continuation from "Fox hole", "I wonder…", and "且如是言"
The SVC in the sklearn.svm sub-module claims to use “a squared l2 penalty”. However, the mathematical formulation in the user guide describes an L1 penalty term. Unless I have misunderstood the writing, there must be an error among the two.
Since the implementation claims to use the libsvm, which has similar documentation with linear slack terms, I am assuming the SVC is actually L1 instead of L2 as suggested by the API documentation.
When writing notes for research, it is desirable to have link that can open up citation management software with selected references so that we can easily access our personal entries on the citations.
This can be achieved by using the Zutilo add-on. It provides a menu item “Copy selected item links”. The link is in the form of zotero://select/library/items/XXXXXXXX. It is possible to configure the “mime type” for this protocol so it can be opened by xdg-open or a web browser.
IPMI is a very very powerful tool for system administrators, especially those telecommuting ones. It’s serial over LAN (SOL) support eliminates the need to personally sit in front of a server to do any pre-network operations, including reconfiguring the BIOS settings. However, it does require (A) an additional IP address to access the IPMI network interface from the Internet; or, when no additional IP can be allocated, (B) the access to a second server on the same LAN (not necessarily with administrator privilege). When either (A) or (B) is available, you can theoretically do anything remotely including fresh installation of an operation system (starting, for example, with a network boot and/or a remote drive).
Unfortunately, one of my recent situation allowed neither (A) nor (B). So, the first installation had no option but to be done by on-site personnel. But, once a networked system was up and running with a working grub boot manager, I could remotely install a new system on an unused (or a large enough swap) partition and test it out with the “boot once” support of grub. On a Debian based system with grub-2, this involves
However, in most cases, you are bound to make some mistakes in the new system and fail to recover network contact to the server until an on-site person can hit the reset button of the machine for you.
Lucky for me, the BMC of the IPMI on the server did have a working watchdog timer. Therefore, I could setup the timer with enough time and start it before rebooting the machine. That way, if the new system worked, I could login to the server through the Internet and stopped the timer. But, if the new system got stuck, the watchdog would do a hard reset on the machine after the time ran out and returned to the original working system… no more waiting for on-site personnel. The actual command I used to setup the timer is bmc-watchdog from freeipmi:
One can consult the man page for the meaning of these options. Simply, this sets up 15 minutes on the timer for a hard reset, which can be checked with
started with
and stopped with
(While, theoretically, one can achieve the same result with ipmitool, it did not work for me on the specific system.)
It has been for a few occasions that I find my self wanting to port my GUI programs (most of which were written with gtkmm) to other platforms for the enjoyment of my friends. However, while most GUI toolkits claim to be portable to all platforms (Linux, Windows, and Mac), they generally require installation of multiple shared libraries by the users.
This is a major show stopper for most of my friends and is sufficient to kill any interest in them on the first mention. Therefore, the only viable mean is for me to make and send them statically-linked, monolithic executables that they can happily click on to start the shows. (They generally don’t mind waiting a few minutes to download a bloated binary, as long as it remains a single step.)
My recent survey of the GUI library landscape brought my attention to GLUT. While it still requires installation on Windows, I can easily find static versions of FreeGLUT library for MingW that can be used to cross-compile, on Linux, statically-linked executables that can run independently on Windows. Furthermore, the GLUT framework, which, according to this, “is installed with every install of Mac OS X”.
However, GLUT library only provides facilities for managing windows and handling user inputs. It is by no means a GUI toolkit and you will have to draw all user-interactive elements by yourself (in OpenGL). I do find a GUI library, GLUI, that is built on and should be as portable as GLUT. However, after porting a couple programs to GLUI, I failed to find it enjoyable for me to break up the C++-elegant logic of gtkmm and redo my work in a less polished API.
What follows is the birth of gltk, it is an implementation of the gtkmm API on GLUT. I actually started with adding the libsigc++‘s signal-slot API to GLUI since the original callback mechanism only supported single static callback function and I needed more flexibility to port my programs. But, the hack soon proliferated into the entire source tree, and I decided it would be much more enjoyable for me to start something entirely from scratch.
After a somewhat persisting part-time effort that lasted more than a month, I have just made the first release of the library. It’s usable for a simple application that only needs some buttons, checkboxes, sliders, single line text labels or entries to control calculations. For myself, this represent over 80% of the applications that I would have considered porting. I am feeling pretty happy about it and I hope some others will also find it useful.
Project Homepage: http://gltk.ccdw.org/
I just released arg as a standalone library under LGPL. It’s a command-line parser for C++ programs. The aim is to keep the programming effort in adding command-line processing to C++ programs at a minimum. There are several considerations in this direction:
The simple example as given on the arg homepage,
#include <arg.hh>
#include <iostream>
int main(int argc, char ** argv)
{
arg::Parser p;
int n;
p.add_opt(‘n’).stow(n);
p.parse(argc, argv);
std::cout << n << ‘n’;
return 0;
}
should be very close to the minimum as far as 1. goes.
Programming is for a programmer to describe what he wants the computer to do. Per point 2., he should not be asked to provide the same information multiple times. (Well, maybe except in situations where multiple confirmations are required: “Launch the missile. Please have the missile launched. Yes, I really want you to launch the missile! Launch the *&^%$ missile!!!”; Computer: “Aborted on Error: missile != *&^%$ missile”.)
When working on an item, e.g., adding a new command-line option, the programmer won’t be asked to go to multiple places in the codes if 3. is observed. While common and frequent usages should be supported and simplified in the library, new and novel applications will ask for 4. Finally, some rare, special, and/or tricky applications will demand 5. in the arsenal.
This is a very neat way to add math to a web page. It’s as easy to use as typing in TeX and much portable than the right way of doing such things.
There is an old Chinese saying: “Doing a good job requires a good tool”. Here is a very good tool for my trade.
