t****t
发帖数: 6806 | 1 make sure your optimization problem can converge? |
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j****i
发帖数: 305 | 2 Does the gcc compiler optimize the following code?
std::vector v(5);
std::vector::iterator it;
for(it = v.begin(); it != v.end(); it++)
Or is it faster to do this:
std::vector v(5);
std::vector::iterator it;
std::vector::iterator end(v.end());
for(it = v.begin(); it != end; ++it)
Note that the temp variable end, and the preincrement of it.
I was reading Exceptional C++ and it says the second way is faster, but I'm
wondering if the comipler has gotten better since the boo |
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B*******g
发帖数: 1593 | 3 The 2 differences both make sense to me.
v.end() is called each loop, which is unnecessary.
++ it does not make a copy of iterator compared to it++.
I don't think compiler should optimize either of those, I could be wrong tho
. |
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d****p
发帖数: 685 | 4 It is a good habit to do so - expert C++ coders write this way in boost
libraries.
However, most mainstream compilers are able to achieve optimal code in even
the 1st situation. So it does not matter actually. |
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p***o
发帖数: 1252 | 5 Many optimizations packages like mosek and cplex have interfaces
to c/c++ and other popular languages. |
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f*********e
发帖数: 10 | 6 It's a piece of code to test if you can optimize it so it runs faster than
the current implementation. |
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f*********e
发帖数: 10 | 7 this is one of the interview questions. I cannot figure it out. So put it
here and see if any gurus have any ideas to optimize it to run faster. |
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L***n
发帖数: 6727 | 8 i guess they are testing you some basic optimization techniques like loop
unrolling, etc |
|
os
发帖数: 81 | 9 Posted from Open Collections Program@LISF
Download Address: http://www.lanken.com/forum/viewtopic.php?t=85
Implementing SSH: Strategies for Optimizing the Secure Shell.
by Himanshu Dwivedi.
ISBN: 0-471-45880-5, 402 Pages, October 2003.
Prevent unwanted hacker attacks! This detailed guide
will show you how to strengthen your company system!/s
defenses, keep critical data secure, and add to the
functionality of your network by deploying SSH.
Security expert Himanshu Dwivedi shows you ways |
|
j****0
发帖数: 20 | 10 打开一个E-Mail中的Link，突然电脑就安全检查起来，说有大量病毒，要安装Windows
Security Optimizer，我就安装了，重启后说这个软件是试用版，已过期，要购买。然
后一打开网页，这东东就跳出来，让你购买，你Deny的话，网页就关掉了，所以网也上
不了，只能借用其他电脑。
1）查了最近安装的软件，想删除，但找不到。怎么能够把它删了？
2）如何在重启电脑的时候，让一些软件不自动运行？
谢谢各位大侠。 |
|
s******s
发帖数: 13035 | 11 最后我还是找了genscript要了一个quote, 1.1kb的大概$400,和你
这个差不多。不过还是不如gblock便宜，我直接拿着genscript optimize
好的序列扔给idt了 |
|
s********w
发帖数: 487 | 12 background:
在国内sjtu读的是化工专业，本科的研究方向是 锂离子电池负极材料，master的研究方
向是 氧化锌及其杂化薄膜。当时对自己的研究方向很没有兴趣。因为以前的研究方向
都比较偏向于材料，而我本人比较喜欢数学，物理，化工原理等科目，工程类的方向。
不太喜欢纯粹理科类的研究（偏化学的）
所以master毕业后去公司做的是 information system相关的project（大家都说我有点
脑抽
，现在想想也有点后悔当初这样的选择），平时一直要programming，也不讨厌program
ming。然后最近在做sap相关的configuration，abap编程等相关project。
去年的这个时候，突然有想出国的冲动，于是在网上查到了以下这些research area，而
且还比较感兴趣，更重要的是，感觉可以结合我以前化工的background，以及一些工作
经验。但是不知道它们相互之间的区别，以及未来的出路。
process control / process design/ process optimization
在网上还看到一个是process s |
|
m***i
发帖数: 30 | 13 对于一个过程来说，process design是第一个层次，需要较强的化工背景。
狭义的process control是第二个层次，通过控制实现具体的设定目标（比如温度控制
在多少）。所针对的是一个一个模型，表达成数学形式，就不太需要过程知识了，而是
设计算法（通常算法也是现成的，只是调参数）。如果算法需要模型，就可以研究其机
理，或者通过数据得到数学模型。
process optimization是更高的层次，是通过设计局部的设定值和运行方案来优化全局
目标（例如效益）。这对过程知识要求比较少少，主要也是优化算法。
广义的process control，还包括一些其他的部分，比如系统性能评价、故障分析、报
警系统设计、软测量等等，这里就有process safety的问题了。
如果说国内背景的话，这些方向主要需要的都是自动化的知识。 |
|
s********w
发帖数: 487 | 14 background:
在国内sjtu读的是化工专业，本科的研究方向是 锂离子电池负极材料，master的研究方
向是 氧化锌及其杂化薄膜。当时对自己的研究方向很没有兴趣。因为以前的研究方向
都比较偏向于材料，而我本人比较喜欢数学，物理，化工原理等科目，工程类的方向。
不太喜欢纯粹理科类的研究（偏化学的）
所以master毕业后去公司做的是 information system相关的project（大家都说我有点
脑抽
，现在想想也有点后悔当初这样的选择），平时一直要programming，也不讨厌program
ming。然后最近在做sap相关的configuration，abap编程等相关project。
去年的这个时候，突然有想出国的冲动，于是在网上查到了以下这些research area，而
且还比较感兴趣，更重要的是，感觉可以结合我以前化工的background，以及一些工作
经验。但是不知道它们相互之间的区别，以及未来的出路。
process control / process design/ process optimization
在网上还看到一个是process s... 阅读全帖 |
|
m***i
发帖数: 30 | 15 对于一个过程来说，process design是第一个层次，需要较强的化工背景。
狭义的process control是第二个层次，通过控制实现具体的设定目标（比如温度控制
在多少）。所针对的是一个一个模型，表达成数学形式，就不太需要过程知识了，而是
设计算法（通常算法也是现成的，只是调参数）。如果算法需要模型，就可以研究其机
理，或者通过数据得到数学模型。
process optimization是更高的层次，是通过设计局部的设定值和运行方案来优化全局
目标（例如效益）。这对过程知识要求比较少少，主要也是优化算法。
广义的process control，还包括一些其他的部分，比如系统性能评价、故障分析、报
警系统设计、软测量等等，这里就有process safety的问题了。
如果说国内背景的话，这些方向主要需要的都是自动化的知识。 |
|
|
t*****o
发帖数: 74 | 17 Can anyone refer some good books or website on Fortran code optimization?
i.e. how to improve the code efficiency
I know if there two loop, one is 10 and another is 1000
do i = 1, 10
do j = 1, 1000
...
end do
end do
is better than
do i = 1, 1000
do j = 1, 10
...
end do
end do
Is there any other way to improve the efficiency? |
|
x*y
发帖数: 364 | 18 The compiler group of CS in my university are developing HPCVIEW to optimize
the code. I tested it on my Fortran code on a SGI origin machine last year,
it's really cool, code can even be much fater if we pass arrays from
subroutine to subroutine in good way. It will be really great if this tool
come to be in use. |
|
f***n
发帖数: 6 | 19 Just for fun, I run bench.m on my Barton
System:
Barton @ 1.4GHz (reason: my memory is PC2100, so Barton downspeed :-( )
DDR ram 512MB
GF 4 MX440.
Matlab 6.1
Win2k pro.
LU decomp: 0.51s
Then I replace the ATLAS library with the one claimed to be optimized for
AthlonXP
(see here: http://www.econ.ucsd.edu/~ksheppar/matlab/MatlabAtlas.htm)
However, there is NO speedup observed, LU costs even 0.71s!!!
So I switch back to default ATLAS)
I am also curious that if any existent package can use SSE2's a |
|
a*******a
发帖数: 33 | 20
Intel compiler can do SSE2 optimization |
|
l*****a
发帖数: 119 | 21 co-ask. lz也做optimization? |
|
p*n
发帖数: 134 | 22 【 以下文字转载自 EE 讨论区 】
发信人: pen (谢谢你), 信区: EE
标 题: 问个optimization的问题
发信站: BBS 未名空间站 (Mon Oct 23 21:03:40 2006), 转信
max \sum_i c_i |x_i|
s.t. A x = b
有什么方法可以用来解这个优划问题么? |
|
j*****n
发帖数: 1545 | 23 我想找一个解x, min(f(x))，同时 max (h(x))。 当然可以把max(h(x))转化为 min(h'
(x))， 就变成了同时最优化两个方程的问题。
这种问题怎么解，我感觉应该可以变成 constrained optimization 来搞。或者能不能
弄成 迭代求解， 比如每次循环的时候，先min(f(x))再min(h'(x)) ，像 kmeans, EM那
种思想。
大家给点意见吧，谢谢 |
|
S*M
发帖数: 536 | 24 search multi-objective optimization
they are many approaches on hand existing now
h'
EM那 |
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l***e
发帖数: 10 | 25 To be exact, the optimization problem min f(x)= 1/2 x' H x- sum(abs(x)). x
is vector, every component lies in [-c, c] and the sum of x is zero. |
|
a***o
发帖数: 969 | 26 【 以下文字转载自 Mathematics 讨论区 】
发信人: amigo (阿米哥), 信区: Mathematics
标 题: 有啥好的optimization的c/c++库可以用
发信站: BBS 未名空间站 (Mon Dec 31 04:02:58 2007), 转信
特别是open source，
非线性优化的
3x |
|
f*******a
发帖数: 80 | 27 Hi Folks, Does someone know a book on optimization or estimation over
complex domain? The books I have in hand carry out the analysis in the real
domain only. However, the problem I am working on uses phasor/cplx nmber. I
am from time to time confused on the use of transpose and conjugate
transpose.
Thank you. |
|
D******n
发帖数: 2836 | 28 the parameters i am going to optimize should be summed up to 1 |
|
a****f
发帖数: 944 | 29 I want to minimize the energy E=f(p;...). p is a vector containing a set of
parameters.
I set initial values of each element in p based on some prior knowledge.
Then I use fmincon to find the optimal p that minimizes E.
Some elements in p are constrained in a range so I set the constraints
according to the syntax of fmincon.
The result is, the elements in p without constraints do not change (the same
as initial values), the elements that are initially in their constraints do
not change either, o |
|
a****f
发帖数: 944 | 30 Thank you.
I tried and it only ran 2 iterations before it was terminated. The 'max
constraint' value was -6.9 in both iterations. directional derivative and
first-order optimality are both 0. Is this normal?
What does max constraint mean? should it be close to 0 at the final
iteration? I used inequality constraint, something like Ax
document |
|
|
w******u
发帖数: 156 | 32 【 以下文字转载自 Mathematics 讨论区,原文如下 】
发信人: wangmumu (咕噜), 信区: Mathematics
标 题: Maximum Likelihood Optimization
发信站: Unknown Space - 未名空间 (Mon Oct 6 12:28:22 2003) WWW-POST
I need to estimate a time series model using maximum likelihood method. My
model is very similar to GARCH. Is there any package (MatLab) that will allow
me to modify the standard model and do estimation for me? Or I will have to
write my own program to do it? I found out usually people use BHHH method to
do it. Does anybody know |
|
z********u
发帖数: 30 | 33 在infinite horizon model, the chamley-jadd result tells that the optimal
capital taxation result is ZERO, but in OLD model, this result depends on
the utility functiont.
As we know, in circumstances of infinite horizon model, the distortion of
positive capital taxation means otherwise increasing consumption taxation
rate,
so, what is the intuition of failure of Chamley-judd result in OLD?
Thanks... |
|
l**********t
发帖数: 5754 | 34 I'm interested in using stochastic programming in an optimization problme.
Could someone with experience in this area recommend softwares/C++ libraries
? Does SAS or MatLab have packages for stochastic programming? Many thanks. |
|
i**M
发帖数: 108 | 35 【 以下文字转载自 Mathematics 讨论区 】
发信人: iFEM (莫扎特的音符), 信区: Mathematics
标 题: optimization question
发信站: BBS 未名空间站 (Wed May 25 16:52:30 2011, 美东)
Suppose c(p) is a monotonically dreasing function as shown in the picture. c
is the cost and p is the risk. As p increases, the risk is increasing but
the cost is decreasing. The question is how to minimize the cost and keep
the risk not too high? Thanks! |
|
z****e
发帖数: 438 | 36 what do you mean by saying "keep the risk not too high"? This is the
constraint for your optimization problem and you have to be very specific
about it. |
|
i**M
发帖数: 108 | 37 The cost function is a strictly decreasing fuction of risk. Ppl told me that
I should use utility function to solve this problem. But I have no idea how
to construct an efficient utility function.
It's not a typical optimization problem, coz, I only need to find a balance
of risk and cost.
Thanks a lot |
|
w******s
发帖数: 60 | 38 I do not want to offend, but I have to say that it is purely a joke for Gu to
win any prestigious awards in theoretical computer science. I happened to
carry out research in optimization (esp. in its theory part). I am also a fan
of evolutionary algorithms, though not much theory work there. Gu's
publication in theory is pretty averge (those journals are not leading in
theory). You can easily find theory professors with much stronger papers even
in a 3-tier research univ in US. He also has many |
|
D*******a
发帖数: 3688 | 39 我觉得steve boyd的那本convex optimization还不错，覆盖比较广，而且免费
想深入的，就看bertsimas/bertsekas的 |
|
g******u
发帖数: 3060 | 40 optimal control有很多书吧.
convex实在看不懂. |
|
D*******a
发帖数: 3688 | 41 optimal control经典好像也就三本
lee and marcus
michael athans
bryson and ho |
|
f*****l
发帖数: 82 | 42 Not so good, I think....
This is very similar to IE or Optimization in CS.... Why don't you direc
tly pursue IE dept? Hehe, wired
and
of
variety |
|
f*****l
发帖数: 82 | 43 Oh... I am wrong... UCLA does not have IE Dept.... One of the professors
in this group is the author of convex optimization, hmmm |
|
a***o
发帖数: 969 | 44 【 以下文字转载自 Mathematics 讨论区 】
发信人: amigo (阿米哥), 信区: Mathematics
标 题: 有啥好的optimization的c/c++库可以用
发信站: BBS 未名空间站 (Mon Dec 31 04:02:58 2007), 转信
特别是open source，
非线性优化的
3x |
|
g*******g
发帖数: 46 | 45 mMaple 也有此功能
maple还有一个附带的工具包，叫 globle optimization toolbox
据他们吹很牛
matlab, fmincon |
|
X*****r
发帖数: 2521 | 46 SDP是不是要求constraint必须是linear/convex的？
有nonconvex的SDP的global optimization解法吗？
centralized的也行 |
|
m*******t
发帖数: 168 | 47 小弟目前在学习MATLAB编程解决OPTIMIZATION的问题. 比如: support vector machine
, fisher linear discriminant. 目前,没有找到一本适合学习的书.
求高手推荐一本. 谢谢! |
|
l*********2
发帖数: 95 | 48 最近在用Genesis做结构优化，从来没有接触过topology optimization方面的理论，不
知道版上的前辈可否推荐一些这方面的书籍/资料呢？感谢！ |
|
l*********2
发帖数: 95 | 49 最近在用Genesis做结构优化，从来没有接触过topology optimization方面的理论，不
知道版上的前辈可否推荐一些这方面的书籍/资料呢？感谢！ |
|
c**********r
发帖数: 4 | 50 【 以下文字转载自 CS 讨论区 】
发信人: csresearcher (life for research), 信区: CS
标 题: About QCQP optimization problem
发信站: BBS 未名空间站 (Sun Dec 18 21:03:17 2005)
Does anyone know how to solve the Quadratically Constrained Quadratic
Programming problem? (Suppose the objective and constraint functions are
convex)
Can this be solved in poly-nomial time?
Any link on refereces will be highly appreciated!
Thanks! |
|
