Archive for September, 2010

20 Linux Server Hardening Security Tips

September 28th, 2010 Comments off

Recommended for SysAdmins:

20 Linux Server Hardening Security Tips.

Why recommend?  i) New & valuable information (nothing obvious), ii) Detailed instructions (mostly) for those who may not be familiar, iii) Written well (writing style does not appear to be a personal blog, but an article of some magazine).

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Inspiring Quote – Nothing is done

September 19th, 2010 Comments off

Nothings is done. Everything in the world remains to be done or done over.

The greatest picture is not yet painted, the greatest play isn’t written, the greatest poem is unsung. There isn’t in all the world a perfect railroad, nor a good government, nor a sound law. Physics, mathematics, and especially the most advanced and exact of the sciences, are being fundamentally revised. Chemistry is just becoming a science; psychology, economics, and sociology are awaiting a Darwin, whose work in turn awaiting an Einstein.

If the rah-rah boys in our colleges could be told this, they might not all be specialists in football, parties, and unearned degrees. They are not told it, however; they are told to learn what is known. This is nothing.

(Lincoln Steffens, 1931)
(quoted from How to Get Ideas by Jack Foster)

This was said about 80 years ago! Yet, it is still relevant today. This quote was something that I have wanted to tell my students if I ever get a chance to…

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Hybrid supercomputer in Los Alamos Nat’l Lab.

September 16th, 2010 Comments off

Scientists want faster, more powerful high-performance supercomputers to simulate complex physical, biological, and socioeconomic systems with greater realism and predictive power. In May, Los Alamos scientists doubled the processing speed of the previously fastest computer.Roadrunner, a new hybrid supercomputer, uses a video game chip to propel performance to petaflop/s speeds capable of more than a thousand trillion calculations per second.”The computer is a speed demon. It will allow us to solve tremendous problems,” said Thomas DAgostino, head of the National Nuclear Security Administration, which oversees nuclear weapons research and maintains the warhead stockpile.The computer might also have many medical and science applications, including developing biofuels or discovering drug therapies.

Continue reading: Computing::Worlds Fastest Computer::Los Alamos Lab.

Categories: Review Tags: ,

Short Review – Eliminating microarchitectural dependency from Architectural Vulnerability

September 14th, 2010 Comments off

There is a paper that is very closely related to our work on RFV. Question is how do they differ?

First terminology. Microarchitecture-level masking is  hardware-dependent portion whereas architecture-level masking is software-dependent. Then AVF captures both, while their PVF is claimed to capture only the latter. “Therefore,  PVF  is  impacted  only  by changes  to  the  binary  or  to  input  data  and  not  by changes in hardware.” That’s it. It does not really say about how to statically estimate the PVF without actually running the program.

But this paper is important in that it establishes the needs for our static estimation techniques.

The architectural vulnerability factor (AVF) of a hardware structure is the probability that a fault in the structure will affect the output of a program. AVF captures both microarchitectural and architectural fault masking effects; therefore, AVF measurements cannot generate insight into the vulnerability of software independent of hardware. To evaluate the behavior of software in the presence of hardware faults, we must isolate the software-dependent (architecture-level masking) portion of AVF from the hardware-dependent (microarchitecture-level masking) portion, providing a quantitative basis to make reliability decisions about software independent of hardware. In this work, we demonstrate that the new program vulnerability factor (PVF) metric provides such a basis: PVF captures the architecture-level fault masking inherent in a program, allowing software designers to make quantitative statements about a program’s tolerance to soft errors. PVF can also explain the AVF behavior of a program when executed on hardware; PVF captures the workload-driven changes in AVF for all structures. Finally, we demonstrate two practical uses for PVF: choosing algorithms and compiler optimizations to reduce a program’s failure rate.

by Sridharan, V.;   Kaeli, D.R.;
Dept. of Electr. & Comput. Eng., Northeastern Univ., Boston, MA

This paper appears in: High Performance Computer Architecture, 2009. HPCA 2009. IEEE 15th International Symposium on

via IEEE Xplore – Eliminating microarchitectural dependency from Architectural Vulnerability.

Categories: Review Tags: ,

Create a menu for private pages and posts in WordPress | ActiveCodeline

September 14th, 2010 Comments off

A feature to implement. We want to have member-only items in the top menu line. I think this is a fantastic idea. We’ll do this later..


Create a menu for private pages and posts in WordPress

Posted by branko in General | 14 Comments

Recently I was working on a project that required a members menu on sidebar. Idea was to mark some pages and posts in WordPress as a private ones. All those marked as private are not to be accessible to all others, unregistered users, or even some registered that do not belong to some assigned role. WordPress default behavior for posts and pages is not to show up on menu if you are not registered user, which is good. However, another WordPress default behavior is to show only private posts on sidebar menu while logged in. Meaning that pages marked as private do not show up on the menu when logged in. This is not so good. I needed a solution that will list private pages on my menu as well. After few minutes of unsuccessful Google search, i decided to write my own solution. It really wasn’t that difficult. It all came down to two existing WordPress functions, current_user_can(‘some_role’) and $wpdb->get_results($some_query).

/*show pages and post mixed on menu
$menu_type = post ->show posts only
$menu_type = page ->show pages only


if(current_user_can($user_role)) {

global $wpdb;
$html = null;

if($menu_type != 'all') {
$menu_query = "post_status='private' AND post_type='". $menu_type ."'";

else if($menu_type == 'all') {
$menu_query = "post_status='private'";

$query = "SELECT * FROM $wpdb->posts WHERE ". $menu_query;
$pages = $wpdb->get_results($query);

$html .= '


return $html;


else {

$html = '

We are sorry, but only '. $user_role .' role user can access this area

# return $html;
return false;

via Create a menu for private pages and posts in WordPress | ActiveCodeline.

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Lab homepage open!

September 13th, 2010 1 comment

Thanks to many people who have contributed to this homepage, with ideas/suggestion or actual work.
Also feel free to give any new suggestions you may have about this homepage. 🙂

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Graduate Positions Available (Master, Ph.D., Post-doc)

September 9th, 2010 Comments off

We are actively seeking motivated graduate students to join the very creative team.

  • Research Areas
    • Embedded system architecture
    • Microarchitecture evaluation and optimization
    • Compiler optimization (focus on backend)
    • Multi-core and low-power compilation
    • General-purpose GPU computing (such as CUDA)
    • Neural systems engineering
  • Stipend: UNIST fellowship plus Project salary (maximum allowed by the school)
  • We regularly collaborate with top university labs (SNU) on cutting-edge research
  • Other benefits include
    • Full international travel grant on conference paper
    • State-of-the-art research facilities
    • On-campus dormitory and ideal research environment

Contact us if interested.

Categories: News Tags:

Seminar notice

September 7th, 2010 Comments off

Sep. 8, Introduction to Intellectual Property and patent attorney
Speaker: Yongjoon Jeon, Taebaek Patent & Law Firm
Time and Place: 16:00-17:00, E104

Oct. 27, Engineers, Dream and Dream Big!
Speaker: Prof. Jongwon Kim, SNU
Time and Place: 16:00-17:00, E104

Categories: News Tags:

HTM (Hierarchical Temporal Memory)

September 2nd, 2010 Comments off

HTM(Hierarchical Temporal Memory) : Not programmed & not different algorithms for different problem.

1) Discover cause

– Find relationships at inputs.

– Possible cause is called “belief”.

2) Infer causes of novel input

– Inference : Similar to pattern recognition

– Ambiguous -> Flat.

– HTMs handle novel input both during inference & training

3) Make predictions

– Each node store sequences of patterns

+ current input -> Predict what would happen next.

4) Direct behavior : Interact with world.

How do HTMs discover and infer causes?

Why is a hierarchy important?

1) Shared representations lead to generalization and storage efficiency.

2) The hierarchy of HTM matches the spatial and temporal hierarchy of the real world.

3) Belief propagation ensures all nodes quickly reach the best mutually compatible beliefs.

– Belief propagation calculates the marginal distribution for

each unobserved node, conditional on any observed nodes.

4) Hierarchical representation affords mechanism for attention

How does each node discover and infer causes?

Assigning causes.

Most common sequence of pattern are assigned.

Assigned causes are used for prediction, behavior etc.

Why is time necessary to learn?

•Pooling(many-one)  method

– Overlap

Several images of watermelons are overlapped in one picture

Learning of sequence : HTM uses this way.

4 pictures are stored sequentially

– Reference

Hierarchical Temporal Memory – Concepts, Theory, and Terminology by Jeff Hawkins and Dileep George, Numenta Inc.