From: Rob Pike <r@golang.org>
Date: Tue, 4 Aug 2009 21:07:17 +0000 (-0700)
Subject: improve myrandom() in fasta.
X-Git-Tag: weekly.2009-11-06~980
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=0444da91c032b29eea82919054380bcf6c97f0f3;p=gostls13.git

improve myrandom() in fasta.
add script to automate timing

R=rsc
DELTA=78  (68 added, 0 deleted, 10 changed)
OCL=32729
CL=32732
---

diff --git a/test/bench/fasta.go b/test/bench/fasta.go
index fd31400c81..7919f72045 100644
--- a/test/bench/fasta.go
+++ b/test/bench/fasta.go
@@ -66,7 +66,7 @@ type AminoAcid struct {
 var	lastrandom uint32 = 42
 
 // Random number between 0.0 and 1.0
-func myrandom() float {
+func Zmyrandom() float {
 	const (
 		IM = 139968;
 		IA = 3877;
@@ -74,7 +74,25 @@ func myrandom() float {
 	)
 	lastrandom = (lastrandom * IA + IC) % IM;
 	// Integer to float conversions are faster if the integer is signed.
-	return float(lastrandom) / IM;
+	return float(int32(lastrandom)) / IM;
+}
+
+// TODO: delete this when compiler does the reduction for us
+func
+myrandom() float
+{
+	const (
+		IM = 139968;
+		IA = 3877;
+		IC = 29573;
+		S = 46;
+		IM1 = ((1<<S) + IM) / IM;
+	)
+
+	n := (lastrandom * IA + IC);
+	q := uint32((uint64(n) * IM1) >> S);
+	lastrandom = n - q*IM;
+	return float(int32(lastrandom)) / IM;
 }
 
 func AccumulateProbabilities(genelist []AminoAcid) {
diff --git a/test/bench/timing.log b/test/bench/timing.log
index 71be82ca5d..9f25b573c9 100644
--- a/test/bench/timing.log
+++ b/test/bench/timing.log
@@ -6,13 +6,28 @@ First version of fasta. Translation of fasta.c, fetched from
 	http://shootout.alioth.debian.org/u32q/benchmark.php?test=fasta&lang=gpp&id=4
 
 fasta -n 25000000
-	[gcc -O2 fasta.c	5.98u 0.00s 6.01r]
-	gccgo -O2	8.82u 0.02s 8.85r
-	6g	13.50u 0.02s 13.53r
-	6g -B	12.99u 0.02s 13.02r
+	gcc -O2 fasta.c	5.98u 0.00s 6.01r
+	gccgo -O2 fasta.go	8.82u 0.02s 8.85r
+	6g fasta.go	13.50u 0.02s 13.53r
+	6g -B fata.go	12.99u 0.02s 13.02r
+
+Aug 4 2009
+[added timing.sh]
+
+# myrandom:
+#   hand-written optimization of integer division
+#   use int32->float conversion
+fasta -n 25000000
+	gcc -O2 fasta.c	5.99u 0.00s 6.00r 
+	gccgo -O2 fasta.go	8.82u 0.02s 8.85r
+	gc fasta	10.70u 0.00s 10.77r
+	gc_B fasta	10.09u 0.03s 10.12r
 
 reverse-complement < output-of-fasta-25000000
-	[gcc -O2 reverse-complement.c	2.03u 0.84s 13.04r]
-	gccgo -O2	6.47u 1.14s 15.58r
-	6g	6.55u 1.21s 15.45r
-	6g -B	6.19u 1.26s 15.64r
+	gcc -O2 reverse-complement.c	2.04u 0.94s 10.54r
+	gccgo -O2 reverse-complement.go	6.54u 0.63s 7.17r
+	gc reverse-complement	6.55u 0.70s 7.26r
+	gc_B reverse-complement	6.32u 0.70s 7.10r
+
+nbody -n 50000000
+	gcc -O2 nbody.c	21.33u 0.00s 21.34r
diff --git a/test/bench/timing.sh b/test/bench/timing.sh
new file mode 100755
index 0000000000..f80f247a46
--- /dev/null
+++ b/test/bench/timing.sh
@@ -0,0 +1,38 @@
+#!/bin/sh
+# Copyright 2009 The Go Authors.  All rights reserved.
+# Use of this source code is governed by a BSD-style
+# license that can be found in the LICENSE file.
+
+set -e
+. $GOROOT/src/Make.$GOARCH
+
+gc() {
+	$GC $1.go; $LD $1.$O
+}
+
+gc_B() {
+	$GC -B $1.go; $LD $1.$O
+}
+
+run() {
+	echo -n '	'$1'	'
+	$1
+	shift
+	(/home/r/plan9/bin/time $* 2>&1 >/dev/null) |  sed 's/r.*/r/'
+}
+
+echo 'fasta -n 25000000'
+run 'gcc -O2 fasta.c' a.out 25000000
+#run 'gccgo -O2 fasta.go' a.out -n 25000000	#commented out until WriteString is in bufio
+run 'gc fasta' $O.out -n 25000000
+run 'gc_B fasta' $O.out -n 25000000
+
+echo
+6.out -n 25000000 > x
+echo 'reverse-complement < output-of-fasta-25000000'
+run 'gcc -O2 reverse-complement.c' a.out 25000000 < x
+run 'gccgo -O2 reverse-complement.go' a.out -n 25000000 < x
+run 'gc reverse-complement' $O.out -n 25000000 < x
+run 'gc_B reverse-complement' $O.out -n 25000000 < x
+rm x
+