- 分岐予測の失敗 → 5ns
- L1 / L2キャッシュ→ 0.5ns / 7ns
L1 cache reference 0.5 ns
Branch mispredict 5 ns
L2 cache reference 7 ns
Mutex lock/unlock 100 ns
Main memory reference 100 ns
Compress 1K bytes with Zippy 10,000 ns 0.01 ms
Send 1K bytes over 1 Gbps network 10,000 ns 0.01 ms
Read 1 MB sequentially from memory 250,000 ns 0.25 ms
Round trip within same datacenter 500,000 ns 0.5 ms
Disk seek 10,000,000 ns 10 ms
Read 1 MB sequentially from network 10,000,000 ns 10 ms
Read 1 MB sequentially from disk 30,000,000 ns 30 ms
Send packet CA->Netherlands->CA 150,000,000 ns 150 ms
Where1 ns = 10-9 seconds
1 ms = 10-3 seconds
引用: “Numbers Everyone Should Know” from Jeff Dean.
doubleのbit数
MSB・指数・仮数で1bit / 11bit / 52bit
$1.2345 = 12345(\mathrm{mantissa}) \times 10^ {N(\mathrm{exp})}$
