Over at an online publication called AI Game Dev, there is an elucidating post on how to do multithreading of game AI code (posted in June 2007). Basically, the conclusion is that most of the CPU time in an AI system is spent doing collision detection, path finding, and animation. This focus of time in a few domain-given hot spots turns the problem of parallelizing the AI into one of parallelizing some core supporting algorithms, rather than trying to parallelize the actual decision making itself. The key to achieving this is to make the decision-making part able to work asynchronously with the other algorithms, which is not trivial but still much easier than threading the decision making itself. The threading of the most time-consuming parts turns into classic algorithm parallelization, which is more familiar and easier to do than threading general-purpose large code bases. A good read, basically, that taught me some more about parallelization in the games world.
Wayne Wolf on “The Good News and the Bad News” of Embedded Multiprocessing
In a column called The Good News and the Bad News in IEEE Computer magazine (November 2007 issue), Prof. Wayne Wolf at Georgia Tech (and a regular columnist on embedded systems for Computer magazine) talks about the impact of multiprocessing systems (multicore, multichip) on embedded systems. In general, his tone is much more optimistic and upbeat than most pundits.
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SCDsource: Reality Check on Virtual Prototypes
Bill Murray of the “New Media Outlet” SCDsource has published one of the best articles that I have seen on the use of software simulators and virtual prototypes in industry. The examples in the article run from low-level code run on very accurate simulators all the way to very fast virtual systems that are used instead of actual hardware to train NASA operators. The article covers the end-user perspective and is not particularly oriented towards a particular vendor. It offers some nice insights into the expected and unexpected benefits that various companies have obtained from using simulators of various kinds. As well as some glimpses into the underlying technologies they have chosen, developed, and adapted.
Highly recommended.
Book Review: Intel’s Multicore Programming Book
The book “Multicore Programming – Increasing Performance through Software Multithreading” by Shameem Akhter and Jason Roberts is part of a series of books put out by Intel in their multicore software push. In case you have not noticed, Intel has a huge market push currently where they give seminars, publish articles and books, and give curricula to universities in order to get more parallel software in place. I read this book recently, and here is a short review.
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Mark Nelson’s Multicore Non-Panic and Embedded Systems
Via thinkingparallel.com I just found an interesting article from last Summer, about the actual non-imminence of the end of the computing world as we know it due to multicore. Written by Mark Nelson, the article makes some relevant and mostly correct claims, as long as we keep to the desktop land that he knows best. So here is a look at these claims in the context of embedded systems.
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When Multicore makes Things Simpler, like IMA
Most of the time when talking about the impact of multicore processing on software, we complain that it makes the software more complicated because it has to cope with the additional complexities of parallelism. There are some cases, however, when moving to multicore hardware allows a software structure to be simplified. The case of Integrated Modular Avionics (IMA) and the honestly idiotic design of the ARINC 653 standard is one such case.
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The Register reporting from SC’07
The Register has a pretty good report from the Supercomputing (SC) 2007 conference. Quite knowledgeable, and mostly about the thorny issue of programming massively parallel fairly homogeneous machines likes GPUs and floating-point accelerators. Of course, their commentary has to be commented on. Read on for more.
Off-Topic: Car Sizes and Prizes
The car market is pretty fascinating in many ways. Going out actually buying a car quite recently, I was given cause to reflect on prize vs actual size. The non-linear prize increase you have to pay to get to a slightly bigger car from whatever point you are at is interesting. And the fact that a “very small” car is just above four meters long, while a “pretty large” car is at around five meters. How can a few centimeters actually matter that much?
Intel ARK
Intel has a really neat tool on their homepage: the Intel ARK — Automated Relational Knowledgebase. It is a horrible name for a brilliant tool: it lets you search for processor names, codenames, chipsets, and jump around in a database of processor variants, compatible chipsets, feature lists, and more. Not that I care particularly about Intel chips, but the tool is something everyone selling silicon devices should copy. Being able to quickly figure out just what is inside a certain device (and what is not), and finding related devices and compatible chips is just brilliant for curious people, customers, and supporting services.
Please, everybody else?
Øredev 2007
Just like in 2006, I went to the Øredev conference in Malmö and presented a workshop using Virtutech Simics. This year, I worked with Jonas Svennebring from Freescale and we created a workshop around parallelizing network processing software for running on a multicore Freescale processor. The workshop went reasonably well, and the participants definitely learned something about what we trying to get across, even though we did not have much time to actualy complete the programming assignments.
Off-topic: Open Command Prompt Here on Vista
I just found out that my favorite Windows XP PowerToy is built into Windows Vista. To get to a command-prompt located in any folder directly from the Explorer, follow the instructions found at a Microsoft MSDN blog: Tim Sneath : Windows Vista Secret #1: Open Command Prompt Here. Very useful. But why not make it more obvious than “press shift while right-clicking?”.
Virtualization and Linux on a DSP Processor
A small tidbit that I found interesting due to the targeted platform. LinuxDevices reports that the VirtualLogix VLX-NI virtualization layer that used to run only on x86 platforms now also run on TI DSPs in the C64+ series. Basically, you put their virtualization layer on the DSP, and you can then on the same core run both a Linux kernel and a DSP/BIOS kernel. Thus supporting traditional DSP development and Linux-style development on the same core.
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Homogeneous and Heterogeneous Multicore vs Programmers
An old colleague just sent me an email bringing up a discussion we had last year, where he was a strong proponent for the homogeneous model of a multiprocessor. The root of that discussion was the difference between the Xbox 360 and Playstation 3 processors. The Xbox 360 has a three-core, two-threads-per-core homogeneous PowerPC main processor called the Xenon (plus a graphics processor, obviously), while the PS3 has a Cell processor with a single two-threaded PowerPC core and seven SPEs, Synergistic Processing Elements (basically DSP-like SIMD machines).
In the game business, it is clear that the Xenon CPU is considered easier to code for. This means that even though the Cell processor clearly has higher theoretical raw performance, in practical the two machines are about equal in power since it is harder to make use of the Cell. Which seems to be a fact.
So here, homogeneous systems do appear to have it easier among programmers. However, I do not believe that that extends to all systems, all the time, everywhere.
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Valve Source Engine Multicore Port (presentation comment)
Game engine development company Valve has a nice presentation up on their website about how they attacked multithreading. It is a nice example of how to solve multicore programming for a particular domain by the classic layered approach.
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Off-Topic: Vista Refuses Aero for Java
Vista just gave me an interesting error message: running a serious Java program required it to turn off the Aero interface. Interesting. What can Java have done to deserve that?