Add function to get valid entries only from table

contrib/long_distance_matching/Makefile

@@ -25,17 +25,17 @@ LDFLAGS += -lzstd
 
 default: all
 
-all: main-basic main-chaining
+all: main-basic main-circular-buffer
 
 main-basic : basic_table.c ldm.c main-ldm.c
 	$(CC) $(CPPFLAGS) $(CFLAGS) $^ $(LDFLAGS) -o $@
 
-main-chaining : chaining_table.c ldm.c main-ldm.c
+main-circular-buffer: circular_buffer_table.c ldm.c main-ldm.c
 	$(CC) $(CPPFLAGS) $(CFLAGS) $^ $(LDFLAGS) -o $@
 
 
 clean:
 	@rm -f core *.o tmp* result* *.ldm *.ldm.dec \
-	main-basic main-chaining
+	main-basic main-circular-buffer
 	@echo Cleaning completed
 

contrib/long_distance_matching/basic_table.c

@@ -27,12 +27,29 @@ LDM_hashEntry *getBucket(const LDM_hashTable *table, const hash_t hash) {
   return table->entries + hash;
 }
 
+
 LDM_hashEntry *HASH_getEntryFromHash(
     const LDM_hashTable *table, const hash_t hash, const U32 checksum) {
   (void)checksum;
   return getBucket(table, hash);
 }
 
+LDM_hashEntry *HASH_getValidEntry(const LDM_hashTable *table,
+                                  const hash_t hash,
+                                  const U32 checksum,
+                                  const BYTE *pIn,
+                                  int (*isValid)(const BYTE *pIn, const BYTE *pMatch)) {
+  LDM_hashEntry *entry = getBucket(table, hash);
+  (void)checksum;
+  if ((*isValid)(pIn, entry->offset + table->offsetBase)) {
+    return entry;
+  } else {
+    return NULL;
+  }
+}
+
+
+
 void HASH_insert(LDM_hashTable *table,
                  const hash_t hash, const LDM_hashEntry entry) {
   *getBucket(table, hash) = entry;

contrib/long_distance_matching/circular_buffer_table.c

@@ -9,7 +9,7 @@
 //      refactor code to scale the number of elements appropriately.
 
 // Number of elements per hash bucket.
-#define HASH_BUCKET_SIZE_LOG 2  // MAX is 4 for now
+#define HASH_BUCKET_SIZE_LOG 1  // MAX is 4 for now
 #define HASH_BUCKET_SIZE (1 << (HASH_BUCKET_SIZE_LOG))
 
 struct LDM_hashTable {
@@ -44,6 +44,25 @@ static LDM_hashEntry *getLastInsertFromHash(const LDM_hashTable *table,
 }
 */
 
+LDM_hashEntry *HASH_getValidEntry(const LDM_hashTable *table,
+                                  const hash_t hash,
+                                  const U32 checksum,
+                                  const BYTE *pIn,
+                                  int (*isValid)(const BYTE *pIn, const BYTE *pMatch)) {
+  LDM_hashEntry *bucket = getBucket(table, hash);
+  LDM_hashEntry *cur = bucket;
+  // TODO: in order of recency?
+  for (; cur < bucket + HASH_BUCKET_SIZE; ++cur) {
+    // CHeck checksum for faster check.
+    if (cur->checksum == checksum &&
+        (*isValid)(pIn, cur->offset + table->offsetBase)) {
+      return cur;
+    }
+  }
+  return NULL;
+}
+
+
 LDM_hashEntry *HASH_getEntryFromHash(const LDM_hashTable *table,
                                      const hash_t hash,
                                      const U32 checksum) {

contrib/long_distance_matching/ldm.c

@@ -5,7 +5,7 @@
 #include <string.h>
 
 // Insert every (HASH_ONLY_EVERY + 1) into the hash table.
-#define HASH_ONLY_EVERY 0
+#define HASH_ONLY_EVERY 31
 
 #define LDM_HASHLOG (LDM_MEMORY_USAGE-2)
 #define LDM_HASHTABLESIZE (1 << (LDM_MEMORY_USAGE))
@@ -38,8 +38,6 @@ struct LDM_compressStats {
   U32 numCollisions;
   U32 numHashInserts;
 
-//  U64 numInvalidHashes, numValidHashes; // tmp
-
   U32 offsetHistogram[32];
 };
 
@@ -153,45 +151,25 @@ void LDM_printCompressStats(const LDM_compressStats *stats) {
                    (double) stats->numMatches);
   }
   printf("\n");
-
-  /*
-  printf("Num invalid hashes, num valid hashes, %llu %llu\n",
-         stats->numInvalidHashes, stats->numValidHashes);
-  */
-  /*
-  printf("num collisions, num hash inserts, %% collisions: %u, %u, %.3f\n",
-         stats->numCollisions, stats->numHashInserts,
-         stats->numHashInserts == 0 ?
-            1.0 : (100.0 * (double)stats->numCollisions) /
-                  (double)stats->numHashInserts);
-  */
   printf("=====================\n");
 
 }
 
 int LDM_isValidMatch(const BYTE *pIn, const BYTE *pMatch) {
-  /*
-  if (memcmp(pIn, pMatch, LDM_MIN_MATCH_LENGTH) == 0) {
-    return 1;
-  }
-  return 0;
-  */
-
-  //TODO: This seems to be faster for some reason?
-
   U32 lengthLeft = LDM_MIN_MATCH_LENGTH;
   const BYTE *curIn = pIn;
   const BYTE *curMatch = pMatch;
 
-  for (; lengthLeft >= 8; lengthLeft -= 8) {
-    if (MEM_read64(curIn) != MEM_read64(curMatch)) {
+  if (pIn - pMatch > LDM_WINDOW_SIZE) {
     return 0;
   }
-    curIn += 8;
-    curMatch += 8;
+
+  for (; lengthLeft >= 4; lengthLeft -= 4) {
+    if (MEM_read32(curIn) != MEM_read32(curMatch)) {
+      return 0;
     }
-  if (lengthLeft > 0) {
-    return (MEM_read32(curIn) == MEM_read32(curMatch));
+    curIn += 4;
+    curMatch += 4;
   }
   return 1;
 }
@@ -307,8 +285,11 @@ static void putHashOfCurrentPositionFromHash(
   // Hash only every HASH_ONLY_EVERY times, based on cctx->ip.
   // Note: this works only when cctx->step is 1.
   if (((cctx->ip - cctx->ibase) & HASH_ONLY_EVERY) == HASH_ONLY_EVERY) {
+    /**
     const LDM_hashEntry entry = { cctx->ip - cctx->ibase ,
                                   MEM_read32(cctx->ip) };
+                                  */
+    const LDM_hashEntry entry = { cctx->ip - cctx->ibase, sum };
     HASH_insert(cctx->hashTable, hash, entry);
   }
 
@@ -438,7 +419,7 @@ static int LDM_findBestMatch(LDM_CCtx *cctx, const BYTE **match) {
   LDM_hashEntry *entry = NULL;
   cctx->nextIp = cctx->ip + cctx->step;
 
-  do {
+  while (entry == NULL) {
     hash_t h;
     U32 sum;
     setNextHash(cctx);
@@ -451,17 +432,14 @@ static int LDM_findBestMatch(LDM_CCtx *cctx, const BYTE **match) {
       return 1;
     }
 
-    entry = HASH_getEntryFromHash(cctx->hashTable, h, MEM_read32(cctx->ip));
+    entry = HASH_getValidEntry(cctx->hashTable, h, sum, cctx->ip,
+                               &LDM_isValidMatch);
 
     if (entry != NULL) {
       *match = entry->offset + cctx->ibase;
     }
-
     putHashOfCurrentPositionFromHash(cctx, h, sum);
-
-  } while (entry == NULL ||
-           (cctx->ip - *match > LDM_WINDOW_SIZE ||
-           !LDM_isValidMatch(cctx->ip, *match)));
+  }
   setNextHash(cctx);
   return 0;
 }

contrib/long_distance_matching/ldm.h

@@ -11,14 +11,14 @@
 #define LDM_OFFSET_SIZE 4
 
 // Defines the size of the hash table.
-#define LDM_MEMORY_USAGE 16
+#define LDM_MEMORY_USAGE 20
 
-#define LDM_WINDOW_SIZE_LOG 25
+#define LDM_WINDOW_SIZE_LOG 30
 #define LDM_WINDOW_SIZE (1 << (LDM_WINDOW_SIZE_LOG))
 
 //These should be multiples of four.
-#define LDM_MIN_MATCH_LENGTH 1024
-#define LDM_HASH_LENGTH 1024
+#define LDM_MIN_MATCH_LENGTH 64
+#define LDM_HASH_LENGTH 64
 
 typedef struct LDM_compressStats LDM_compressStats;
 typedef struct LDM_CCtx LDM_CCtx;
@@ -82,7 +82,8 @@ void LDM_outputHashTableOffsetHistogram(const LDM_CCtx *cctx);
 void LDM_printCompressStats(const LDM_compressStats *stats);
 /**
  * Checks whether the LDM_MIN_MATCH_LENGTH bytes from p are the same as the
- * LDM_MIN_MATCH_LENGTH bytes from match.
+ * LDM_MIN_MATCH_LENGTH bytes from match and also if
+ * pIn - pMatch <= LDM_WINDOW_SIZE.
  *
  * This assumes LDM_MIN_MATCH_LENGTH is a multiple of four.
  *

contrib/long_distance_matching/ldm_hashtable.h

@@ -7,7 +7,7 @@ typedef U32 hash_t;
 
 typedef struct LDM_hashEntry {
   U32 offset;
-  U32 checksum; // Not needed?
+  U32 checksum;
 } LDM_hashEntry;
 
 typedef struct LDM_hashTable LDM_hashTable;
@@ -17,10 +17,17 @@ typedef struct LDM_hashTable LDM_hashTable;
 
 LDM_hashTable *HASH_createTable(U32 size, const BYTE *offsetBase);
 
+//TODO: unneeded?
 LDM_hashEntry *HASH_getEntryFromHash(const LDM_hashTable *table,
                                      const hash_t hash,
                                      const U32 checksum);
 
+LDM_hashEntry *HASH_getValidEntry(const LDM_hashTable *table,
+                                  const hash_t hash,
+                                  const U32 checksum,
+                                  const BYTE *pIn,
+                                  int (*isValid)(const BYTE *pIn, const BYTE *pMatch));
+
 void HASH_insert(LDM_hashTable *table, const hash_t hash,
                         const LDM_hashEntry entry);