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Numerical algorithms for problems in analysis and algebra, scientific computation

1 vote

What software one needs to solve a big linear system on a small computer?

Mathematica will do this with no problems (actually, you can use your GPU to do it REALLY fast). Unlike Maple (apparently) there is no problem getting mathematica to use floating point computation, bu …
Igor Rivin's user avatar
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2 votes

Simplex interval analysis

A typical operation is an affine transformation. The set of simplices is preserved by this, the set of balls is not.
Igor Rivin's user avatar
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2 votes

Eigenvalues of monomial matrices

No. If $P$ is the matrix of a transposition (2 by 2) and $D$ is $diag(1, -1)$ the eigenvlues are imaginary.
Igor Rivin's user avatar
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2 votes

Partitioned Runge-Kutta (Lobatto IIIAB)

Google says: L. Abia and J. M. Sanz-Serna, Partitioned Runge-Kutta Methods for Separable Hamiltonian Problems, Mathematics of Computation Vol. 60, No. 202 (Apr., 1993), pp. 617-634, doi:10.2307/21531 …
Igor Rivin's user avatar
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6 votes

show that $ \frac{\Gamma(\frac{1}{24})\Gamma(\frac{11}{24})}{\Gamma(\frac{5}{24})\Gamma(\fra...

This follows from the discussion at and preceding page 31 in Campbell's book.
Igor Rivin's user avatar
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4 votes
Accepted

Finding the smallest eigenvalues of a large, but structured, matrix

Well, if you add $c I$ to your matrix, for some reasonable value of $c,$ it will become nonsingular. As for the left inverse, since your matrix is sparse, to compute the backward iteration you can use …
Igor Rivin's user avatar
  • 96.4k
2 votes

Estimating the volume of a semialgebraic set from above

Here is an algorithm: partition $\mathbb{R}^n$ into cubes of side $1/k.$ For each cube $C_i$, use your favorite quantifier elimination algorithm to check whether the set $S$ intersects it. Then, your …
Igor Rivin's user avatar
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1 vote

numerical methods for matrices (method of full reduction)

I have never heard of the "method of full reduction" (neither has Google), but a standard textbook on matrix computation is... "Matrix computation", by Golub and van Loan. For sparse matrix stuff (alm …
Igor Rivin's user avatar
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1 vote

Numerical integration over 2D disk

An insufficiently well-known (so, perhaps slightly beyond the state of the art) integration algorithm can be found in the paper of O. Jenkinson and M. Pollicott entitled "A dynamical approach to accel …
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3 votes

There must be a good introductory numerical analysis course out there!

Numerical analysis is a big subject... Stephen Boyd's Convex Optimization (available for download on his web page, or in two pound form from CUP) is a very lucid book, covering both applications and t …
1 vote

Computational complexity of integration in two dimensions

This paper seems to be a good reference: Average Case Complexity of Weighted Integration and Approximation over $\mathbb{R}^d$ with isotropic weight, by Plaskota, Ritter, Wasilkowski. Of course, the …
Igor Rivin's user avatar
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1 vote

Error in Polynomial Root Finding Algorithm with Synthetic Division

Books have been written about this. The primitive implementation of this is going to be terrible, but some tweaks (see this wikipedea article, and references therein) work ok.
Igor Rivin's user avatar
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6 votes

How to solve a fifth degree polynomIal

This is described in painful detail here.
Igor Rivin's user avatar
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3 votes

Solving over-determined system of polynomials

I am not sure I understand what the ellipsis $\dots$ means in the last set of equations, since it seems that you only have pairs $l_i, u_i.$ If that is true, that means that there are $2^n$ possible v …
Igor Rivin's user avatar
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14 votes
Accepted

How to compute $\sum_{x \in \mathbb{Z}^n} e^{-x^TMx}$ efficiently

You are trying to compute a multi-dimensional theta function, and this question is studied in depth in this 2003 Math. Comp. article by Deconinck, Heil, Bobenko, van Hoeij,and Schmies.
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