Profile cover photo
Profile photo
Frédéric Hannes
Computer Scientist
Computer Scientist

Frédéric's posts

Post has attachment

Post has shared content
If it runs fast on RPi 2, it will run fast in the cloud!

Force your programmers to develop on Raspberry Pi 2!!!!

Problem: On highend notebooks, everthing appears to run fast. But later in the cloud, processors suffering under task switching between VMs and thousands of processes, cache misses dramatically increase, letting processor performance and I/O drop dramatically to just 1/100-1/1000 of what you see on your core i7 developer machine.

Here some suggestions:

- Using "column-store" databases: Speed improvement 4-15. See pioneer MonetDB.
- Using "append-only" databases: Speed improvement 10-100, allowing easy clustering, syncing. Only "append-only database engines" can scale! See #MVCC, Symas Lightning MDB #LMDB, ,
- Using "invisible joins": Speed improvement 4-100. - Using Bloom filters, Bloom joins: Speed improvement 3-70. See MySQL cluster
- Optimizing for 1st level cache (only possible with C): Speed improvement 3-10, heavily depending on algorithms.
- Using RPi 2 cluster: Speed improvement: 0-n, heavily depending on algorithms.
- Multicore (RPi 2 now has 4 cores!) programming: Speed improvement 2-3, SDRAM I/O is the bottleneck.
- Using mmap(): Speed improvement 2-3, since writing doesn't block memory reading, heavily depends on algorithms, CPU cores. ,
- Doing your own memory allocation / management, also bypassing Linux file I/O caching: Speed improvement 8-50, heavily depending on algorithms.
- Using F2FS "append only", "flash friendly" file system: Speed improvement 1-20, built to heavily reduce writes.
- Using ASYNC I/O, generators, iterators: Speed improvement - negative, but latency times dramatically decreases as well as memory/buffer consumption.
- Using Van Emde Boas Tree for huge databases: Speed improvement 2-1000, since inserts, updates, deletes go with O(log(log(N)))!!! Also allowing heavy reduction of writes to disk/flash. See Skip List databases, e.g. #SkipDB
- Using small integers only (working with prediction models, based on just 256 price categories only) for #OLAP: Speed improvement 50-10000, in combination with #columnar stores and in-memory compression.
- Use SanDisk microSDHC Extreme 32GB (SDSDQXL-032G-GA4A) only. For some unknown reason it's the only card on the market without any flaws, suited for high, sustained write I/O also!

A $35 RPi 2 typically reaches half speed of an Intel® NUC. Being programmed smart, carefully choosing right algorithms (typically only available with C/C++ programming language), it blasts a $100,000 12 Core XEON INTEL machine, so my experience. Porting then optimized C/C++ code onto cloud machines, finally can reduce hardware costs for your cloud by a factor of 8-100 at even much higher peak performance.

See e.g. Netflix, serving 20,000-30,000 customer video streams on a single, highly optimized FreeBSD 10 machine running NginX http server:

Also see performance comparison of CMS systems:

Best C++ CMS so far:

So, much to rethink for you!

Have fun!

Post has attachment

Post has shared content
This looks pretty neat! #raspberrypi  
We first saw Pi-based #polargraph +gocupi a few weeks ago; now it's on Kickstarter, for the benefit of all those who, as they put it, have a need to robotically draw images on any vertical surface.

Post has attachment

Post has shared content
Delphi comes in at 27 =/
Top 10 Programming Languages in 2014
Looking to learn a new web or embedded programming language? See graph below for trending or most looked for languages by employers.

The graph is weighted and combined by Computational journalist Nick Diakopoulos and IEEE Spectrum with 12 metrics from popular sources such as IEEE Xplore, Google, and GitHub. 

See all metrics and source here:


Post has attachment
Steam Summer Sale is rumored to begin today :O #steam #summersale  
Animated Photo

Post has shared content
Troubled by the privacy implications of Google Glass, Berlin artist Julian Oliver has written a program to detect and disconnect Glass headsets, designed to be run on a single-board computer such as a Raspberry Pi with a USB network antenna.

+Kingsoft Office The "share on Facebook" message when I try to close Kingsoft Writer is getting a tadbit annoying after 5 times. Especially considering that I don't own a Facebook account. Though I appreciate the quality free software, it might be a good idea to limit said popup to a single time.

Post has shared content
Dr. Neil deGrasse Tyson visited with Goddard's Space Flight Center Director Chris Scolese and the James Webb Space Telescope team at Goddard in Greenbelt, Md. on June 3, 2014. Tyson spoke to the team and was able to see the giant vacuum test chamber that now holds the heart of the telescope, the Integrated Science Instrument Module. 
Wait while more posts are being loaded