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22242
bio website fph.altervista.org
location Pisa, Italy
age 31
visits member for 5 years, 1 month
seen 33 mins ago

Numerical linear algebra. Mainly matrix equations and their applications (control theory, applied probability).


12h
reviewed Approve Prehomogeneous vector spaces
Dec
17
revised ULU Decomposition of a matrix
edited tags
Dec
14
comment when can I say that $UV^T$ is a permutation matrix?
If you want to define a "distance from being a permutation matrix", the obvious candidate is $$\min_{P \in \text{Permutation matrices}} \|A-P\|,$$ where $\|\cdot\|$ is a matrix norm.
Dec
13
comment Suggestions for good notation
@J.M. That "Matlab notation" actually first appeared in ALGOL and FORTRAN in the 60s.
Dec
11
revised How to generate $n$ FP32 rationals s.t. no two distinct k-el. subsets have same sum?
added 314 characters in body
Dec
11
answered How to generate $n$ FP32 rationals s.t. no two distinct k-el. subsets have same sum?
Dec
10
revised Batch Markov Arrival Process - Computing Ps(t)
latex + tags
Dec
7
revised Compute adjugate matrix over commutative ring
added 93 characters in body
Dec
7
comment Compute adjugate matrix over commutative ring
@NicolasMalebranche You are correct about the determinant. The algorithm I suggested won't work then. I am still not convinced that there cannot be a simple trick to make those simplifications 'automatically', though.
Dec
5
answered Compute adjugate matrix over commutative ring
Dec
5
comment Compute adjugate matrix over commutative ring
I think that you can run Gaussian elimination keeping the denominators written formally instead of computing them. To compute sums you just reduce everything to common denominator. In the end you'll end up with a "formal denominator" equal to the product of the pivots, that is, the determinant. You just strike it out and it's done.
Dec
1
revised perturbation of Invariant subspaces
clarified some expressions
Dec
1
revised perturbation of Invariant subspaces
added 207 characters in body
Dec
1
answered perturbation of Invariant subspaces
Dec
1
comment Eigenvalues of Symmetric Tridiagonal Matrices
The one in the question is not a Toeplitz matrix.
Nov
28
comment What problem would you base your mathcoin on?
Personally, I would rather see computing power itself treated as a currency. "Hey, I have this computation to make, can you make it? It'll cost 1$ per Tera-operation." Current cryptocurrencies are the computational equivalent of a one-trick pony; there is one single operation to perform, and hardware specialization is encouraged, rather than the use of general-purpose massively parallel computing machines.
Nov
18
awarded  Yearling
Nov
16
comment Open source mathematical software.
Is the list of capabilities missing, or is it the empty set? :)
Nov
16
comment Open source mathematical software.
@kundor Actually the Geogebra page on licensing now seems clearer than when I wrote my previous comment. The program itself is GPL, and the additional restrictions are on additional components such as the web plugin, the installer and the translations of the interface in other languages. I still disagree with the claim "GeoGebra is open source software", but at least everything is consistent.
Nov
16
comment Open source mathematical software.
@kundor Sure, but you cannot forbid those who already have the software from redistributing it (even to commercial users), which usually makes selling it quite pointless. The commercial use clause falls under the "further restrictions" cause and is invalid in my view. And the contradiction (1)-(2) stands clear in the OSI definition, if one assumes that as the definition of open source.