Introducing the vector api. 1s faster on 4 core i7 (#506)

Co-authored-by: Ian Preston <ianopolous@protonmail.com>

calculate_average_ianopolousfast.sh

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

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

@@ -15,6 +15,10 @@
  */
 package dev.morling.onebrc;
 
+import jdk.incubator.vector.ByteVector;
+import jdk.incubator.vector.VectorOperators;
+import jdk.incubator.vector.VectorSpecies;
+
 import java.lang.foreign.Arena;
 import java.lang.foreign.MemorySegment;
 import java.nio.ByteOrder;
@@ -30,19 +34,23 @@ import static java.lang.foreign.ValueLayout.*;
 /* A fast implementation with no unsafe.
  * Features:
  * * memory mapped file using preview Arena FFI
+ * * semicolon finding using incubator vector api
  * * read chunks in parallel
  * * minimise allocation
  * * no unsafe
  *
  * Timings on 4 core i7-7500U CPU @ 2.70GHz:
  * average_baseline: 4m48s
- * ianopolous:         16s
+ * ianopolous:         15s
 */
 public class CalculateAverage_ianopolousfast {
 
     public static final int MAX_LINE_LENGTH = 107;
     public static final int MAX_STATIONS = 1 << 14;
     private static final OfLong LONG_LAYOUT = JAVA_LONG_UNALIGNED.withOrder(ByteOrder.BIG_ENDIAN);
+    private static final VectorSpecies<Byte> BYTE_SPECIES = ByteVector.SPECIES_PREFERRED.length() >= 32
+            ? ByteVector.SPECIES_256
+            : ByteVector.SPECIES_128;
 
     public static void main(String[] args) throws Exception {
         Arena arena = Arena.global();
@@ -165,58 +173,40 @@ public class CalculateAverage_ianopolousfast {
         }
     }
 
-    public static long hasSemicolon(long d) {
-        // from Hacker's Delight page 92
-        d = d ^ 0x3b3b3b3b3b3b3b3bL;
-        long y = (d & 0x7f7f7f7f7f7f7f7fL) + 0x7f7f7f7f7f7f7f7fL;
-        return ~(y | d | 0x7f7f7f7f7f7f7f7fL);
-    }
-
-    public static int getSemicolonIndex(long y) {
-        // from Hacker's Delight page 92
-        return Long.numberOfLeadingZeros(y) >> 3;
-    }
-
     static long maskHighBytes(long d, int nbytes) {
         return d & (-1L << ((8 - nbytes) * 8));
     }
 
     public static Stat parseStation(long lineStart, MemorySegment buffer, List<List<Stat>> stations) {
-        // find semicolon and update hash as we go, reading a long at a time
+        ByteVector line = ByteVector.fromMemorySegment(BYTE_SPECIES, buffer, lineStart, ByteOrder.nativeOrder());
-        long d = buffer.get(LONG_LAYOUT, lineStart);
+        int keySize = line.compare(VectorOperators.EQ, ';').firstTrue();
-        long hasSemi = hasSemicolon(d);
-        if (hasSemi != 0) {
-            int semiIndex = getSemicolonIndex(hasSemi);
-            d = maskHighBytes(d, semiIndex);
-            return dedupeStation8(lineStart, lineStart + semiIndex, d, d, buffer, stations);
-        }
-        long first8 = d;
-        long hash = d;
 
-        d = buffer.get(LONG_LAYOUT, lineStart + 8);
+        if (keySize == BYTE_SPECIES.vectorByteSize()) {
-        hasSemi = hasSemicolon(d);
+            while (buffer.get(JAVA_BYTE, lineStart + keySize) != ';') {
-        if (hasSemi != 0) {
+                keySize++;
-            int semiIndex = getSemicolonIndex(hasSemi);
+            }
-            if (semiIndex == 0)
+            long first8 = buffer.get(LONG_LAYOUT, lineStart);
-                return dedupeStation8(lineStart, lineStart + 8, first8, first8, buffer, stations);
+            if (keySize < 8)
-            d = maskHighBytes(d, semiIndex);
+                return dedupeStation8(lineStart, lineStart + keySize, first8, first8, buffer, stations);
-            return dedupeStation16(lineStart, lineStart + 8 + semiIndex, first8 ^ d, first8, d, buffer, stations);
+            long second8 = buffer.get(LONG_LAYOUT, lineStart + 8);
+            if (keySize < 16)
+                return dedupeStation16(lineStart, lineStart + keySize, first8 ^ second8, first8, second8, buffer, stations);
+            long hash = first8 ^ second8; // todo include other bytes
+            return dedupeStation(lineStart, lineStart + keySize, hash, first8, second8, buffer, stations);
         }
 
-        int index = 8;
+        long first8 = buffer.get(LONG_LAYOUT, lineStart);
-        long second8 = d;
+        if (keySize <= 8) {
-        while (hasSemi == 0) {
+            first8 = maskHighBytes(first8, keySize & 0x07);
-            hash = hash ^ d;
+            return dedupeStation8(lineStart, lineStart + keySize, first8, first8, buffer, stations);
-            index += 8;
-            d = buffer.get(LONG_LAYOUT, lineStart + index);
-            hasSemi = hasSemicolon(d);
         }
-        int semiIndex = getSemicolonIndex(hasSemi);
+        long second8 = buffer.get(LONG_LAYOUT, lineStart + 8);
-        d = maskHighBytes(d, semiIndex);
+        if (keySize < 16) {
-        if (semiIndex > 0) {
+            second8 = maskHighBytes(second8, keySize & 0x07);
-            hash = hash ^ d;
+            return dedupeStation16(lineStart, lineStart + keySize, first8 ^ second8, first8, second8, buffer, stations);
         }
-        return dedupeStation(lineStart, lineStart + index + semiIndex, hash, first8, second8, buffer, stations);
+        long hash = first8 ^ second8; // todo include later bytes
+        return dedupeStation(lineStart, lineStart + keySize, hash, first8, second8, buffer, stations);
     }
 
     public static int getDot(long d) {
@@ -266,24 +256,30 @@ public class CalculateAverage_ianopolousfast {
         for (int i = 0; i < MAX_STATIONS; i++)
             stations.add(null);
 
-        // Handle reading the very last line in the file
+        // Handle reading the very last few lines in the file
-        // this allows us to not worry about reading a long beyond the end
+        // this allows us to not worry about reading beyond the end
         // in the inner loop (reducing branches)
-        // We only need to read one because the min record size is 6 bytes
+        // We need at least the vector lane size bytes back
-        // so 2nd last record must be > 8 from end
         if (endByte == buffer.byteSize()) {
-            endByte -= 2; // skip final new line
+            endByte -= 1; // skip final new line
-            while (endByte > 0 && buffer.get(JAVA_BYTE, endByte) != '\n')
+            // reverse at least vector lane width
+            while (endByte > 0 && buffer.byteSize() - endByte < BYTE_SPECIES.vectorByteSize()) {
                 endByte--;
+                while (endByte > 0 && buffer.get(JAVA_BYTE, endByte) != '\n')
+                    endByte--;
+            }
 
             if (endByte > 0)
                 endByte++;
-            // copy into a 8n sized buffer to avoid reading off end
+            // copy into a larger buffer to avoid reading off end
-            MemorySegment end = Arena.global().allocate(MAX_LINE_LENGTH + 4);
+            MemorySegment end = Arena.global().allocate(MAX_LINE_LENGTH + BYTE_SPECIES.vectorByteSize());
             for (long i = endByte; i < buffer.byteSize(); i++)
                 end.set(JAVA_BYTE, i - endByte, buffer.get(JAVA_BYTE, i));
-            Stat station = parseStation(0, end, stations);
+            int index = 0;
-            processTemperature(station.name.length + 1, end, station);
+            while (endByte + index < buffer.byteSize()) {
+                Stat station = parseStation(index, end, stations);
+                index = (int) processTemperature(index + station.name.length + 1, end, station);
+            }
         }
 
         while (startByte < endByte) {