Use Arena MemorySegments rather than ByteBuffers. (#505)

calculate_average_ebarlas.sh

@@ -15,5 +15,5 @@
 #  limitations under the License.
 #
 
-JAVA_OPTS=""
+JAVA_OPTS="--enable-preview"
 java $JAVA_OPTS --class-path target/average-1.0.0-SNAPSHOT.jar dev.morling.onebrc.CalculateAverage_ebarlas

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

@@ -18,9 +18,9 @@ package dev.morling.onebrc;
 import sun.misc.Unsafe;
 
 import java.io.IOException;
-import java.nio.BufferUnderflowException;
+import java.lang.foreign.Arena;
-import java.nio.ByteBuffer;
+import java.lang.foreign.MemorySegment;
-import java.nio.ByteOrder;
+import java.lang.foreign.ValueLayout;
 import java.nio.channels.FileChannel;
 import java.nio.charset.StandardCharsets;
 import java.nio.file.Paths;
@@ -30,9 +30,13 @@ import java.util.TreeMap;
 
 public class CalculateAverage_ebarlas {
 
+    private static final Arena ARENA = Arena.global();
+
     private static final int MAX_KEY_SIZE = 100;
+    private static final int MAX_VAL_SIZE = 5; // -dd.d
+    private static final int MAX_LINE_SIZE = MAX_KEY_SIZE + MAX_VAL_SIZE + 2; // key, semicolon, val, newline
     private static final int HASH_FACTOR = 433;
-    private static final int HASH_TBL_SIZE = 16_383; // range of allowed hash values, inclusive
+    private static final int HASH_TBL_SIZE = 32_767; // range of allowed hash values, inclusive
 
     private static final Unsafe UNSAFE = makeUnsafe();
 
@@ -50,7 +54,7 @@ public class CalculateAverage_ebarlas {
     public static void main(String[] args) throws IOException, InterruptedException {
         var path = Paths.get("measurements.txt");
         var channel = FileChannel.open(path, StandardOpenOption.READ);
-        var numPartitions = (int) Math.max((channel.size() / Integer.MAX_VALUE) + 1, Runtime.getRuntime().availableProcessors());
+        var numPartitions = Runtime.getRuntime().availableProcessors();
         var partitionSize = channel.size() / numPartitions;
         var partitions = new Partition[numPartitions];
         var threads = new Thread[numPartitions];
@@ -63,8 +67,8 @@ public class CalculateAverage_ebarlas {
             var pSize = pEnd - pStart;
             Runnable r = () -> {
                 try {
-                    var buffer = channel.map(FileChannel.MapMode.READ_ONLY, pStart, pSize).order(ByteOrder.LITTLE_ENDIAN);
+                    var ms = channel.map(FileChannel.MapMode.READ_ONLY, pStart, pSize, ARENA);
-                    partitions[pIdx] = processBuffer(buffer, pIdx == 0);
+                    partitions[pIdx] = processSegment(ms, pIdx == 0, pIdx == numPartitions - 1);
                 }
                 catch (IOException e) {
                     throw new RuntimeException(e);
@@ -142,7 +146,7 @@ public class CalculateAverage_ebarlas {
             var merged = mergeFooterAndHeader(pPrev.footer, pNext.header);
             if (merged != null && merged.length != 0) {
                 if (merged[merged.length - 1] == '\n') { // fold into prev partition
-                    doProcessBuffer(ByteBuffer.wrap(merged).order(ByteOrder.LITTLE_ENDIAN), true, pPrev.stats);
+                    doProcessSegment(ARENA.allocateArray(ValueLayout.JAVA_BYTE, merged), 0, pPrev.stats, true);
                 }
                 else { // no newline appeared in partition, carry forward
                     pNext.footer = merged;
@@ -164,93 +168,121 @@ public class CalculateAverage_ebarlas {
         return merged;
     }
 
-    private static Partition processBuffer(ByteBuffer buffer, boolean first) {
+    private static Partition processSegment(MemorySegment ms, boolean first, boolean last) {
-        return doProcessBuffer(buffer, first, new Stats[HASH_TBL_SIZE + 1]);
+        var stats = new Stats[HASH_TBL_SIZE + 1]; // vals range from [0, size] inclusive
+        var header = first ? null : readHeader(ms);
+        var keyStart = doProcessSegment(ms, header == null ? 0 : header.offset, stats, last); // last segment is complete
+        var footer = keyStart < ms.byteSize() ? readFooter(ms, keyStart) : null;
+        return new Partition(header == null ? null : header.data, footer, stats);
     }
 
-    private static Partition doProcessBuffer(ByteBuffer buffer, boolean first, Stats[] stats) {
+    private static long doProcessSegment(MemorySegment ms, long offset, Stats[] stats, boolean complete) {
-        var header = first ? null : readHeader(buffer);
+        long cursor = ms.address() + offset;
-        var keyStart = reallyDoProcessBuffer(buffer, stats);
+        long keyBaseAddr = UNSAFE.allocateMemory(MAX_KEY_SIZE); // reusable target for current key data
-        var footer = keyStart < buffer.limit() ? readFooter(buffer, keyStart) : null;
+        long lineStart = cursor; // start of key in segment used for footer calc
-        return new Partition(header, footer, stats);
+        long limit = ms.address() + (complete ? ms.byteSize() : ms.byteSize() - MAX_LINE_SIZE); // stop short of longest line, sweep up at the end
-    }
+        while (cursor < limit) { // one line per iteration
-
+            lineStart = cursor; // preserve line start
-    private static int reallyDoProcessBuffer(ByteBuffer buffer, Stats[] stats) {
+            int keyHash = 0; // key hash code
-        long keyBaseAddr = UNSAFE.allocateMemory(MAX_KEY_SIZE);
+            long keyAddr = keyBaseAddr; // address for next int
-        int keyStart = 0; // start of key in buffer used for footer calc
+            int keyArrLen = 0; // number of key 4-byte ints
-        try { // abort with exception to allow optimistic line processing
+            int keyLastBytes; // occupancy in last byte (1, 2, 3, or 4)
-            while (true) { // one line per iteration
+            byte b0, b1, b2, b3;
-                keyStart = buffer.position(); // preserve line start
+            while (true) {
-                int keyHash = 0; // key hash code
+                int n = UNSAFE.getInt(cursor);
-                long keyAddr = keyBaseAddr; // address for next int
+                cursor += 4;
-                int keyArrLen = 0; // number of key 4-byte ints
+                b0 = (byte) (n & 0xFF);
-                int keyLastBytes; // occupancy in last byte (1, 2, 3, or 4)
+                b1 = (byte) ((n >> 8) & 0xFF);
-                int val; // temperature value
+                b2 = (byte) ((n >> 16) & 0xFF);
-                while (true) {
+                b3 = (byte) ((n >> 24) & 0xFF);
-                    int n = buffer.getInt();
+                if (b0 == ';') { // ...;1.1
-                    byte b0 = (byte) (n & 0xFF);
+                    keyLastBytes = 4;
-                    byte b1 = (byte) ((n >> 8) & 0xFF);
+                    b0 = b1;
-                    byte b2 = (byte) ((n >> 16) & 0xFF);
+                    b1 = b2;
-                    byte b3 = (byte) ((n >> 24) & 0xFF);
+                    b2 = b3;
-                    if (b0 == ';') { // ...;1.1
+                    b3 = (byte) (UNSAFE.getByte(cursor++) & 0xFF);
-                        val = getVal(buffer, b1, b2, b3, buffer.get());
+                    break;
-                        keyLastBytes = 4;
-                        break;
-                    }
-                    else if (b1 == ';') { // ...a;1.1
-                        val = getVal(buffer, b2, b3, buffer.get(), buffer.get());
-                        UNSAFE.putInt(keyAddr, b0);
-                        keyLastBytes = 1;
-                        keyArrLen++;
-                        keyHash = HASH_FACTOR * keyHash + b0;
-                        break;
-                    }
-                    else if (b2 == ';') { // ...ab;1.1
-                        val = getVal(buffer, b3, buffer.get(), buffer.get(), buffer.get());
-                        UNSAFE.putInt(keyAddr, n & 0x0000FFFF);
-                        keyLastBytes = 2;
-                        keyArrLen++;
-                        keyHash = HASH_FACTOR * (HASH_FACTOR * keyHash + b0) + b1;
-                        break;
-                    }
-                    else if (b3 == ';') { // ...abc;1.1
-                        UNSAFE.putInt(keyAddr, n & 0x00FFFFFF);
-                        keyLastBytes = 3;
-                        keyArrLen++;
-                        keyHash = HASH_FACTOR * (HASH_FACTOR * (HASH_FACTOR * keyHash + b0) + b1) + b2;
-                        n = buffer.getInt();
-                        b0 = (byte) (n & 0xFF);
-                        b1 = (byte) ((n >> 8) & 0xFF);
-                        b2 = (byte) ((n >> 16) & 0xFF);
-                        b3 = (byte) ((n >> 24) & 0xFF);
-                        val = getVal(buffer, b0, b1, b2, b3);
-                        break;
-                    }
-                    else {
-                        UNSAFE.putInt(keyAddr, n);
-                        keyArrLen++;
-                        keyAddr += 4;
-                        keyHash = HASH_FACTOR * (HASH_FACTOR * (HASH_FACTOR * (HASH_FACTOR * keyHash + b0) + b1) + b2) + b3;
-                    }
                 }
-                var idx = keyHash & HASH_TBL_SIZE;
+                else if (b1 == ';') { // ...a;1.1
-                var st = stats[idx];
+                    int k = n & 0xFF;
-                if (st == null) { // nothing in table, eagerly claim spot
+                    UNSAFE.putInt(keyAddr, k);
-                    st = stats[idx] = newStats(keyBaseAddr, keyArrLen, keyLastBytes, keyHash);
+                    keyLastBytes = 1;
+                    keyArrLen++;
+                    keyHash = HASH_FACTOR * keyHash + b0;
+                    b0 = b2;
+                    b1 = b3;
+                    b2 = (byte) (UNSAFE.getByte(cursor++) & 0xFF);
+                    b3 = (byte) (UNSAFE.getByte(cursor++) & 0xFF);
+                    break;
                 }
-                else if (!equals(st.keyAddr, st.keyLen, keyBaseAddr, keyArrLen)) {
+                else if (b2 == ';') { // ...ab;1.1
-                    st = findInTable(stats, keyHash, keyBaseAddr, keyArrLen, keyLastBytes);
+                    int k = n & 0xFFFF;
+                    UNSAFE.putInt(keyAddr, k);
+                    keyLastBytes = 2;
+                    keyArrLen++;
+                    keyHash = HASH_FACTOR * (HASH_FACTOR * keyHash + b0) + b1;
+                    b0 = b3;
+                    b1 = (byte) (UNSAFE.getByte(cursor++) & 0xFF);
+                    b2 = (byte) (UNSAFE.getByte(cursor++) & 0xFF);
+                    b3 = (byte) (UNSAFE.getByte(cursor++) & 0xFF);
+                    break;
+                }
+                else if (b3 == ';') { // ...abc;1.1
+                    int k = n & 0xFFFFFF;
+                    UNSAFE.putInt(keyAddr, k);
+                    keyLastBytes = 3;
+                    keyArrLen++;
+                    keyHash = HASH_FACTOR * (HASH_FACTOR * (HASH_FACTOR * keyHash + b0) + b1) + b2;
+                    n = UNSAFE.getInt(cursor);
+                    cursor += 4;
+                    b0 = (byte) (n & 0xFF);
+                    b1 = (byte) ((n >> 8) & 0xFF);
+                    b2 = (byte) ((n >> 16) & 0xFF);
+                    b3 = (byte) ((n >> 24) & 0xFF);
+                    break;
+                }
+                else {
+                    UNSAFE.putInt(keyAddr, n);
+                    keyArrLen++;
+                    keyAddr += 4;
+                    keyHash = HASH_FACTOR * (HASH_FACTOR * (HASH_FACTOR * (HASH_FACTOR * keyHash + b0) + b1) + b2) + b3;
                 }
-                st.min = Math.min(st.min, val);
-                st.max = Math.max(st.max, val);
-                st.sum += val;
-                st.count++;
             }
+            var idx = keyHash & HASH_TBL_SIZE;
+            var st = stats[idx];
+            if (st == null) { // nothing in table, eagerly claim spot
+                st = stats[idx] = newStats(keyBaseAddr, keyArrLen, keyLastBytes, keyHash);
+            }
+            else if (!equals(st.keyAddr, st.keyLen, keyBaseAddr, keyArrLen)) {
+                st = findInTable(stats, keyHash, keyBaseAddr, keyArrLen, keyLastBytes);
+            }
+            int val;
+            if (b0 == '-') {
+                if (b2 != '.') { // 6 bytes: -dd.dn
+                    var b = UNSAFE.getByte(cursor);
+                    cursor += 2; // adv beyond digit and newline
+                    val = -(((b1 - '0') * 10 + (b2 - '0')) * 10 + (b - '0'));
+                }
+                else { // 5 bytes: -d.dn
+                    cursor++; // newline
+                    val = -((b1 - '0') * 10 + (b3 - '0'));
+                }
+            }
+            else {
+                if (b1 != '.') { // 5 bytes: dd.dn
+                    cursor++; // newline
+                    val = ((b0 - '0') * 10 + (b1 - '0')) * 10 + (b3 - '0');
+                }
+                else { // 4 bytes: d.dn
+                    val = (b0 - '0') * 10 + (b2 - '0');
+                }
+            }
+            st.min = Math.min(st.min, val);
+            st.max = Math.max(st.max, val);
+            st.sum += val;
+            st.count++;
         }
-        catch (BufferUnderflowException ignore) {
+        return lineStart - ms.address();
-
-        }
-        return keyStart;
     }
 
     private static boolean equals(long key1, int len1, long key2, int len2) {
@@ -261,7 +293,7 @@ public class CalculateAverage_ebarlas {
             return UNSAFE.getLong(key1) == UNSAFE.getLong(key2);
         }
         if (len1 == 3) {
-            return UNSAFE.getInt(key1) == UNSAFE.getInt(key2) && UNSAFE.getInt(key1 + 4) == UNSAFE.getInt(key2 + 4);
+            return UNSAFE.getLong(key1) == UNSAFE.getLong(key2) && UNSAFE.getInt(key1 + 8) == UNSAFE.getInt(key2 + 8);
         }
         if (len1 == 1) {
             return UNSAFE.getInt(key1) == UNSAFE.getInt(key2);
@@ -278,29 +310,6 @@ public class CalculateAverage_ebarlas {
         return true;
     }
 
-    private static int getVal(ByteBuffer buffer, byte b0, byte b1, byte b2, byte b3) {
-        if (b0 == '-') {
-            if (b2 != '.') { // 6 bytes: -dd.dn
-                var b = buffer.get();
-                buffer.get(); // newline
-                return -(((b1 - '0') * 10 + (b2 - '0')) * 10 + (b - '0'));
-            }
-            else { // 5 bytes: -d.dn
-                buffer.get(); // newline
-                return -((b1 - '0') * 10 + (b3 - '0'));
-            }
-        }
-        else {
-            if (b1 != '.') { // 5 bytes: dd.dn
-                buffer.get(); // newline
-                return ((b0 - '0') * 10 + (b1 - '0')) * 10 + (b3 - '0');
-            }
-            else { // 4 bytes: d.dn
-                return (b0 - '0') * 10 + (b2 - '0');
-            }
-        }
-    }
-
     private static Stats findInTable(Stats[] stats, int hash, long keyAddr, int keyLen, int keyLastBytes) { // open-addressing scan
         var idx = hash & HASH_TBL_SIZE;
         var st = stats[idx];
@@ -321,18 +330,26 @@ public class CalculateAverage_ebarlas {
         return new Stats(k, keyLen, keyLastBytes, hash);
     }
 
-    private static byte[] readFooter(ByteBuffer buffer, int lineStart) { // read from line start to current pos (end-of-input)
+    private static byte[] readFooter(MemorySegment ms, long offset) { // read from line start to current pos (end-of-input)
-        var footer = new byte[buffer.limit() - lineStart];
+        var footer = new byte[(int) (ms.byteSize() - offset)];
-        buffer.get(lineStart, footer, 0, footer.length);
+        for (int i = 0; i < footer.length; i++) {
+            footer[i] = ms.get(ValueLayout.JAVA_BYTE, offset + i);
+        }
         return footer;
     }
 
-    private static byte[] readHeader(ByteBuffer buffer) { // read up to and including first newline (or end-of-input)
+    private static ByteArrayOffset readHeader(MemorySegment ms) { // read up to and including first newline (or end-of-input)
-        while (buffer.hasRemaining() && buffer.get() != '\n')
+        long offset = 0;
+        while (offset < ms.byteSize() && ms.get(ValueLayout.JAVA_BYTE, offset++) != '\n')
             ;
-        var header = new byte[buffer.position()];
+        var header = new byte[(int) offset];
-        buffer.get(0, header, 0, header.length);
+        for (int i = 0; i < offset; i++) {
-        return header;
+            header[i] = ms.get(ValueLayout.JAVA_BYTE, i);
+        }
+        return new ByteArrayOffset(header, offset);
+    }
+
+    record ByteArrayOffset(byte[] data, long offset) {
     }
 
     private static class Partition {