On Sat, Jan 10, 2015 at 11:46 PM, Tobias Knopp
tobias.kn...@googlemail.com wrote:
I am already using iterative solvers for my problem. Interestingly the
Kaczmarz method provides extremely good results for my matrix. Since it is
challenging to choose lambda and the number of iterations in
Hi Tobi,
I think cholfact(X'X + lambda I)\(X'y) should work: X'X is positive
(semi-)definite, lambda*I is positive definite for lambda0, and the
sum of any two positive definite matrices is also positive definite.
Alternatively, if you're worried about the numerical conditioning of
X'X, you can
Right, that makes sense. When I asked about rescaling I was wondering
about how floating point roundoff affects the consistency of
predicates before and after transforming points by a scaling/offset to
put the coordinates into the range 1-2. I think what you're saying is
that yes, consistency
This is pretty cool. Writing a robust set of geometric predicates
requires quite an attention to detail.
Some questions:
Restricting to the float range 1.0=x2.0 essentially makes the input
a fixed point representation, with fixed point scaling factor eps(1.0)
= 2.220446049250313e-16. How does
On Sun, Jun 29, 2014 at 1:06 AM, Milan Bouchet-Valat nalimi...@club.fr wrote:
One solution I thought of is to create a workhorse function
do_freqtable(weights, subset, x...), which would be specialized on types. It
sounds like a bit like working around a limitation of keyword arguments, but
it
On Tue, Jun 3, 2014 at 1:13 PM, Chris Foster chris...@gmail.com wrote:
So you can compute the real part L of the Cholesky decomposition exactly as
usual. Given that you now have L, you want the lower triangular matrix M.
Because L and M are lower triangular that's actually quite easy: matrix
On Wed, Jun 4, 2014 at 2:12 AM, Chris Foster chris...@gmail.com wrote:
fiddling with Base.BLAS.dot only got me as far as a segfault so far.
Actually I think I've fixed that now in the gist and using BLAS.dot
directly is faster, though still not very impressive. According to
@time, I've still
for the result of the decomposition?
Cheers, Kevin
On Tuesday, June 3, 2014, Chris Foster chris...@gmail.com wrote:
On Wed, Jun 4, 2014 at 2:12 AM, Chris Foster chris...@gmail.com wrote:
fiddling with Base.BLAS.dot only got me as far as a segfault so far.
Actually I think I've fixed that now
On Tue, Jun 3, 2014 at 4:43 AM, Thomas Covert thom.cov...@gmail.com wrote:
I was hoping to find some neat linear algebra trick that would let me
compute a DualNumber cholesky factorization without having to resort to
non-LAPACK code, but I haven't found it yet. That is, I figured that I
could
also worked out a similar derivation - though I
wasn't able to prove to myself that the equation B = L*M' + M*L' has a
unique solution for M.
This feels similar to the Sylvester Equation, but its not quite the same...
On Mon, Jun 2, 2014 at 10:13 PM, Chris Foster chris...@gmail.com wrote
The problem here is that . isn't defined as an operator, so there's
no broadcasting form of at all. At a guess I'd say that's just an
oversight, in which case making a github issue is the right thing.
On the other hand, the broadcasting versions of .* etc are all defined
on generic
Hopefully encouraging less fancy metaprogramming stuff means simpler
library implementations which actually feel like they're written in
the language. It's a real pain when you have to learn a new DSL for
every library implementation you want to understand (I say this having
read a lot of C++
I'm also pretty excited about using the rift for scientific/technical
visualization (I have a DK1), but so far that hasn't been reflected by
an appropriate amount of spare hacking time.
If you haven't already, I'd recommend checking out the VRUI youtube
demos (for example, this one is pretty
On Mon, May 19, 2014 at 11:44 PM, Chris Foster chris...@gmail.com wrote:
I think these last two points probably generalise to 1D, 2D and 3D data.
IMO there's a case to be made for a simple default GUI with a capable
camera model and control over data set visibility. This would go a long
way
On Sat, May 17, 2014 at 9:59 PM, Hans W Borchers hwborch...@gmail.com wrote:
Yesterday I implemented a function calculating arc length of curves (to the
last digit) when I came across the following stumbling blocks. Image the
following function where I leave a for-loop with a 'break' statement:
On Sat, May 17, 2014 at 11:14 PM, Hans W Borchers hwborch...@gmail.com wrote:
and it took me some time before I realized that the answer came from outside
the function.
That behavior can really lead to very difficult testing situations.
Fair enough. I suspect there can be some subtle bugs
Huh, at first I thought this could be done with a macro (not that I'd
recommend using any such macro in actual code!), but when I tried I
couldn't quote an incomplete block:
julia :(end)
ERROR: syntax: unexpected end
Looking at the underlying Expr for :(begin end) it becomes clear why
this is:
On Thu, Apr 24, 2014 at 7:52 PM, Isaac dux...@gmail.com wrote:
The rand(1) in julia always produces an array rather than a number
in Matlab.
In matlab a scalar is the same as a 1x1 matrix. Luckily julia doesn't
insist on any such madness... try rand() instead :-)
Is it the zlib implementation in the function crc32() you're comparing
to? Taking a peek in the zlib source, it looks like they do a fair
bit of manual loop unrolling and also process the CRC 4 bytes at a
time. Given those differences, the speed difference might not be so
surprising.
On Thu,
On Fri, Apr 11, 2014 at 6:44 AM, Laszlo Hars laszloh...@gmail.com wrote:
note that the running time does not change with a partial loop unroll, like
this:
~~~
function signed_loop{D:Unsigned, A:Unsigned}(::Type{D}, r::A, data,
table::Vector{A})
local j = 0
for i = 1 :
On Sat, Mar 22, 2014 at 9:23 AM, Stefan Karpinski ste...@karpinski.org wrote:
I kind of like that idea, actually.
On Fri, Mar 21, 2014 at 5:10 PM, Matt Bauman mbau...@gmail.com wrote:
I quickly acclimated to Stefan's idiom and now happily read and write
code containing it. That said, it
the attraction as a one liner
though.
-Jacob
On Mar 21, 2014 9:52 PM, Chris Foster chris...@gmail.com wrote:
On Sat, Mar 22, 2014 at 9:23 AM, Stefan Karpinski ste...@karpinski.org
wrote:
I kind of like that idea, actually.
On Fri, Mar 21, 2014 at 5:10 PM, Matt Bauman mbau...@gmail.com wrote
On Thu, Mar 20, 2014 at 7:24 PM, Cristóvão Duarte Sousa
cris...@gmail.com wrote:
Although the short-circuit is more or less known among several programming
languages, I don't think it's that readable outside of an if.
Maybe after a while one starts to read that code as if then, but it's not
so
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