tmurray

7 ms·

1.
by tmurray 6y ago
they're not a userspace construct in any meaningful way. libutils/Thread (capital-T Thread) is a thin wrapper around pthread_t, and most Android code uses pthread_t directly. what this hit is probably a bug related to timerslack_n
2.
by tmurray 11y ago
GPUs don't have a page fault handler; when there's a page fault, it's an unrecoverable crash. Accordingly, zero-on-allocate (or potentially zero-on-free, but that makes assumptions about startup and teardown that may not be t
3.
by tmurray 11y ago
X1 is actually the 64-bit ARM CPU configuration (Cortex A53 + Cortex A57), not Denver. K1, the predecessor of X1, comes in two flavors: 32-bit 4xCortex A15 and 64-bit 2xDenver. TK1 is 32-bit, Nexus 9 is 64-bit (and is the only device I know
4.
by tmurray 12y ago
property taxes are capped in CA, so the landlord's costs are essentially fixed: http://en.wikipedia.org/wiki/California_Proposition_13_%2819...
5.
by tmurray 12y ago
I actually read IJ on a Kindle and found it significantly easier for the most part than reading it in print because of links to endnotes, which removed the requirement to keep two sets of bookmarks (if you haven't read it, some endnote
6.
by tmurray 12y ago
GPUs don't support precise exceptions. For example, you can't take a GPU program that contains a segfault, run it as a standard program (as in, not in a debug mode), and be presented with the exact instruction that generated the f
7.
by tmurray 12y ago
https://gcc.gnu.org/onlinedocs/gcc-4.7.4/gcc/Function-Attrib... and http://pasky.or.cz/dev/glibc/ifunc.c look up the target attribute and the ifunc attribute--it's basically a
8.
by tmurray 12y ago
but that's GLES 2.0, which is significantly less flexible than the kinds of GPUs we're discussing here and is not even in the same ballpark as a CPU (and almost certainly significantly less strict in terms of floating point precis
9.
by tmurray 12y ago
disclaimer: I work in this space and have done so for a while, including previously on CUDA and on Titan. GPUs for general purpose computation were never 100x faster than CPUs like people claimed in 2008 or so. They're just not. That w
10.
by tmurray 12y ago
Kayvon teaches at Carnegie Mellon now and his class slides are definitely worth reading: http://graphics.cs.cmu.edu/courses/15869/fall2014/ http://15418.courses.cs.cmu.edu/spring2014/
11.
by tmurray 12y ago
sorry, the desktop Intel SIMD ISAs are generally not something I use on a day-to-day basis, so I get them mixed up a lot. (LRBni was the last one I looked at for any serious length of time.)
12.
by tmurray 12y ago
I spent a lot of the past month improving the RenderScript (Android data-parallel compute, using C99 plus vectors) codegen to better work with the LLVM vectorizers, so I have a fair amount of experience with this exact question. The vector
13.
by tmurray 12y ago
>> 20 years of legacy, needs a reboot and major simplification pass This was attempted. It failed: http://en.wikipedia.org/wiki/OpenGL#Longs_Peak_and_OpenGL_3....
14.
by tmurray 14y ago
B3D PM is fine.
15.
by tmurray 14y ago
I implemented scatter back in October, but it just barely missed Android 4.2. It's in the next release.
16.
by tmurray 14y ago
Desktop: high-end consumer GPUs have about 10-15x the single-precision FLOPs and 4-6x the bandwidth of a single Intel CPU socket. At this point, usually connected via PCIe Gen3. There are two real vendors (NVIDIA and AMD), and what comprise
17.
by tmurray 14y ago
Pretty much exactly this. Performance portability is our main concern, and we are willing to trade off some peak performance to get it because of how badly you will hurt yourself on different architectures. We are trying to solve low-hangin
18.
by tmurray 14y ago
I worked on CUDA at NVIDIA for over four years and was the primary API designer for a large part of that time. I started on RS at Google in September. Basically, he gives us too little credit for the execution model (it's young, it's improv
19.
by tmurray 14y ago
I think it's a political move more than a technical one. WinRT lets MS say to Intel that Intel has to care about the tablet market and low-power processors or otherwise ARM will get a foothold in Windows (giving them easy access to the low-
20.
by tmurray 14y ago
They're blade systems, there's not really room for disks. Easier to keep it centralized and easily serviced.
21.
by tmurray 14y ago
(full disclosure: used to work for NV on CUDA and did very extensive work on Titan, so I am probably biased) If you think your existing MPI app is going to automatically scale to a heterogeneous architecture (high-power x86 on the main CPU,
22.
by tmurray 14y ago
Tesla boards haven't shipped in a separate 1U form factor for a few years; they're all passively-cooled PCIe boards inside a x86 server chassis now.
23.
by tmurray 14y ago
I don't think that is true. If you're writing C, it's probably because you want to be close to the metal and want many of the guarantees that such proximity provides. If you're focused on that sort of thing, then it's definitely useful to u
24.
by tmurray 14y ago
The lack of any sort of physical connection to the NVIDIA GPU's display outputs is the fundamental feature of Optimus. Switchable graphics existed for years before Optimus introduced (and was usually usable under Linux without issue), but i
25.
by tmurray 14y ago
You basically missed the entire point of it or why it's interesting. Current Intel CPUs have a very small GPU built on to the die of the CPU. By buying the CPU, you're paying for an Intel GPU anyway. At the same time, unlike CPU performance
26.
by tmurray 14y ago
Immersion cooling was used on the Cray-2 supercomputer with Fluorinert[1]. Water cooling is fairly common in high-end supercomputing setups (I think all the BlueGene systems are water-cooled, for example). [1] http://en.wikipedia.org/wiki/
27.
by tmurray 14y ago
"falsify" means "to forge or alter as to deceive," not disprove.
28.
by tmurray 14y ago
The hardest part about API design is picking the appropriate primitives in the first place. Use cases are relatively easy--somebody has a problem, come up with a solution--but any solution can be expressed in a myriad of different ways. The
29.
by tmurray 14y ago
oh, I'm not claiming that x86 is going to win in mobile or anything like that. My only point is that based on devices shipping today, the choice of ISA does not cause huge power efficiency disparities and that there's no reason to think tha
30.
by tmurray 14y ago
Why do you assume ARM-based processors will necessarily have a higher perf/W than x86? This has been a common claim (usually because of the perceived size of the x86 instruction decoder), but Medfield has proven that to be false: http://ww

More ›