        public Result get(byte[] key, int offset, int size) {
+            return getPair(key, offset, size).slotValue();
+        }
+
+        // Get all pairs
+        public List<Entry> getAll() {
+            List<Entry> result = new ArrayList<>();
+            for (int i = 0; i < slots.length; i++) {
+                Result slotValue = slots[i];
+                if (slotValue != null) {
+                    result.add(new Entry(keys[i], slotValue));
+                }
+            }
+            return result;
+        }
+    }
+}
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