From 1c1e6916e41c47ba06e848a51549f7911a6ad379 Mon Sep 17 00:00:00 2001
From: inikep <inikep@gmail.com>
Date: Fri, 18 Mar 2016 12:49:44 +0100
Subject: [PATCH] improved timer accuracy

---
 lib/zstd_decompress.c |  8 ++++++--
 lib/zstd_internal.h   |  2 +-
 programs/bench.c      | 20 ++++++++++++++++++--
 3 files changed, 25 insertions(+), 5 deletions(-)

diff --git a/lib/zstd_decompress.c b/lib/zstd_decompress.c
index bb7ad43d..d4974b30 100644
--- a/lib/zstd_decompress.c
+++ b/lib/zstd_decompress.c
@@ -687,12 +687,16 @@ static void ZSTD_decodeSequence(seq_t* seq, seqState_t* seqState, const U32 mls)
                 offset = 1-offset;
             if (offset != 0)
             {
+    #if 1
                 size_t temp = seqState->prevOffset[offset];
                 if (offset != 1) {
                     if (offset == 3) seqState->prevOffset[3] = seqState->prevOffset[2];
                     seqState->prevOffset[2] = seqState->prevOffset[1];
                 }
                 offset = temp;
+    #else
+                offset = seqState->prevOffset[1];
+    #endif
                 seqState->prevOffset[1] = seqState->prevOffset[0];
                 seqState->prevOffset[0] = offset;
             }
@@ -701,8 +705,8 @@ static void ZSTD_decodeSequence(seq_t* seq, seqState_t* seqState, const U32 mls)
         } else {
             offset -= ZSTD_REP_MOVE;
     #if 0
-            seqState->prevOffset[3] = seqState->prevOffset[2];
-            seqState->prevOffset[2] = seqState->prevOffset[1];
+        //    seqState->prevOffset[3] = seqState->prevOffset[2];
+        //    seqState->prevOffset[2] = seqState->prevOffset[1];
             seqState->prevOffset[1] = seqState->prevOffset[0];
             seqState->prevOffset[0] = offset;
     #else
diff --git a/lib/zstd_internal.h b/lib/zstd_internal.h
index dbce471a..669d4380 100644
--- a/lib/zstd_internal.h
+++ b/lib/zstd_internal.h
@@ -71,7 +71,7 @@
 #else
     #define ZSTD_REP_NUM    1
     #define ZSTD_REP_INIT   2
-    #define ZSTD_REP_MOVE  (ZSTD_REP_NUM-1)
+    #define ZSTD_REP_MOVE  0//(ZSTD_REP_NUM-1)
 #endif
 
 #define KB *(1 <<10)
diff --git a/programs/bench.c b/programs/bench.c
index ff01ca68..5808c2ec 100644
--- a/programs/bench.c
+++ b/programs/bench.c
@@ -44,13 +44,22 @@
 /* *************************************
 *  Includes
 ***************************************/
+#if defined(WIN32) || defined(_WIN32) || defined(__WIN32__) || defined(WIN64) || defined(_WIN64)
+	#define WINDOWS
+#endif
 #include <stdlib.h>      /* malloc, free */
 #include <string.h>      /* memset */
 #include <stdio.h>       /* fprintf, fopen, ftello64 */
 #include <sys/types.h>   /* stat64 */
 #include <sys/stat.h>    /* stat64 */
-#include <time.h>         /* clock_t, clock, CLOCKS_PER_SEC */
-
+#include <time.h>        /* clock_t, clock, CLOCKS_PER_SEC */
+#ifdef WINDOWS
+	#define mili_sleep(mili) Sleep(mili)
+#else
+	#define mili_sleep(mili) usleep(mili*1000)
+    #include <sys/resource.h> /* setpriority */
+#endif
+    
 /* sleep : posix - windows - others */
 #if !defined(_WIN32) && (defined(__unix__) || defined(__unix) || (defined(__APPLE__) && defined(__MACH__)))
 #  include <unistd.h>
@@ -283,6 +292,7 @@ static int BMK_benchMem(const void* srcBuffer, size_t srcSize,
             memset(compressedBuffer, 0xE5, maxCompressedSize);  /* warm up and erase result buffer */
 
             nbLoops = 0;
+            mili_sleep(1); // give processor to other processes
             clockStart = clock();
             while (clock() == clockStart);
             clockStart = clock();
@@ -313,6 +323,7 @@ static int BMK_benchMem(const void* srcBuffer, size_t srcSize,
             memset(resultBuffer, 0xD6, srcSize);  /* warm result buffer */
 
             nbLoops = 0;
+            mili_sleep(1); // give processor to other processes
             clockStart = clock();
             while (clock() == clockStart);
             clockStart = clock();
@@ -413,6 +424,11 @@ static void BMK_benchCLevel(void* srcBuffer, size_t benchedSize,
 {
     benchResult_t result, total;
     int l;
+#ifdef WINDOWS
+    SetPriorityClass(GetCurrentProcess(), REALTIME_PRIORITY_CLASS);
+#else
+    setpriority(PRIO_PROCESS, 0, -20);
+#endif
 
     const char* pch = strrchr(displayName, '\\'); /* Windows */
     if (!pch) pch = strrchr(displayName, '/'); /* Linux */