alnsn
Joined 12 years ago
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18
Member since
Jun 18
[ my public key: https://keybase.io/alnsn; my proof: https://keybase.io/alnsn/sigs/WofgAIgnyTwitw2Hd49I1sBdXTHzXQHdlwqdnEl5rRY ]
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Comment · 2 days ago
You can ask Claude to cross-complie, prepare an image (aka install) and run an emulator. I tried exactly this yesterday and in about an hour I could attach to tmux and run tests on emulated riscv64 board.
Comment · 9 months ago
Related: Why there are holes in bicycle rims: https://youtu.be/yppBwvPciBo?t=8m7s
Comment · 1 year ago
Comment · 7 years ago
Space optimal isn’t necessarily the fastest.
Note that PostgreSQL code uses 2-graph instead of a more compact 3-graph version. The latter is noticeably more compact: 1.25 vs 2.1 factor.
Comment · 7 years ago
It’s down to a quality of implementation. I can give you some hints on improving it if you’re interested.
A tiny JIT code generator inside cdb would definitely bring performance on par with a generated C code but it’s probably an overkill.
Comment · 7 years ago
Not sure that scares you, code generation or a choice of scripting language?
If you want to avoid a code generation, you can generate a .cdb (constant database) file with the cdbw(3) C API and read it using the cdbr(3) C API.
cdbw(3) http://netbsd.gw.com/cgi-bin/man-cgi?cdbw+3+NetBSD-current cdbr(3) http://netbsd.gw.com/cgi-bin/man-cgi?cdbr+3+NetBSD-current
Some examples of .cdb files on NetBSD:
/usr/share/misc/terminfo.cdb /var/db/services.cdb
If you don't like a particular choice of a scripting language, you can adapt my Lua script:
https://gist.github.com/alnsn/68f599bc9358fcee122d6175392d77...
Building and peeling a graph should be identical but the assign step is different. I use non-minimal not order preserving BDZ scheme while Joerg's code is based on the original CHM scheme.
Given keys A, B, C and D, CHM always maps them to values 0, 1, 2 and 3. BDZ, on the other hand, can generate values in a range [0, 2.1 * 4) and it doesn't preserve an order. For instance, one possible mapping in the BDZ scheme is 7, 2, 5, 1.
Alex
Comment · 11 years ago
This is going to be interesting. Rust on top of rumprun bare-metal unikernel
https://twitter.com/gandro23/status/645734117699624960
Comment · 11 years ago
> Many other free software projects, including FreeBSD, NetBSD, and OpenWrt, are moving in the same direction.
I might be wrong (I'm away from my NetBSD boxes) but build.sh script in NetBSD has a buildseed option which can be used to create identical builds of the base system.
Comment · 11 years ago
I spent about an hour looking at the tool. They say that only very few instructions aren't supported (and thus ignored by the tool) but a very popular imul instruction can be ignored.
PS I noticed that gcc with -march=corei7-avx generates more cycles compared to a generic amd64 compilation for an unrolled integer(4) to char[4] conversion.
Comment · 11 years ago
You can start from here http://lambda-the-ultimate.org/node/3851#comment-57805 or read the whole thread.
Comment · 11 years ago
This one?
#include <boost/math/tools/remez.hpp>
I used some bits from it to help me in building my own log approximation but I didn't have time to dig into it.
I ended up doing Chebyshev approximation over [1, 2) interval but I extended the interval slightly to make sure that an error term at 1.0 is minimal (you can also minimise an error term at 2.0 if you want some smoothness between [1, 2) and [2, 4) intervals).
It's easy to calculate new interval values for Chebyshev approximation and it shouldn't be a problem to modify Remez but I couldn't find any Remez implementation that would let me do what I needed.
Usually, interval ends in Remez algorithm are fixed, while internal points can be moved by the algorithm. I needed a way to to fix one or two internal points (1.0 and optionally 2.0) but let the algorithm move interval ends within certian limits.
If anyone knows of any tool that let me do it, I'd be happy to play with it and publish my code. My approach is a bit similar to [1] but I'd more likely use Intel assembly or DynASM.
[1] http://gallium.inria.fr/blog/fast-vectorizable-math-approx/
PS The author of [1] uses remez from e Sollya tool but it doesn't let me fix internal points. I looked at the implementation but it's more obscure than boost/remez.
UPDATE: it's not clear from the above what my objectives were. I wanted to to produce exact values for integer powers of 2 including log2(1). This approach also gives a small relative error around x=1.
Comment · 11 years ago
I once spotted a plane going circles over North London.
https://mobile.twitter.com/nasonov/status/484027620993273857...
Comment · 11 years ago
Indeed, it has been discussed many times. But I don't remember any discussion on attribution rights. If GS replaced GPL text with their own header they presumably deleted names of the original authors. I wonder if those authors could (collectively perhaps) send a complaint to GS and ask to restore the attributions?
Comment · 11 years ago
It depends on how much effort you put in making sure your parser is robust. I ran AFL tests for several days trying to find bugs in Lua parser but AFL kept discovering a way to load a binary chunk. After that, it didn't take to crash on a malformed binary chunk.
Priv separation is a good idea even if you trust your parser.
Comment · 11 years ago
Why [0, 1] interval is so popular in random number generators? It's one of the worst intervals possible imo because it includes subnormal numbers. The interval [1, 2] is much nicer. Some implementations generate random numbers in [1, 2] and subtract 1.0: http://permalink.gmane.org/gmane.comp.lang.lua.luajit/3051