Friday, 11 April 2014

PCB for ADC board for ATLAS TileCal Prometeo system

Five PCBs for the ADC boards for the ATLAS TileCal Prometeo system manufactured in Johannesburg. The Prometeo system is designed for the upgrade. The first version will be used for the certification of the hybrid demonstrator.

Two PCBs have been sent to be populated. We are aiming at sending the boards to Europe by the end of the month.



Thursday, 10 April 2014

Announcement of Kruger 2014

WORKSHOP ON DISCOVERY PHYSICS AT THE LHC

KRUGER-2014

December 1 - 6, 2014

Protea Hotel Kruger Gate

Portia Shabangu Road, Skukuza, Mpumulanga, South Africa
Dear Colleagues

We are pleased to announce the Third  Biennial

   "Workshop on Discovery Physics at the LHC" (KRUGER 2014)
The Workshop will be held at the 4-star Protea Hotel Kruger Gate,
just 100 meters from the  entrance to the Kruger National Park.

Please find details in the conference web page
http://www.kruger2014.tlabs.ac.za
The conference aims to promote scientific exchange of new results
and development of
novel ideas and models related to the physics of the LHC.
The following topics will be covered:
 Particle Physics,
  Heavy Ion Physics,
 Physics  after the discovery of the  Brout-Englert-Higgs boson.
Accommodation, registration, abstract submission and other practical
details can be found
on the web page. Attendance will be limited to about 100 participants
because of the number of available  rooms in the hotel.

Students are encouraged to also take part in a related workshop/school on
  ``Hot and Dense Nuclear & Astrophysical Matter - HDM2014''
which will be organized by Professor Azwinndini
Muronga (amuronga@uj.ac.za)  at the University of Mafeking
November 24 - 28, 2014.

Other related events of interest to students are:
  ``Chris Engelbrecht School in Particle Physics'',
January 12 - 21, 2015,
and the
  ``High Performance Signal and Data Processing'',
January 26 - 30, 2015.
Limited funding for South African students is available.
We look forward to seeing you all in South Africa

The organizers of KRUGER-2014:

O. Boeriu (Witwatersrand, Johannesburg)  Z. Buthelezi  (iThemba LABS)

J. Cleymans (UCT, Cape Town) (Chair)  A. S. Cornell
(NITHeP/Witwatersrand, Johannesburg)

S. H. Connell (UJ, Johannesburg)  T. Dietel     (UCT, Cape Town)

S. Frtsch    (iThemba LABS)  N. Haasbroek  (iThemba LABS) (Secretary)

A. Hamilton (UCT, Cape Town)  W. A. Horowitz (UCT, Cape Town)

S. Karataglidis (UJ, Johannesburg)  B. Mellado  (Witwatersrand, Johannesburg)

E. Sideras-Haddad  (Witwatersrand, Johannesburg)  T. Vickey
(Witwatersrand, Johannesburg)

H. Weigert   (UCT, Cape Town)  S. Yacoob    (UKZN, Durban)

The email address of the conference is kruger2014@tlabs.ac.za




Wednesday, 2 April 2014

Dual Wandboard PCI-Express Connector Complete

The Wandboard PCI-Express adpater is complete! I'm in the process of building a new kernel that supports the PCI-Express RC and Endpoint to start testing the Freescale i.MX6 Quad PCI-Express capabilities.

Here are some photos of the completed board with two Wandboards attached! In the last photo you can see our (now slightly diminished) Wandboard cluster. We are waiting for another five Wandboards to make it 40 cores but no suppliers seem to have stock at the moment...




Friday, 28 March 2014

Wandboard PCI-Express Connector PCB Photos

Today I took delivery of the first (and hopefully last if it's bug-free) version of the dual Wandboard PCI-Express adapter. I plan on having it soldered and ready for testing by early next week. Check out the photos!



Wednesday, 12 March 2014

Wandboard PCI-Express Adapter: Update

It's been a while since I last posted about the Wandboard PCI-Express adapter I have been working on... I decided to redesign the PCB to be more compact. This saves manufacturing costs and it looks better, in my opinion.

The PCB has been sent for manufacture so hopefully in a week or two I can post some photos! Shortly after that - assuming everything goes according to plan - I'll post some results for the PCI-Express performance of the Freescale i.MX6 SoC. I don't think the PCI-Express interface to the Wandboard has been tested by anyone, so hopefully it works...



Tuesday, 11 March 2014

NAS Benchmarks on ARM

The NAS Parallel Benchmarks (link) are a comprehensive suite of benchmarks to test supercomputers, maintained by NASA. They were originally based on computational fluid dynamics (in 1994) and expanded over time to cover many different problem types as well as many problem sizes; from very small problems that run in a few seconds for testing purposes, to large problems that can take hours on a supercomputer!

Since these benchmarks cover a range of problems, most interestingly a specific Embarrassingly Parallel benchmark, it is important to test their performance on ARM. Luckily the task of building the benchmark suite on ARM is straightforward. I will document it here for those who are interested. I will write about performance tweaks and compiler flags in a later post once I have had more time to experiment.


Installation (Single Processor Test)

  • Download a copy of the source code from the web site linked above. Unzip the source into a directory on your ARM system.
  • You should already have a full suite of compilers (gcc) installed on your system, as well as MPICH or other MPI library.
  • Navigate into the NPB3.3-MPI directory. Please read the README.install text document for some details. There is a short document in each benchmark directory with some details about that specific benchmark.
  • Navigate into the 'config' directory.
  • Run this command to use the template for the build: cp make.def.template make.def
  • Then run this command to use the template for the suites: cp suite.def.template suite.def
  • You now need to customize the make.def file to your system. Your modifications should be the same as mine if you are running Linux (Linaro) on ARM. Scroll through the file and adjust the lines as below:
MPIF77 = mpif77
FFLAGS = O3
MPICC = mpicc
Un-comment include ../config/make.dummy

  • Note that we uncommented the make.dummy file. This means that true MPI will not be used, and all of the benchmarks will only run with single processor as a simple test.
  • The template suite.def file is fine for this proof-of-concept.
  • Return to the root directory of NAS with ../
  • Type make suite and wait for the build to complete. If something goes wrong there may be an issue with a dependency.

Installation (Multi-Processor MPI)

To install a true MPI version, follow the steps above, except leave the make.dummy commented. You should also modify the suite.def file to suit the number of processors (processes) you would like to run.

To run a multi-processor version type:
mpirun -np 4 ./bin/ep.S.4
For a 4 processor version of EP with a size of S. Obviously the benchmark must be compiled for the correct number of processors. You need to update the command accordingly.

You can selectively compile a single test at a time. Please see the README.install file - it's really quite simple.

Thursday, 6 March 2014

Does the Fused Multiply-Add (FMA) instruction make a difference?

I discussed this originally in my Cortex-A7 FFTW benchmarks, but I am repeating it in it's own blog post for clarity as I believe it's an important thing to understand.

I noticed that when enabling the FMA capabilities of FFTW, the performance actually decreased. I thought to myself "but the ARM VFPv4 supports FMA so this should be faster that doing separate multiply and add operations..." so I did a little bit of research as to why this is the case.

In the computation of an FFT, two of the common operations are:

t0 = a + b * c
t1 = a - b * c

The way that the NEON FMA instruction works, however, is not conducive solving this. This is what happens when you use the NEON FMA instruction:

t0 = a
t0 += b * c
t1 = a
t1 -= b * c

Since ARM is a RISC architecture, the instructions are less flexible and generally take a fixed number of operands. For mathematical operations, it makes sense most of the time to use two operands. Because of this limitation, the FMA can still only take 2 operands and so it is used as shown above. Notice that we have to use up two move instructions for initially setting t0 and t1. It turns out that in this specific case it's faster to just use Multiplies and Adds:

t = b * c
t0 = a + t
t1 = a - t

All in all, the FMA version does 2 Moves, 2 FMA's. The optimal version does 1 Multiply and 2 Adds. It's a small difference, one which the compiler may or may not take note of and optimise, but when done a significant number of times it makes a difference which is what we see in the FFTW benchmarks, for example. There will be cases when this instruction does indeed make a difference, but it's important to bear in mind what's going on behind the scenes.

High Speed PCB Routing

I have been quite busy designing high-speed PCB's for my PCI-Express research. I found this video on YouTube from Texas Instruments which provides an excellent overview on high speed routing and I recommend it to anyone interested.


To reiterate the issues one usually faces when designing high speed circuit boards (from the video above):

  • Timing: the lengths of the tracks must be similar enough for the electrical signals to arrive at the receiver at the same time. ~0.6 times the speed of light is too slow!
  • Signal Integrity: The shape of the signal needs to be right when it arrives at the receiver.
  • Noise: There can be a lot of crosstalk and noise on a high speed PCB and this noise can adversely affect signals.
To 'solve' these concerns:
  • Maintain the correct impedance from the transmitter to the receiver. This is not always trivial and so this is usually the biggest problem!
  • Matched lengths minimise signal skew.
  • Leave space around the traces to minimise noise. More space makes an exponential difference.

Wednesday, 5 February 2014

Nice article on the importance of the SA-CERN program

Nicola Mawson, from ITWeb has written a nice appraisal of the importance of the role of the South Africa - CERN program and its benefits to the country.

http://www.itweb.co.za/index.php?option=com_content&view=article&id=70626:SA-reaps-CERN-rewards

SA's involvement with the Large Hadron Collider (LHC), in Switzerland, is paying dividends as the country embarks on new electronics and physics projects, and benefits from knowledge gained at the European Organisation for Nuclear Research (CERN).
Thanks to collaboration on the project – the £2.6 billion "Big Bang" particle accelerator and the globe's largest experiment – South African universities are developing technology in fast electronics, supercomputing and plastics.
The LHC at CERN led to the discovery, in 2012, of what has become accepted as the elusive Higgs boson. This discovery is anticipated to catapult physics into a new era, as it will be able to probe previously untouched areas, such as dark matter and dark energy.
Click here
The Higgs particle – or boson – is named after Peter Higgs, who was one of six authors who theorised about the existence of the particle in the 1960s. It is commonly called the "God Particle", after the title of Nobel physicist Leon Lederman's "The God Particle: If the Universe Is the Answer, What Is the Question?", according to Wikipedia.
Locally, about 70 South Africans are involved in the global project and, while the team is small in comparison to those from other countries, there are substantial benefits coming out of its involvement.
Four universities are participating in the programme: the University of the Witwatersrand (Wits), University of Cape Town (UCT), the University of Johannesburg, and the University of KwaZulu-Natal.
Tom Dietel, a lecturer at UCT, says CERN is a flagship project and is expected to spark interest in science and physics.
Bruce Mellado, an associate professor at Wits' school of physics, says the tertiary institution is involved with projects to develop fast electronics, a new form of plastic, and create a cheap alternative for high-throughput supercomputing.
Mellado explains South Africans have been given the opportunity to tap into CERN's infrastructure at very little cost to the country. He says the country has been "given the benefit of a huge facility without having to pay hundreds of billions for it".
Professor Jean Cleymans, from the UCT's physics department, explains SA's involvement – mostly with the Atlas experiment – is a national project and is not specifically linked to any university. SA is also making contributions to the Alice and Isolde projects, he says. "It's important to have a first step in there."
Cleymans says SA's involvement gives young physicists access to technology, software being developed and knowledge.
Cleymans says "far from being limited to Europe", the project is a worldwide project to contribute to advances at CERN. SA's first step happened in 1992, when it signed its first agreement of interest, he notes.
Mellado explains one of the university's initiatives – named sRod – is a faster electronics board, which will be able to process much more data at faster rates. The board, being developed through collaboration in Europe and SA, is being made in conjunction with SA's Square Kilometre Array (SKA) team.
The multibillion-rand telescope project, hosted by SA, Australia and New Zealand, will collect a staggering amount of data as it probes the universe: the data collected by the SKA in a single day would take nearly two million years to play back on an iPod.
Mellado says the prototype board should be in production locally before winter, which will be a "major milestone for SA". He explains there are increasingly large amounts of data to be analysed, but the price for the hardware is currently a "showstopper".
Being able to get university-made technology commercialised will drop the cost and allow SA's technology industry to develop further, says Mellado. "That's the key to further development."
Wits is also developing a supercomputer under its Mass Affordable Computing project, which Mellado says takes the technology from smartphones and uses it for generic applications such as telecoms and computing. This programme will also be used to aid the SKA's data processing needs. "We can proudly say that we are doing it here."
Such projects are critical to SA's science, says Mellado. "Everything now depends on data processing."
The university is also developing – in collaboration with Sasol – plastic scintillators, with a prototype due in a year or two. Mellado says this material will allow the absorption of light.
The South African consortium launched in 2008 and a few ministerial delegations have visited CERN, says Cleymans. SA's contribution is hosted by iThemba Laboratories, which is a national open laboratory, he adds.
The Department of Science and Technology is funding SA's contribution, says Cleymans, adding that CERN is the first project that has seen South African physics departments team up to collaborate.
CERN is currently temporarily offline in a bid to increase its capacity and explore unknown aspects of physics. In the meantime, South African scientists are helping analyse the data it has collected and are aiding with maintenance.
The experiment will run until 2030 and will be upgraded to 10 times its initial design specification, with the ability to collect 100 times more data.

Monday, 3 February 2014

Wits Honored to be remembered in Madiba's will

Below is a statement from the Vice-Chancellor and Principal of the University of the Witwatersrand:


Dear Colleagues

The University of the Witwatersrand is honoured and deeply appreciative to learn that it is a beneficiary of former president Nelson Mandela’s legacy, and we are indeed humbled that he chose to remember the University in his will.

Wits accepts this generous bequest from one of our most illustrious alumni and commits to using it to address the development of higher education in South Africa, for the benefit of the University and its students, but more importantly to advance and perpetuate the values that our inaugural President has bequeathed to our nation and the world.     

Madiba emphasised the need to address inequality – one of the greatest threats to our young democracy, and Wits is determined to utilise this endowment to tackle this societal peril without delay, through the provision of additional scholarships for our students.  

We understand that this endowment brings with it a tremendous responsibility, given the character and legacy of our great leader and his commitment to the transformative power of education.

Thank you, Tata, for remembering us in your will – you live on in our memory and in our lives. 

Professor Adam Habib
Vice-Chancellor and Principal
University of the Witwatersrand
3 February 2014