Added SWAR (SIMD Within A Register) code to increase bytebuffer proce…

…ssing/throughput

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

@@ -125,6 +125,9 @@ public void run() throws Exception {
         }
     }
 
+    private static final long SEPARATOR_PATTERN = compilePattern((byte) ';');
+    private static final long EOL_PATTERN = compilePattern((byte) '\n');
+
     private BitTwiddledMap processBuffer(ByteBuffer bb) {
 
         BitTwiddledMap measurements = new BitTwiddledMap();
@@ -134,49 +137,68 @@ private BitTwiddledMap processBuffer(ByteBuffer bb) {
 
         while (bb.position() < limit) {
 
-            // Find the correct positions in the bytebuffer:
-
-            // Start:
             final int startPointer = bb.position();
 
-            // Separator:
-            int separatorPointer = startPointer + 3; // key is at least 3 long
-            while (separatorPointer != limit && bb.get(separatorPointer) != ';') {
-                separatorPointer++;
-            }
+            int separatorPointer = findNextSWAR(bb, SEPARATOR_PATTERN, startPointer + 3, limit);
+            int endPointer = findNextSWAR(bb, EOL_PATTERN, separatorPointer + 3, limit);
 
-            // EOL:
-            int endPointer = separatorPointer + 3; // temperature is at least 3 long
-            while (endPointer != limit && bb.get(endPointer) != '\n')
-                endPointer++;
+            final int entryLength = endPointer - startPointer;
 
-            // Extract the name of the key and move the bytebuffer:
+            // Read the entry in a single get():
+            bb.get(buffer, 0, entryLength);
+            bb.position(endPointer + 1); // skip the separator
+
+            // Extract the name of the key:
             final int nameLength = separatorPointer - startPointer;
-            bb.get(buffer, 0, nameLength);
             final String key = new String(buffer, 0, nameLength);
 
-            bb.get(); // skip the separator
-
             // Extract the measurement value (10x), skip making a String altogether:
             final int valueLength = endPointer - separatorPointer - 1;
-            bb.get(buffer, 0, valueLength);
+            final int measured = branchlessParseInt(buffer, nameLength + 1, valueLength);
 
-            // and get rid of the new line (handle both kinds)
-            byte newline = bb.get();
-            if (newline == '\r')
-                bb.get();
-
-            int measured = branchlessParseInt(buffer, valueLength);
-
-            // Update the map, computeIfAbsent has the least amount of branches I think, compared to get()/put() or merge() or compute():
             measurements.getOrCreate(key).updateWith(measured);
         }
 
         return measurements;
     }
 
     /**
-     * Thanks to bjhara for the idea of using memory mapped files, TIL.
+     * -------- This section contains SWAR code (SIMD Within A Register) which processes a bytebuffer as longs to find values:
+     */
+
+    private int findNextSWAR(ByteBuffer bb, long pattern, int start, int limit) {
+        int i;
+        for (i = start; i <= limit - 8; i += 8) {
+            long word = bb.getLong(i);
+            int index = firstAnyPattern(word, pattern);
+            if (index < Long.BYTES) {
+                return i + index;
+            }
+        }
+        // Handle remaining bytes
+        for (; i < limit; i++) {
+            if (bb.get(i) == (byte) pattern) {
+                return i;
+            }
+        }
+        return limit; // delimiter not found
+    }
+
+    private static long compilePattern(byte value) {
+        return ((long) value << 56) | ((long) value << 48) | ((long) value << 40) | ((long) value << 32) |
+                ((long) value << 24) | ((long) value << 16) | ((long) value << 8) | (long) value;
+    }
+
+    private static int firstAnyPattern(long word, long pattern) {
+        final long match = word ^ pattern;
+        long mask = match - 0x0101010101010101L;
+        mask &= ~match;
+        mask &= 0x8080808080808080L;
+        return Long.numberOfLeadingZeros(mask) >> 3;
+    }
+
+    /**
+     * -------- Thanks to bjhara for the idea of using memory mapped files.
      * @param fileChannel
      * @return
      * @throws IOException
@@ -224,15 +246,15 @@ public boolean hasNext() {
      * @param input
      * @return int value x10
      */
-    private static int branchlessParseInt(final byte[] input, int length) {
+    private static int branchlessParseInt(final byte[] input, int start, int length) {
         // 0 if positive, 1 if negative
-        final int negative = ~(input[0] >> 4) & 1;
+        final int negative = ~(input[start] >> 4) & 1;
         // 0 if nr length is 3, 1 if length is 4
         final int has4 = ((length - negative) >> 2) & 1;
 
-        final int digit1 = input[negative] - '0';
-        final int digit2 = input[negative + has4] - '0';
-        final int digit3 = input[2 + negative + has4] - '0';
+        final int digit1 = input[start + negative] - '0';
+        final int digit2 = input[start + negative + has4] - '0';
+        final int digit3 = input[start + 2 + negative + has4] - '0';
 
         return (-negative ^ (has4 * (digit1 * 100) + digit2 * 10 + digit3) - negative);
     }