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Glenn K. Lockwood
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See ya Google+. I'll be on twitter @glennklockwood.
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I got an FPGA for Christmas and decided to start educating myself on how to use them. It didn't take long to realize that they are not nearly as magical as some HPC pundits claim they are, so I wrote this up to illustrate where FPGA-based acceleration of HPC codes may really wind up in the next few years.
Are FPGAs the answer to HPC's woes?
Are FPGAs the answer to HPC's woes?
glennklockwood.blogspot.com
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A little different from my usual posts--a dissection of the I/O subsystem on a desktop system and all of the neat widgets that never see the light of day in the data center.
Understanding I/O on the Mid-2017 iMac
Understanding I/O on the Mid-2017 iMac
glennklockwood.blogspot.com
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I couldn't help but write a bit of a rebuttal to a recently posted blog post that trashes tape in favor of disk-based object store. I get that it's fun to beat up on tape as an ancient storage technology, but it's still alive and kicking for a few very good reasons.
A less-biased look at tape versus disks
A less-biased look at tape versus disks
glennklockwood.blogspot.com
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Related to my burst buffer blog post, I also recently updated the nonvolatile memory technologies page I had on my website. It's very hardware-focused, but it might be of interest to those who would like to learn the basics of how SSDs are built and operate, and where SSD technology is going.
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I've been sitting on this post for over six months, but after a call with some colleagues of mine who wanted to know more about burst buffers, I was reminded that there aren't a lot of great resources out there that have an up-to-date view of where the burst buffer ecosystem stands today.

To do my part and share the knowledge, I put a bow in this post and present a breakdown of what burst buffers exist (or will exist) in terms of hardware and software.
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This article stops short of saying what I expected it to--don't write multi-threaded programs by hand if you can use OpenMP.

The biggest reason is not really acknowledged in this article--OpenMP is a lot more than compiler directives; it's also a performance runtime. The developers of OpenMP runtimes have put monumental effort into optimizing the inner workings of the thread scheduling to be performance portable and scalable. Programming threads "by hand" throws all of this out the window and leaves you, the programmer, to reinvent the wheel.

Take for example thread binding--with pthreads, you have to bind threads to cores by hand, and without a lot of effort, your choice of core binding will not be performance portable to other processors. With OpenMP, you simply set a single environment variable, and your threads are bound according to the automatically discovered processor topology.

Other examples exist for thread scheduling (e.g., blocking loops), thread creation/destruction (e.g., active thread pools), and just about every other non-trivial aspect of multithreaded programming. So, unless you enjoy wasting time programming that which has already been optimized, don't program threads by hand.
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My colleagues at SDSC are looking for someone who wants to get his or her hands dirty supporting their Gordon and Comet systems. This is a fantastic opportunity to get into the HPC industry and exactly how I got my start, and it comes with a lot of opportunities to pursue research, industrial collaboration, and involvement in the larger scientific computing community.

SDSC will be at SC'16, as will I, and I'm happy to connect anyone who's interested in this position with the right people over at SDSC. Let me know!
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We're building some of the biggest and fastest supercomputers in the world, and we're looking for people to help us design them. NERSC and LBNL has great people, great technology, and a great view, so please get in touch with me if you or anyone you know is interested.

Job description is here: https://lbl.taleo.net/careersection/2/jobdetail.ftl?lang=en&job=83027
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I've had this blog post half written for a number of months now. Figure I should just publish it so that I can always remember what all the important IOR flags are.
Basics of I/O Benchmarking
Basics of I/O Benchmarking
glennklockwood.blogspot.com
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