slightly improved weight calculation

translating into a tiny compression ratio improvement

lib/compress/zstd_compress.c

@@ -1977,7 +1977,7 @@ static void ZSTD_storeLastLiterals(seqStore_t* seqStorePtr,
     seqStorePtr->lit += lastLLSize;
 }
 
-static void ZSTD_resetSeqStore(seqStore_t* ssPtr)
+void ZSTD_resetSeqStore(seqStore_t* ssPtr)
 {
     ssPtr->lit = ssPtr->litStart;
     ssPtr->sequences = ssPtr->sequencesStart;

lib/compress/zstd_compress_internal.h

@@ -658,6 +658,8 @@ size_t ZSTD_initCStream_internal(ZSTD_CStream* zcs,
                      const ZSTD_CDict* cdict,
                      ZSTD_CCtx_params  params, unsigned long long pledgedSrcSize);
 
+void ZSTD_resetSeqStore(seqStore_t* ssPtr);
+
 /*! ZSTD_compressStream_generic() :
  *  Private use only. To be called from zstdmt_compress.c in single-thread mode. */
 size_t ZSTD_compressStream_generic(ZSTD_CStream* zcs,

lib/compress/zstd_opt.c

@@ -25,29 +25,29 @@
 #  define BITCOST_ACCURACY 0
 #  define BITCOST_MULTIPLIER (1 << BITCOST_ACCURACY)
 #  define WEIGHT(stat)  ((void)opt, ZSTD_bitWeight(stat))
-#elif 0  /* fractional bit accuracy */
+#elif 1  /* fractional bit accuracy */
 #  define BITCOST_ACCURACY 8
 #  define BITCOST_MULTIPLIER (1 << BITCOST_ACCURACY)
 #  define WEIGHT(stat,opt) ((void)opt, ZSTD_fracWeight(stat))
 #else    /* opt==approx, ultra==accurate */
 #  define BITCOST_ACCURACY 8
 #  define BITCOST_MULTIPLIER (1 << BITCOST_ACCURACY)
-#  define WEIGHT(stat,opt) (opt ? ZSTD_fracWeight(stat) : ZSTD_bitWeight(stat) )
+#  define WEIGHT(stat,opt) (opt ? ZSTD_fracWeight(stat) : ZSTD_bitWeight(stat))
 #endif
 
 MEM_STATIC U32 ZSTD_bitWeight(U32 stat)
 {
-    return (ZSTD_highbit32((stat)+1) * BITCOST_MULTIPLIER);
+    return (ZSTD_highbit32(stat+1) * BITCOST_MULTIPLIER);
 }
 
-MEM_STATIC U32 ZSTD_fracWeight(U32 stat)
+MEM_STATIC U32 ZSTD_fracWeight(U32 rawStat)
 {
-    U32 const hb = stat ? ZSTD_highbit32(stat) : 0;
+    U32 const stat = rawStat + 1;
+    U32 const hb = ZSTD_highbit32(stat);
     U32 const BWeight = hb * BITCOST_MULTIPLIER;
     U32 const FWeight = (stat << BITCOST_ACCURACY) >> hb;
     U32 const weight = BWeight + FWeight;
     assert(hb + BITCOST_ACCURACY < 31);
-    DEBUGLOG(2, "stat=%u, hb=%u, weight=%u", stat, hb, weight)
     return weight;
 }