brucedawson

29 ms·

301.
by brucedawson 11y ago
GPUs are happiest when doing float precision, which is 24 bits. Most GPUs can, at reduced speed, do double precision, which is 53 bits. The maximum precision for this zoom movie is 960 bits. So, unless you write code to compose high-precisi
302.
by brucedawson 11y ago
If you are trying to get exact compatibility between systems with different floating-point systems then serializing to text is the least of your problems.
303.
by brucedawson 11y ago
If you want compatibility between x86 CPUs and ARM/PowerPC/MIPS then you have to not use the extended 80-bit results. The 80-bit results can be more accurate (although not always, it depends on exactly how they are used) but the O
304.
by brucedawson 11y ago
It's not impossible, it's just hard. I covered the things you have to worry about a while ago in this article: https://randomascii.wordpress.com/2013/07/16/floating-point-... As long as you avoid un
305.
by brucedawson 11y ago
People keep on misusing strncpy which is why people keep blogging about it. I wrote about it two years ago after running across one too many abuses: https://randomascii.wordpress.com/2013/04/03/stop-using-strn
306.
by brucedawson 12y ago
> someone can get SYSTEM access on a windows machine just by getting someone to visit that site in Chrome? Or, I believe, through any of the other Windows browsers. There was nothing Chrome specific about getting SYSTEM access. All brows
307.
by brucedawson 12y ago
Lee is clearly extremely talented. He wouldn't be making 'standard' salaries, he'd be getting paid extremely well. And, I imagine he'll be getting some pretty impressive job offers now...
308.
by brucedawson 12y ago
Cool. It's fascinating that the most effective ways of reducing the frequency of account hijackings is not to make them more difficult, but to make them less rewarding. Although, when I summarize it like that it does seem kind of obvio
309.
by brucedawson 12y ago
I think NaNs tend to pollute results more effectively than denormals. However NaNs can be trapped easily by enabling the appropriate floating-point exceptions so that they turn into crashes. Note that on most CPUs flush-to-zero is a CPU sta
310.
by brucedawson 12y ago
I've got no silver bullet for that. Recently I found a bunch of functions that were running slower on Windows. I eventually proved that their code had not changed and they were being run the same number of times as before. I had to use
311.
by brucedawson 12y ago
Update: did somebody say they wanted a better UI for Linux perf? I just saw this: http://www.rotateright.com/zoom-release-notes/ In particular: Removed licensing restriction: Zoom is transitioning into a free software
312.
by brucedawson 12y ago
You called? I didn't know you did Windows profiling. I do some profiling on Linux, although nowhere near as much as on Windows. My observations of the differences are: I love how easy it is to measure CPU performance counters on Linux,
313.
by brucedawson 12y ago
The page-zeroing code may be able to minimize its effect on the cache, but it will then necessarily consume memory bandwidth -- 4 KB of bandwidth per page zeroed as it writes each page. So, it still affects overall performance. And it guara
314.
by brucedawson 12y ago
A hundred cycles to zero a page? If 4 KB can be written in a hundred cycles then, assuming a 3 GHz processor, that's 30 million pages per second or ~120 GB/s. That's pretty fast memory. On x86/x64 processors, which lack
315.
by brucedawson 12y ago
What alternative are you suggesting? Any finite precision numbers will have most of the same problems as IEEE floats. Decimal numbers are a specific case -- assuming them by default would be worse in some ways.
316.
by brucedawson 12y ago
The round-tripping behavior is certainly cool, but my favorite float-fact is still this one: double pi = 3.14159265358979323846; printf("pi = %.33f\n + %.33f\n", pi, sin(pi)); sin(double(pi)) is equal to the error in the double(
317.
by brucedawson 13y ago
> You need to reduce the parallelism in your build. I looked at your blog post and it recommends using /MP and setting num. parallel project builds to num. cores. In other words, you recommend exactly what I was doing! We do use pre
318.
by brucedawson 13y ago
There are a huge number of double-precision NaNs in the absolute sense -- there are 2^54-2 of them. But they are a small portion of all of the doubles (roughly 1/2048) so omitting them from the tests does not help significantly with sa
319.
by brucedawson 13y ago
Amateur. Scale to [0,FLT_MIN*2]. There they are truly most dense, and the density is uniform across the entire range. It's almost like using 24-bit integers.
320.
by brucedawson 14y ago
App Verifier just moves HeapAlloc allocations, but the C/C++ functions default to using these, so it grabs pretty much everything. For game development I wrote a custom allocator that redirects all of our allocations to the Windows heap ins
321.
The crashing bug in VC++ 2012's bug finding feature(randomascii.wordpress.com)
35 points by brucedawson 14y ago|3 comments