1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17

[#11#ljy@ljydeiMac ~/cpp_pro]$g++ --version
Configured with: --prefix=/Library/Developer/CommandLineTools/usr --with-gxx-include-dir=/usr/include/c++/4.2.1
Apple LLVM version 6.0 (clang-600.0.56) (based on LLVM 3.5svn)
Target: x86_64-apple-darwin14.0.0
Thread model: posix
[#12#ljy@ljydeiMac ~/cpp_pro]$go version
go version go1.4.2 darwin/amd64

C++ 成绩：
real    0m16.791s
user    0m16.093s
sys 0m0.687s

golang 成绩：
real    0m26.582s
user    0m26.393s
sys 0m0.161s

1
2
3
4
5
6
7
8
9
10
11
12

(pprof) top10
Total: 2525 samples
     298  11.8%  11.8%      345  13.7% runtime.mapaccess1_fast64
     268  10.6%  22.4%     2124  84.1% main.FindLoops
     251   9.9%  32.4%      451  17.9% scanblock
     178   7.0%  39.4%      351  13.9% hash_insert
     131   5.2%  44.6%      158   6.3% sweepspan
     119   4.7%  49.3%      350  13.9% main.DFS
      96   3.8%  53.1%       98   3.9% flushptrbuf
      95   3.8%  56.9%       95   3.8% runtime.aeshash64
      95   3.8%  60.6%      101   4.0% runtime.settype_flush
      88   3.5%  64.1%      988  39.1% runtime.mallocgc

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17

(pprof) list DFS
Total: 2525 samples
ROUTINE ====================== main.DFS in /home/rsc/g/benchgraffiti/havlak/havlak1.go
   119    697 Total samples (flat / cumulative)
     3      3  240: func DFS(currentNode *BasicBlock, nodes []*UnionFindNode, number map[*BasicBlock]int, last []int, current int) int {     1      1  241:     nodes[current].Init(currentNode, current)
     1     37  242:     number[currentNode] = current
     .      .  243:
     1      1  244:     lastid := current
    89     89  245:     for _, target := range currentNode.OutEdges {     9    152  246:             if number[target] == unvisited {     7    354  247:                     lastid = DFS(target, nodes, number, last, lastid+1)
     .      .  248:             }
     .      .  249:     }
     7     59  250:     last[number[currentNode]] = lastid
     1      1  251:     return lastid
(pprof)

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32

调优前
$time ./havlak1
# of loops: 76000 (including 1 artificial root node)

real    0m21.686s
user    0m21.578s
sys 0m0.111s

按照上面方法调优后
time ./havlak2
# of loops: 76000 (including 1 artificial root node)

real    0m12.588s
user    0m12.486s
sys 0m0.103s

对比我们上一次测试的源代码修改了之后的成绩，可以看到与C++的成绩非常接近了。(GO:26s,CPP:16s)
time ./go_pro
Welcome to LoopTesterApp, Go edition
Constructing Simple CFG...
15000 dummy loops
Constructing CFG...
Performing Loop Recognition
1 Iteration
Another 50 iterations...
..................................................
# of loops: 76000 (including 1 artificial root node)

real    0m18.447s
user    0m18.297s
sys 0m0.134s