# CVX Annouced Version 2 (Beta)

CVX has become an indispensable tool for modeling and prototyping in various scientific disciplines, in particular where optimization play significant roles.  It provides a most intuitive modeling interface that bridges complex formulation and the underlying numerical solvers, saving the user abundant time for thinking.

Version 2 of CVX has featured extended support for commercial solvers, MOSEK and Gurobi. This is really good news for academic users, since 1) both solvers provide free licenses to academic users; and 2) both solvers are mostly more optimized than the free solvers currently bundles with CVX, namely, SDPT3 and SeDuMi. Related part of the announcement as follows:

• Academic users may utilize the CVX Professional capability at no charge.

• Users with a valid academic license for Gurobi 5.0 or later may use it with CVX without obtaining a CVX Professional license. This is because CVX is able to detect the presence of an academic Gurobi license.

• In order to use MOSEK, a CVX Professional license is required. We intend to provide such licenses at no charge, but we have not yet completed the licensing architecture. We will make an announcement once this has been completed.

In addition, mailing list support has changed into a Q&A forum (StackExchange style …) and the documentation has changed to online html version with better cross references.

# Battery Problem With Nikon Coolpix L100

Nikon Coolpix L100 is a compact Megazoom digital camera, coming with 15x optical zooming capacity and wide view angle - ideal for amateur photo-takers like me . The price is also not bad, at about \$400 Singapore dollars when I bought one in 2009. The only pitfall is with its batteries: at the outset, it simply doesn’t accept rechargeable batteries, such as the typical Ni-MH’s - even you’re not a doctrine environmentalist, it may bother you a lot whenever you have to head for stores for batteries.

In fact, Nikon has added in rechargeable support not long after this camera was released. You can follow these steps to get your L100 live well with the rechargeable:

1. Firmware Version. Press the MENU botton, and go to Set Up –> Firmware version. If the firmware is COOLPIX L100 Ver.1.0, you will need to update your firmware to V1.1. following these instructions (Coolpix L100 1.1 firmware update from Nikon website).

2. Battery Type. After the updating, one has to select Set up –> Battery type –> COOLPIX (Ni-MH) to enable this lovely feature.

Now you should be able to power your L100 with your rechargeable batteries (and also still be able to use the disposable)！

# My Picasa Albums Updated!

This includes some of my activities in the past several months!

My Albums

Stay tuned!

# Useful Tips on Running External Programs From Matlab on Linux

Most of these problems stem from bad association of Matlab’s C++ (or Fortran) libraries. The solution is often to create a soft-link and point to the corresponding system libraries. This blog article provides a very nice summary of this!

Matlab: Running External Programs

# Shapiro and Mudd …

PS： 今天presentation 把without loss of generality 说成 without loss of generosity 。。。被John 掐住好，很肿的补了句 Anyway we cannot lose it …

# A Tight Lower Bound for Finite Sum of Arctangents

Days ago we ran into a need to lower bound $\sum_{j=1}^k \pi/2 - \arctan j = \sum_{j=1}^k \arctan 1/j$.

One possibility is observe the non-negativity and continuity of the function $\arctan x$ over $j \in {\mathbb Z}_+$ and apply an integral lower bound: \begin{align*} & \sum_{j=1}^k \arctan \frac{1}{j} \newline \geq \; & \int_{1}^{k+1} \arctan 1/x \; dx = \left. x\arctan 1/x + \frac{1}{2} \ln \left(1+x^2\right) \right|_{x = 1}^{k+1} \newline = \; & \frac{1}{2}\ln \left[\left(k+1\right)^2 +1\right] + \left(k+1\right) \arctan \frac{1}{k+1} - \frac{\pi}{4} - \frac{1}{2} \ln 2 \newline \geq \; & \frac{1}{2}\ln \left[\left(k+1\right)^2 +1\right] + \left(k+1\right) \left(\frac{1}{k+1} - \frac{1}{3} \frac{1}{\left(k+1\right)^3}\right) - 1.132 \newline = \; & \frac{1}{2}\ln \left[\left(k+1\right)^2 +1\right] - 0.132 - \frac{1}{3} \frac{1}{\left(k+1\right)^2}, \end{align*} where in the third line we have retained the first two terms of series expansion for $\arctan x$ for $\left|x\right| \leq 1$. The integral approximation gives very messy terms and a somewhat loose lower bound. We can obtain a much neater one: \begin{align} \sum_{j=1}^k \arctan \frac{1}{j} \geq \log \left(k+1\right). \end{align}

I’m finished with my finals, after interrupted study and broken rest time for several days – you must pay afterwards even with unmindful procrastination on the move.

Qualification Exam is ahead within two plus weeks. It’s the time to get refreshed my mind with the concepts of circuits, Fourier transformation, registers, and bit error probability, pretty everything a typical electrical engineering graduate needs to know. Yuh… another fighting! Of course the words your professor would often spend on this issue is > make sure you pass, but not spend too much time! It’s an interesting balance a graduate student most likely always tries to strike…

Visits to this blog keep roll up, even after my absence in the past few months. I’m pleased to be noticed of the 20,000 hits by the system. I’ve decided to put reasonable amount of time in future to update this blog with more technical expositions and discussions. This would considerably improve my ability to understand technical materials, which I would need to sharpen as soon as possible.

I was just having a Christmas dinner with John and one master student. It’s pretty fun! We consumed some 1.5 bottles of red wines. And John was asking one theorem for each bottle we had for next semester, jokingly …

# CV Meeting – Frontiers in Computer Vision

Prof. Alan Yuille (UCLA) in parter with others is organizing a special workshop for exploring frontiers in vision, a good chance for researchers to pause a while and look backward and forward.

Frontiers in Computer Vision

From the cyber-discussion being fired there, some interesting disagreements amongst these top vision researchers are already significant: conservatism versus radicalism, and pragmatism versus idealism. For a research community as ambitious and diverse and young as vision, nevertheless, consensus rarely occurs and ideological debates prevail – it is not surprising; in fact, this signals an active research field in my opinion. But my humble mind is really seeking some fuels the workshop could potentially generate for these topics:

1. Object recognition
2. Culture of scholarship in vision

The former has been central on the spot for the past 10 years with least success, while the latter has partially contributed to the dismal stagnation.