Add -nowrite arg to TJBench to improve consistency

Prevents any images from being written to disk, thus making the
performance of the benchmark as CPU-bound as possible.

ChangeLog.txt

@@ -52,6 +52,11 @@ Since the macro is used only internally, it has been moved into jconfigint.h.
 JSIMD_FORCENONE environment variable to 1 (the other SIMD implementations
 already had this capability.)
 
+[11] Added a new command-line argument to TJBench (-nowrite) that prevents the
+benchmark from outputting any images.  This removes any potential operating
+system overhead that might be caused by lazy writes to disk and thus improves
+the consistency of the performance measurements.
+
 
 1.4.2
 =====

java/TJBench.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (C)2009-2014 D. R. Commander.  All Rights Reserved.
+ * Copyright (C)2009-2014, 2016 D. R. Commander.  All Rights Reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
@@ -35,7 +35,7 @@ import org.libjpegturbo.turbojpeg.*;
 class TJBench {
 
   static int flags = 0, quiet = 0, pf = TJ.PF_BGR, yuvpad = 1, warmup = 1;
-  static boolean compOnly, decompOnly, doTile, doYUV;
+  static boolean compOnly, decompOnly, doTile, doYUV, write;
 
   static final String[] pixFormatStr = {
     "RGB", "BGR", "RGBX", "BGRX", "XBGR", "XRGB", "GRAY"
@@ -223,6 +223,8 @@ class TJBench {
       }
     }
 
+    if (!write) return;
+
     if (sf.getNum() != 1 || sf.getDenom() != 1)
       sizeStr = new String(sf.getNum() + "_" + sf.getDenom());
     else if (tilew != w || tileh != h)
@@ -394,7 +396,7 @@ class TJBench {
         System.out.format("                  Output bit stream:  %f Megabits/sec\n",
           (double)totalJpegSize * 8. / 1000000. * (double)iter / elapsed);
       }
-      if (tilew == w && tileh == h) {
+      if (tilew == w && tileh == h && write) {
         String tempStr = fileName + "_" + subName[subsamp] + "_" + "Q" +
                          jpegQual + ".jpg";
         FileOutputStream fos = new FileOutputStream(tempStr);
@@ -659,7 +661,9 @@ class TJBench {
     System.out.println("-benchtime <t> = Run each benchmark for at least <t> seconds (default = 5.0)");
     System.out.println("-warmup <w> = Execute each benchmark <w> times to prime the cache before");
     System.out.println("     taking performance measurements (default = 1)");
-    System.out.println("-componly = Stop after running compression tests.  Do not test decompression.\n");
+    System.out.println("-componly = Stop after running compression tests.  Do not test decompression.");
+    System.out.println("-nowrite = Do not write reference or output images (improves consistency");
+    System.out.println("     of performance measurements.)\n");
     System.out.println("NOTE:  If the quality is specified as a range (e.g. 90-100), a separate");
     System.out.println("test will be performed for all quality values in the range.\n");
     System.exit(1);
@@ -817,6 +821,8 @@ class TJBench {
           }
           if (argv[i].equalsIgnoreCase("-componly"))
             compOnly = true;
+          if (argv[i].equalsIgnoreCase("-nowrite"))
+            write = false;
           if (argv[i].equalsIgnoreCase("-warmup") && i < argv.length - 1) {
             int temp = -1;
             try {

tjbench.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (C)2009-2015 D. R. Commander.  All Rights Reserved.
+ * Copyright (C)2009-2016 D. R. Commander.  All Rights Reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
@@ -46,7 +46,7 @@
 #define _throwbmp(m) _throw(m, bmpgeterr())
 
 int flags=TJFLAG_NOREALLOC, componly=0, decomponly=0, doyuv=0, quiet=0,
-	dotile=0, pf=TJPF_BGR, yuvpad=1, warmup=1;
+	dotile=0, pf=TJPF_BGR, yuvpad=1, warmup=1, write=1;
 char *ext="ppm";
 const char *pixFormatStr[TJ_NUMPF]=
 {
@@ -224,7 +224,7 @@ int decomp(unsigned char *srcbuf, unsigned char **jpegbuf,
 		snprintf(tempstr, 1024, "%s_%s%s_%s.%s", filename, subName[subsamp],
 			qualstr, sizestr, ext);
 
-	if(savebmp(tempstr, dstbuf, scaledw, scaledh, pf,
+	if(write && savebmp(tempstr, dstbuf, scaledw, scaledh, pf,
 		(flags&TJFLAG_BOTTOMUP)!=0)==-1)
 		_throwbmp("saving bitmap");
 	ptr=strrchr(tempstr, '.');
@@ -259,7 +259,7 @@ int decomp(unsigned char *srcbuf, unsigned char **jpegbuf,
 					dstbuf[pitch*row+col]
 						=abs(dstbuf[pitch*row+col]-srcbuf[pitch*row+col]);
 		}
-		if(savebmp(tempstr, dstbuf, w, h, pf,
+		if(write && savebmp(tempstr, dstbuf, w, h, pf,
 			(flags&TJFLAG_BOTTOMUP)!=0)==-1)
 			_throwbmp("saving bitmap");
 	}
@@ -422,7 +422,7 @@ int fullTest(unsigned char *srcbuf, int w, int h, int subsamp, int jpegqual,
 			printf("                  Output bit stream:  %f Megabits/sec\n",
 				(double)totaljpegsize*8./1000000.*(double)iter/elapsed);
 		}
-		if(tilew==w && tileh==h)
+		if(tilew==w && tileh==h && write)
 		{
 			snprintf(tempstr, 1024, "%s_%s_Q%d.jpg", filename, subName[subsamp],
 				jpegqual);
@@ -756,7 +756,9 @@ void usage(char *progname)
 	printf("-benchtime <t> = Run each benchmark for at least <t> seconds (default = 5.0)\n");
 	printf("-warmup <w> = Execute each benchmark <w> times to prime the cache before\n");
 	printf("     taking performance measurements (default = 1)\n");
-	printf("-componly = Stop after running compression tests.  Do not test decompression.\n\n");
+	printf("-componly = Stop after running compression tests.  Do not test decompression.\n");
+	printf("-nowrite = Do not write reference or output images (improves consistency of\n");
+	printf("           performance measurements.)\n\n");
 	printf("NOTE:  If the quality is specified as a range (e.g. 90-100), a separate\n");
 	printf("test will be performed for all quality values in the range.\n\n");
 	exit(1);
@@ -906,6 +908,7 @@ int main(int argc, char *argv[])
 				}
 			}
 			if(!strcasecmp(argv[i], "-componly")) componly=1;
+			if(!strcasecmp(argv[i], "-nowrite")) write=0;
 		}
 	}