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标题: ZZ 老高(Donald E.Knuth)对多核的看法，偶很认同 [打印本页]

作者: prolj 时间: 2008-05-16 21:20
标题: ZZ 老高(Donald E.Knuth)对多核的看法，偶很认同
http://www.informit.com/articles/article.aspx?p=1193856

Andrew: Vendors of multicore processors have expressed frustration at the
difficulty of moving developers to this model. As a former professor, what
thoughts do you have on this transition and how to make it happen? Is it a
question of proper tools, such as better native support for concurrency in
languages, or of execution frameworks? Or are there other solutions?

Donald: I don't want to duck your question entirely. I might as well flame a
bit about my personal unhappiness with the current trend toward multicore
architecture. To me, it looks more or less like the hardware designers have
run out of ideas, and that they're trying to pass the blame for the future
demise of Moore's Law to the software writers by giving us machines that work
faster only on a few key benchmarks! I won't be surprised at all if the whole
multithreading idea turns out to be a flop, worse than the "Titanium"
approach that was supposed to be so terrific-until it turned out that the
wished-for compilers were basically impossible to write.

Let me put it this way: During the past 50 years, I've written well over a
thousand programs, many of which have substantial size. I can't think of even
five of those programs that would have been enhanced noticeably by
parallelism or multithreading. Surely, for example, multiple processors are
no help to TeX.[1]

How many programmers do you know who are enthusiastic about these promised
machines of the future? I hear almost nothing but grief from software people,
although the hardware folks in our department assure me that I'm wrong.

I know that important applications for parallelism exist-rendering graphics,
breaking codes, scanning images, simulating physical and biological
processes, etc. But all these applications require dedicated code and
special-purpose techniques, which will need to be changed substantially every
few years.

Even if I knew enough about such methods to write about them in TAOCP, my
time would be largely wasted, because soon there would be little reason for
anybody to read those parts. (Similarly, when I prepare the third edition of
Volume 3 I plan to rip out much of the material about how to sort on magnetic
tapes. That stuff was once one of the hottest topics in the whole software
field, but now it largely wastes paper when the book is printed.)

The machine I use today has dual processors. I get to use them both only when
I'm running two independent jobs at the same time; that's nice, but it
happens only a few minutes every week. If I had four processors, or eight, or
more, I still wouldn't be any better off, considering the kind of work I
do-even though I'm using my computer almost every day during most of the day.
So why should I be so happy about the future that hardware vendors promise?
They think a magic bullet will come along to make multicores speed up my kind
of work; I think it's a pipe dream. (No-that's the wrong metaphor!
"Pipelines" actually work for me, but threads don't. Maybe the word I want is
"bubble.")

From the opposite point of view, I do grant that web browsing probably will
get better with multicores. I've been talking about my technical work,
however, not recreation. I also admit that I haven't got many bright ideas
about what I wish hardware designers would provide instead of multicores, now
that they've begun to hit a wall with respect to sequential computation. (But
my MMIX design contains several ideas that would substantially improve the
current performance of the kinds of programs that concern me most-at the cost
of incompatibility with legacy x86 programs.)

[ 本帖最后由 prolj 于 2008-5-17 13:10 编辑 ]

作者: run_xiao2000 时间: 2008-05-17 13:12
翻译一哈，看得累呢

作者: prolj 时间: 2008-05-17 13:14
直白的说就是，以前大家都是修炼武功比比谁更厉害，知道大家都很厉害了，某些人就搞起了七星北斗阵，7个打1个。
老高认为应该继续个人修炼，我觉得一个核很牛X的话，对于多个核是很有帮助的

作者: run_xiao2000 时间: 2008-05-17 13:57
天下局势，分久必合，合久必分，呵呵

作者: system888net 时间: 2008-05-17 14:00

原帖由 prolj 于 2008-5-17 13:14 发表
直白的说就是，以前大家都是修炼武功比比谁更厉害，知道大家都很厉害了，某些人就搞起了七星北斗阵，7个打1个。
老高认为应该继续个人修炼，我觉得一个核很牛X的话，对于多个核是很有帮助的

不错,很人性化的说法

作者: system888net 时间: 2008-05-17 14:01

原帖由 run_xiao2000 于 2008-5-17 13:57 发表
天下局势，分久必合，合久必分，呵呵

有理,技术的发展常常有轮回的现象发生.

作者: run_xiao2000 时间: 2008-05-17 14:17
LZ看了老高的TAOCP没？

作者: prolj 时间: 2008-05-17 14:19
大三的时候浏览过1、3，当时觉得第2卷实在没意思，跟没看一样

作者: run_xiao2000 时间: 2008-05-17 14:27
第2卷讲随机数，看得很是头疼，数学跟不上，我也没坚持下来，而且感觉翻译的不太好。（没有冒犯前辈的意思

）

作者: jamesr 时间: 2008-05-17 14:34
提示: 作者被禁止或删除内容自动屏蔽

作者: prolj 时间: 2008-05-17 14:41

原帖由 jamesr 于 2008-5-17 14:34 发表
有人研究反向超线程吗？说不定能够代替Power6。

—— 前面提到，利用多核心不能提高单线程程序性能。利用反向超线程，可以在微观上利用多个核心并行运算一些可以并行的指令组，实质上是线程共享执行单元。但是需要特定的处理器才能支持反向超线程。

龙芯弄了没有？支持龙芯上最先进的技术，打破m米国科技垄断。

作者: jamesr 时间: 2008-05-17 15:16
提示: 作者被禁止或删除内容自动屏蔽

作者: prolj 时间: 2008-05-17 15:23
标题: 回复 #14 jamesr 的帖子
自己国家的东西，除了支持，我们别无选择，别指望老外帮我们。
既然不是局内人，也只有看热闹的份，毕竟作决定和执行的人都不是你。
大家一起民间爱好也是不错的

关心自己脚下的每一步比期盼别人的脚步要好

作者: prolj 时间: 2008-05-17 15:24
标题: 回复 #12 run_xiao2000 的帖子
一起做，有个照应

作者: Roemer 时间: 2008-05-17 22:49
Donald E.Knuth传奇式人物~~

作者: paul356 时间: 2008-05-19 15:57
怎么看不到，要回复一个么，试一下吧

作者: cnshibo 时间: 2008-05-19 16:59
标题: 回复 #18 paul356 的帖子
为什么会看不到呢？

作者: wealk 时间: 2008-05-21 09:00
帖子呢怎么没了，被禁了？

作者: millet.fr 时间: 2008-05-21 16:49
太可惜了，这么好的帖子，竟然看不了

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