原生数组、std::array、std::vector访问性能对比
先上结论：
std::vector的at()操作最慢。其时间约达其他访问方式的2~4倍。原生数组和std::vector的[]访问较快。std::array的访问速度介于中间，约是原生的2倍。
具体测试方法：
主要测试读取和赋值访问，结果中：
t1 - std::array的at()时间
t2 - std::array的[]时间
t3 - 原生数组时间
t4 - std::vector的at()时间
t2 - std::vector的[]时间
访问：
auto now() {
struct timeval tvt;
gettimeofday(&tvt, 0);
return tvt.tv_sec * 1000000 + tvt.tv_usec;
}
void test()
{
std::array
int times = 1000000;
auto t1 = now();
for (int i = 0; i < times; ++i)
{
a.at(1);
}
std::cout << "t1:" << now() - t1 << std::endl;
auto t2 = now();
for (int i = 0; i < times; ++i)
{
a[1];
}
std::cout << "t2:" << now() - t2 << std::endl;
int b[10] = {0};
auto t3 = now();
for (int i = 0; i < times; ++i)
{
b[1];
}
std::cout << "t3:" << now() - t3 << std::endl;
std::vector
auto t4 = now();
for (int i = 0; i < times; ++i)
{
v.at(1);
}
std::cout << "t4:" << now() - t4 << std::endl;
auto t5 = now();
for (int i = 0; i < times; ++i)
{
v[1];
}
std::cout << "t5:" << now() - t5 << std::endl;
}
int main()
{
for (int i = 0; i < 10; ++i)
{
std::cout << "n:" << i << std::endl;
test();
}
}
数据结果：
n:0
t1:3823
t2:3925
t3:2444
t4:8292
t5:1757
n:1
t1:3939
t2:3914
t3:1997
t4:8247
t5:1764
n:2
t1:3846
t2:3915
t3:2169
t4:8260
t5:1764
n:3
t1:3761
t2:3895
t3:2161
t4:8376
t5:1869
n:4
t1:3868
t2:3916
t3:2291
t4:8303
t5:1763
n:5
t1:3788
t2:3928
t3:2448
t4:8241
t5:1761
n:6
t1:3760
t2:3914
t3:2193
t4:8336
t5:1762
n:7
t1:3876
t2:3908
t3:2159
t4:8255
t5:1805
n:8
t1:3869
t2:4111
t3:2488
t4:8283
t5:1865
n:9
t1:3737
t2:3909
t3:2271
t4:8292
t5:1761
赋值：
#include
#include
#include
#include
auto now() {
struct timeval tvt;
gettimeofday(&tvt, 0);
return tvt.tv_sec * 1000000 + tvt.tv_usec;
}
void test()
{
std::array
int times = 1000000;
auto t1 = now();
for (int i = 0; i < times; ++i)
{
a.at(1) = 1;
}
std::cout << "t1:" << now() - t1 << std::endl;
auto t2 = now();
for (int i = 0; i < times; ++i)
{
a[1] = 1;
}
std::cout << "t2:" << now() - t2 << std::endl;
int b[10] = {0};
auto t3 = now();
for (int i = 0; i < times; ++i)
{
b[1] = 1;
}
std::cout << "t3:" << now() - t3 << std::endl;
std::vector
auto t4 = now();
for (int i = 0; i < times; ++i)
{
v.at(1) = 1;
}
std::cout << "t4:" << now() - t4 << std::endl;
auto t5 = now();
for (int i = 0; i < times; ++i)
{
v[1] = 1;
}
std::cout << "t5:" << now() - t5 << std::endl;
}
int main()
{
for (int i = 0; i < 10; ++i)
{
std::cout << "n:" << i << std::endl;
test();
}
}
数据结果：
n:0
t1:4032
t2:4057
t3:2204
t4:8628
t5:2005
n:1
t1:3950
t2:4119
t3:2292
t4:8311
t5:2004
n:2
t1:3948
t2:4061
t3:2366
t4:8305
t5:2005
n:3
t1:3956
t2:4057
t3:2144
t4:8496
t5:2007
n:4
t1:3853
t2:4058
t3:2213
t4:8343
t5:2116
n:5
t1:4001
t2:4056
t3:2091
t4:8460
t5:2008
n:6
t1:3968
t2:4175
t3:2092
t4:8310
t5:2005
n:7
t1:3963
t2:4130
t3:1819
t4:8408
t5:2038
n:8
t1:4138
t2:4190
t3:2188
t4:8452
t5:2054
n:9
t1:3964
t2:4058
t3:2328
t4:8375
t5:2007