August 2018
Intermediate to advanced
227 pages
4h 16m
Chinese
Content preview from 高效R语言编程
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172
｜
第
8
章
系统但用的是
32
位的
R
，你能访问稍多些的
RAM
（但并没多太多）。现代
系统应该使用
64
位操作系统与
64
位
R
语言。此时
Windows
的内存限制是
8TB
，
UNIX
家族是
128TB
。简单的检测你的系统是否是
64
位的
R
，可执行
下面命令：
.Machine$sizeof.pointer
如果是
64
位的
R
，返回
8
。
为了查询更多细节，使用 help("Memory-limits") 与 help("Memory") 查看
相应帮助页。
练习
这些习题是为了将前面内容归纳成关键的两点。
1.
你正在用
32
位或
64
位的
R
语言？
2.
如果你在用
Windows
，执行 memory.limit() 的结果是什么
?
中央处理器
中央处理单元（
CPU
）或者处理器是计算机的大脑。
CPU
负责执行数值计算。
CPU
速度越快，
R
的执行速度越快。时钟速率（或者时钟频率，
Hz
）是
CPU
执行指令的频率。
CPU
的时钟频率越快，
CPU
在单位时间内执行的指令越
多。
近几年的单个
CPU
的时钟速率几乎无变化，一直在
3.4GHz
周围（见图
8-3
）。
不幸的是，由于
CPU
的内部构架是确定
CPU
性能的关键因素
,
我们不能仅用
CPU
时钟速率比较
CPU
。包
benchmarkme
提供了测试你的系统的函数，并
提供了以前测试基准的数据。
图
8-4
提供了
150
个
CPU
的测试结果。
使用
benchmarkme
包可执行测试并比较你的
CPU
与其他的测试结果。加载
该包，我们可检测你的
CPU
。
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.