Tag: non GIS

Ciao, Xiaomi, ciao.

Posted by – Monday 2016-08-08

About a year ago, the Chinese smartphone maker Xiaomi was burgeoning and among the top 5 sellers. In last months Xiaomi has lost ground to its competitors, and currently is not among them.

As an angry Xiaomi ex-customer, it makes me feel a bit happy. I think that Xiaomi deserves such fate, as well as another much worser.

A Xiaomi show

Why I bought, about two years ago, a Xiaomi RedMi 1 smartphone? For me, the selling point was the operating system. Xiaomi smartphones feature MIUI OS, a very polished version of the ubiquitous Android OS.

At the beginning it looked promising, but finished badly.


WordPress: a recipe for switching from Apache to Nginx.

Posted by – Monday 2016-05-23

This blog runs on a bunch of software items, among them an instance of the WordPress content management system and a web server. For years I have trusted on the Apache HTTP server, despite I never liked it. Recently I switched to Nginx, a web server that is gaining a lot of traction, particularly among the busiest web sites [1, 2].

Why did I do this switch? For some reason unknown to me, some weeks ago Apache’s appetite for RAM memory went through the roof. None of the solutions I tested worked, including an update from version 2.2 to 2.4. Thus, I had a blog that was unusable: almost every request raised a HTTP 500 error. The following data provides some context: this blog is a low traffic one – it serves an average of 70 pages per day – and it is hosted on an inexpensive VPS that has 512 MB of RAM memory.

The solution I took was switching to Nginx, and it worked.

LEMP: Linux + Nginx + MySQL + PHP

This post is a quick-and-dirty recipe for switching an existing WordPress blog from the Apache web server to Nginx in a machine running a Debian 7 operating system. There is no original research: the instructions given here are taken from several web pages about Nginx, PHP and WordPress and put together here; and it is likely that there is room for improvement.


Exporting MS Access databases to SQLite.

Posted by – Saturday 2015-07-25

Sometimes you are given a database in MS Access (MDB) format. If your operating system is MS Windows and you have a MS Access license, working with this database should not be a issue.

If your operating system is Linux, the odds of working smoothly with such database are not good. The usual recipe for opening a MS Accesss database – actually, a MDB file – in a Linux machine is using LibreOffice Base plus the appropriate database driver. Usually this recipe will not work at the first attempt – and neither after many.

MS Access to SQLite

The alternative explored in this post is exporting the database from MS Access to SQLite. Both database technologies have in common the feature of being serverless. The output of this export process is a SQLite database which, like a MS Access database, is stored in a single file.


Anonymous, you are very wrong.

Posted by – Sunday 2012-01-22

After Megaupload.com shutdown, Anonymous countered with DDoS attacks against websites such the USA’s Department of Justice or the MPAA.

Anonymous, you are very wrong. Do you who really know is Megaupload’s founder, Kim Schmitz (alias Kim ‘Dotcom’)?

Kim Schmitz, Megaupload's CEO

Kim Schmitz
picture taken from elmundo.es

According to the Wikipedia:

In 1998, Schmitz was sentenced to a probationary sentence of two years for computer fraud and handling stolen goods. According to a report by News & Record, he had traded stolen calling card numbers he bought from hackers in the United States.


In 2001, Schmitz purchased $375,000 worth of shares of the nearly bankrupt company LetsBuyIt.com and subsequently announced his intention to invest EUR 50 million in the company. Unknown to others, Schmitz did not have the funds available to invest, although the announcement caused the share value of LetsBuyIt.com to jump by nearly 300%. Schmitz quickly sold the shares and profited $1.5 million as a result.

Schmitz had also arranged and obtained an unsecured loan of EUR 280,000 from Monkey AG, a company for which Schmitz had served as Chairman of the Board. The funds were to be paid to Kimvestor AG. As a result, both Monkey and Kimvestor went bankrupt. Schmitz expressed remorse, stating that he had been “dazzled” and had not recognized that he would be unable to repay the loans.

In January 2002, Schmitz was arrested in Bangkok, Thailand, deported to Germany, and sentenced to a probationary sentence of one year and eight months, and a EUR 100,000 fine, the largest insider-trading case in Germany at the time. Schmitz also pleaded guilty to embezzlement in November 2003 and received a two-year probation sentence.

Wikipedia: Kim Dotcom

The (now) defunct Megaupload.com has nothing to see with the Wikipedia or freedom speech in general. By supporting Megaupload.com you are actually disservicing the cause. I did not join last Wednesday blackout to support Kim Schmitz or other crooks who make tons of money by using other’s work.

I do hate the MPAA, the Spanish Sociedad General de Autores y Editores and the like. But what Kim Schmitz does is not the way to follow.

Profiling application LLC cache misses under Linux using Perf Events.

Posted by – Wednesday 2011-11-30

In this post we will see how to do some profiling under Ubuntu Linux using Perf Events, present in the kernel since version 2.6.31 [1, 2]. In particular, we will estimate the rate of Last Level Cache (LLC) misses that a Java application has.

There are GIS applications that are computing power hungry; among them applications processing LiDAR data are an example, because the volume of the input data is usually huge. The efficient usage of the processor caches can boost execution time. Given the high penalty processor cache misses have, identifying application areas causing too much cache misses is very important.

1. Installation of Perf Events

Fortunately, Ubuntu Linux offers Perf Events (PE) in the form of binary packages. By using the command apt-get, installation is straighforward:

$ sudo apt-get install linux-tools-common linux-tools-2.6.38-13

Two notes about installation. First, before attempting installation check that the kernel you are using is recent enough: Perf Events [note 1] is available since Linux version 2.6.31. Second, install a version of the package linux-tools matching your kernel version.