From e98dde27ef774cac5a92db754cd97ff33dfef07f Mon Sep 17 00:00:00 2001
From: Rob Pike <r@golang.org>
Date: Fri, 7 Aug 2009 10:39:45 -0700
Subject: [PATCH] timing updates after 6g change for efficient division by
 powers of two

R=rsc
DELTA=25  (23 added, 0 deleted, 2 changed)
OCL=32873
CL=32875
---
 test/bench/spectral-norm-parallel.go |  2 +-
 test/bench/timing.log                | 23 +++++++++++++++++++++++
 test/bench/timing.sh                 |  2 +-
 3 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/test/bench/spectral-norm-parallel.go b/test/bench/spectral-norm-parallel.go
index 9e7f33885f..68aaedea66 100644
--- a/test/bench/spectral-norm-parallel.go
+++ b/test/bench/spectral-norm-parallel.go
@@ -47,7 +47,7 @@ var n = flag.Int("n", 2000, "count")
 var nCPU = flag.Int("ncpu", 4, "number of cpus")
 
 func evalA(i, j int) float64 {
-	return 1 / float64(((i + j)*(i + j + 1)>>1+ i + 1));
+	return 1 / float64(((i + j)*(i + j + 1)/2 + i + 1));
 }
 
 type Vec []float64
diff --git a/test/bench/timing.log b/test/bench/timing.log
index 43293665d5..8fbf43a444 100644
--- a/test/bench/timing.log
+++ b/test/bench/timing.log
@@ -92,3 +92,26 @@ pidigits 10000
 	gc pidigits	77.69u 0.14s 78.18r
 	gc_B pidigits	74.26u 0.18s 75.41r
 	gc_B pidigits	68.48u 0.20s 69.31r   # special case: no bounds checking in bignum
+
+August 7 2009
+
+# New gc does better division by powers of 2.  Significant improvements:
+
+spectral-norm 5500
+	gcc -O2 spectral-norm.c -lm	11.50u 0.00s 11.50r
+	gccgo -O2 spectral-norm.go	12.02u 0.00s 12.02r
+	gc spectral-norm	23.98u 0.00s 24.00r	# new time is 0.48 times old time, 52% faster
+	gc_B spectral-norm	23.71u 0.01s 23.72r	# ditto
+	gc spectral-norm-parallel	24.04u 0.00s 6.26r  # /2 put back.  note: 4x faster (on r70, idle)
+
+k-nucleotide 1000000
+	gcc -O2 -I/usr/include/glib-2.0 -I/usr/lib/glib-2.0/include k-nucleotide.c -lglib-2.0	10.82u 0.04s 10.87r
+	gccgo -O2 k-nucleotide.go	22.73u 0.89s 23.63r
+	gc k-nucleotide	15.97u 0.03s 16.04r
+	gc_B k-nucleotide	15.86u 0.06s 15.93r	# 8.5% faster, but probably due to weird cache effeccts in previous version
+
+pidigits 10000
+	gcc -O2 pidigits.c -lgmp	2.58u 0.00s 2.58r
+	gc pidigits	71.24u 0.04s 71.28r	# 8.5% faster
+	gc_B pidigits	71.25u 0.03s 71.29r	# 4% faster
+
diff --git a/test/bench/timing.sh b/test/bench/timing.sh
index a8cc9e0039..233e381c62 100755
--- a/test/bench/timing.sh
+++ b/test/bench/timing.sh
@@ -121,7 +121,7 @@ pidigits() {
 
 case $# in
 0)
-	run="fasta revcom nbody binarytree fannkuch regexdna spectralnorm knucleotide mandelbrot meteor pidigits"
+	run="fasta revcomp nbody binarytree fannkuch regexdna spectralnorm knucleotide mandelbrot meteor pidigits"
 	;;
 *)
 	run=$*
-- 
2.48.1