matlab中double 和single數據類型的差異

matlab中double 和single數據類型的差異

matlab中double 和single數據類型的差異

double數據類型佔用8個字節，single數據類型佔4個字節。因此用single會更快一些。（能夠這麼理解，就像你作8位數乘法跟作4位數乘法同樣～確定作4位數的運算更快一些嘛）

 

a=randn(3,3)

a =

    0.8404   -0.5445    0.4900
   -0.8880    0.3035    0.7394
    0.1001   -0.6003    1.7119

>> b=single(a)

b =

    0.8404   -0.5445    0.4900
   -0.8880    0.3035    0.7394
    0.1001   -0.6003    1.7119

>> c=randn(3,3);
>> tic,a*c,toc;

ans =

    0.5899    2.1930   -1.6388
   -1.0974   -0.8179   -1.1239
   -0.1730    2.4243   -4.2069

Elapsed time is 0.199251 seconds.
>> tic,b*c,toc;

ans =

    0.5899    2.1930   -1.6388
   -1.0974   -0.8179   -1.1239
   -0.1730    2.4243   -4.2069

Elapsed time is 0.002739 seconds.
>> class(a)

ans =

double

>> class(b)

ans =

single

可見，single類型數據運算速度明顯比double型數據快不少。