TL-WR841ND + OpenWRT: Success!

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My fiancée’s TP-Link TL-WR841ND (v9) router was systematically crashing when under heavy load, especially with Torrent. It was only possible to return the router to operation by power cycling it. I had tried to update its firmware with the newest version avalaible from TP-Link’s website. Nonetheless, it was not enough to solve the presented issue. In order to avoid launching this router through the 4th floor window, as last resort I tried to reflash it with OpenWRT. Here is the wiki page dedicated to this cheap router: As far as I can tell its been a success! The router […]

Fixing Nvidia + Bumblebee + Dell L502X error in Ubuntu 16.04

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For some weird reason the Ubuntu 16.04 Bumblebee’s default version was not being able to switch on/off my discrete video card NVIDIA Corporation GF108M [GeForce GT 540M]. I was getting the following error: $ optirun glxgears [ 7224.163607] [ERROR]Cannot access secondary GPU – error: [XORG] (EE) [ 7224.163722] [ERROR]Aborting because fallback start is disabled. I was able to solve the aforementioned issue in this way: 1) Adding the repository with fresh bumbleblee packages: $ sudo add-apt-repository ppa:bumblebee/testing 2) Updating the repositories and upgrade bumblebee: $ sudo apt-get update; sudo apt-get upgrade 3) Adjusting /etc/bumblebee/bumblebee.conf file: 4) Adjusting the /etc/bumblebee/xorg.conf-nvidia , […]

Fixing skype on Ubuntu 16.04

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For some weird reason my skype doesn’t open normally within Ubuntu 16.04 since it miss a required library, throwing on my face the error below: $ skype skype: error while loading shared libraries: cannot open shared object file: No such file or directory For a final solution, do: Edit the file /etc/, as root: $ sudo gedit /etc/ Add the following line to this file, save and close it: /usr/lib/i386-linux-gnu/mesa/ Then, to finish it, update your systems libraries, as root: $ sudo ldconfig And that’s it, your skype should open without hassle now. References [1] –

Thoughts after a whole day using Leap 42.1

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This a copy of the message that I tried to share with openSUSE user mail list ( but I’ve got blocked :/ I’m writing this e-mail to share my experiences after a whole day using openSUSE Leap 42.1. The installation was pretty easy and worked ok. IMHO, the boot screen is awful. But it’s a taste thing, so nevermind. Everything started to go down the hill after logging into KDE. Unfortunately, Plasma 5 is really broken, the desktop environment is so unstable that I’ve missed the panel, the krunner and/or, kwin multiple times. Working with two displays (multihead) was kind […]

Building and using an encrypted container stored in a remote host (encfs+sshfs)

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Those lines below are my notes to mount an remote folder through ssh, using sshfs [1] and building an encrypted container with encfs [2]. I’ll not explain in details how to install sshfs and encfs ’cause it dependes whether linux distribution or unix-like bsd flavor you’re running, furthermore, there are tons of documents on web convering these topics. IMHO, this is a great solution to easily store securely your files in any remote host (cloud) that you have access through ssh, using well known common unix tools. 1) Mount remote filesystem through ssh: sshfs user@host:/full/path/dir/ /full/path/mount_point It’s important to say […]

Be careful with Intel turbo boost! It can screw your benchmarking! And run slower when dealing with parallel programs!

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I wrote several months ago a little application called (I’ll open the code soon…) which calculates the active, reactive and also the apparent power in machine terminal’s over the time domain, for electromagnetic transients analysis. The files that this program have to crunch often have 1.E6 lines or more. Due to those large files this application was taking long time to finish it’s calculations 1h-3h, hence I started to transcript it into a parallel paradigm using python as well. The problem begins when I tried to benchmark the parallel version and compare with the single threaded one. The single […]

openSUSE Science e mpmath

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Para ficar registrado! Essa semana, quando estava implementado o cálculo dos parâmetros tranversais e longitudinais de linhas de transmissão para a disciplina Sobretensões Transitórias, precisei de uma biblioteca para usar com python que tivesse já disponíveis as funções de Bessel para números complexos. Achei a biblioteca numérica de precisão arbitrária mpmath [1] [2], inclusive listei no Python Numeric Cook List, a qual continha as funções necessárias, mas infelizmente não estava disponível nos repositórios oficiais do openSUSE. Depois de uma pesquisada encontrei o repositório extra-oficial openSUSE Science voltado para pacotes científicos. Página do OBS. Então, para adicionar o repositório, como root: […]