fdej

22 ms·

151.
by fdej 11y ago
Check out the Wikipedia article https://en.wikipedia.org/wiki/Nothing_up_my_sleeve_number for some examples: ARIA uses 1/π (indeed, why not pi?) MD5 uses sin(n) (why not cos(n) or sqrt(n)?) SHA-1 and SHA-2 use squ
152.
by fdej 11y ago
If primes derived from pi are not suspect, then that surely goes for primes derived from 1/pi, e, sqrt(2)... as well? What about bit order, byte order? The problem is that there are lots of small choices involved in picking "nothi
153.
by fdej 11y ago
Very large or small numbers are useful in combinatorics and number theory. It can also happen that they are needed for intermediate steps in an algorithm, even when the inputs and outputs are moderate (the same reason that 15 digits sometim
154.
by fdej 11y ago
Sure, but: 1) As soon as you wrap it in a Python class, much of that speed advantage goes away. 2) Double-double doesn't solve the problem with the limited exponent range of doubles. 3) When the goal is to allow setting the precision t
155.
by fdej 11y ago
It was warmed up.
156.
by fdej 11y ago
Sadly, PyPy doesn't speed up mpmath a whole lot. Edit: I just tested multiplying two 100 by 100 matrices, and got a 5x speedup with PyPy compared to CPython. Which is nice but not amazing.
157.
by fdej 11y ago
Author of mpmath here. It depends a lot on what you're doing. A single floating-point arithmetic operation in mpmath at low precision involves something like 100 "Python cycles" (bytecode ops), each of which takes perhaps 100
158.
by fdej 11y ago
Publishing in the most prestigious journals is hugely important. The first thing many academic hiring/promotion/grant committees look at is how many Nobel Prizes you've won, the second thing is how many publications you have
159.
by fdej 11y ago
PhD in symbolic computation (RISC). Symbolic integration is not my field of research, though, and I don't really know anything beyond the basics (covered in courses on computer algebra). Passively attended plenty of seminars and confer
160.
by fdej 11y ago
There is no complete implementation of the Risch algorithm. None of the implementations fully implement the algebraic case. Besides, the Risch algorithm doesn't solve all symbolic integration problems in practice: * Even when it succee
161.
by fdej 11y ago
2^34240923842043983204982-1 is divisible by 3.
162.
by fdej 11y ago
Because GMP is designed for arbitrary size integers, and for safety. Given two mpz_t operands to multiply, it needs, in some order, to: * Dereference pointers * Extract the signs of both input operands * Extract the sizes (number of limbs)
163.
by fdej 11y ago
Why does it need to be updated? Valgrind is that rare piece of software that always has been working absolutely flawlessly for me.
164.
by fdej 11y ago
The scanned area is still just 1/1000 of the Indian Ocean, and very far from the coast. Finding two ships doesn't sound so bad to me.
165.
by fdej 11y ago
A stackexchange site with an automatically posted "question" for each arxiv submission would be an interesting idea.
166.
by fdej 11y ago
This is less of a problem when you consider that peripheral functions tend to have verbose, descriptive names. Is GeoProjection really fundamentally worse than Geo.Projection? The upper case convention by itself greatly reduces the chance o
167.
by fdej 11y ago
Nice project. I wonder, would https://commons.wikimedia.org/wiki/Category:Caricatures_by_L... appear as funny to a blind person as they are to a seeing person?
168.
by fdej 11y ago
It seems to me that all we really need is a way to attach reviews/endorsements to papers already posted on the arxiv. Tim Gowers's initiative is a good start, but with just one specific overlay journal, a tiny one.
169.
by fdej 11y ago
Thanks for the correction! I just came across tested.com a few months ago, and probably wouldn't have found it without the 'big names'.
170.
by fdej 11y ago
I loved MythBusters early on, but I haven't been able to stand watching the show for several years, save for the occasional episode. You know the drill: the heavy editing, the grating narrator, the scripted conversations, the sponsored
171.
by fdej 11y ago
Some of us need would need to run for an hour just to get away from the city blocks. Well, I'm currently fortunate enough to have a park just nearby, though it's a rather small and boring park... nothing like living next door to a
172.
by fdej 11y ago
Sage doesn't really use SymPy a whole lot. Most of the core algebra in Sage is based on C libraries like MPIR, Flint, Singular, Pari... Nemo uses some of the same libraries under the hood, but there's much less overhead. This is i
173.
by fdej 11y ago
Not necessarily the most representative benchmark, but: >>> from sympy import * >>> from time import clock >>> var('x y z t') (x, y, z, t) >>> f = poly(1 + x + y + z + t)
174.
by fdej 11y ago
My impression living in France for the last year is very similar to yours. It's the mecca of paperwork (but doing taxes was relatively easy). And if you're required to supply some documentation from another country, you're li
175.
by fdej 11y ago
This is not quite correct. A finite ring can only have finitely many primitive roots of unity, so the length of the FFTs you can compute in a ring of fixed size is bounded. To compute arbitrarily long convolutions over a finite ring, you ne
176.
by fdej 11y ago
Indeed, having a fast way to multiply in Z[x] gives you a fast way to multiply in Z and vice versa. In the reverse direction, you can encode the polynomial f = 2x^2 + 6x + 3 as 30602, and 30602^2 = 936482404 tells you that f^2 = 4x^4 + 24x^
177.
Computing Bell numbers(fredrikj.net)
17 points by fdej 11y ago|0 comments
178.
by fdej 11y ago
I guess we'll be removing cruft from the web.
179.
by fdej 11y ago
110000 BOE per day = 7.78 GW. An estimate from 2013 cited on Wikipedia claims the cost of the vessel is US$10.8 to 12.6 billion. Is there a reliable estimate of how much solar power you could install for the same cost?
180.
by fdej 11y ago
Basically everything that can be done with 80-bit floats can be done with techniques such as compensated summation and double-double arithmetic. This requires several 64-bit operations per operation, but those operations can take advantage

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