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Questions tagged [lanczos]

29 questions
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SIMD-exploiting implementation of Peterson and Monico's Lanczos algorithm over the field with two elements

(This question is probably flirting with the "no software recommendations" rule; I understand why it might be closed). In their paper F_2 Lanczos revisited, Peterson and Monico give a version of the Lanczos algorithm for finding a subspace of the…
gspr
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Rough Edges With Lanczos Resampling in Golang

I've been writing some basic methods to resize images in Golang. I've seen several posts about resizing images, but for the life of me I can't figure out what I'm missing... Essentially, my issue is that when resizing an image in Golang, my results…
Anish Goyal
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Lanczos interpolation in C

i need to implement the following formula in c-code: https://en.wikipedia.org/wiki/Lanczos_resampling Therefore i'm using the multidimensional interpolation approach: where L(x-i) or L(y-i) is: I'm using the ppm image format to get rgb values…
Felix K.
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Lanczos scale not working when scaleKey greater than some value

I have this code CIImage * input_ciimage = [CIImage imageWithCGImage:self.CGImage]; CIImage * output_ciimage = [[CIFilter filterWithName:@"CILanczosScaleTransform" keysAndValues: kCIInputImageKey, input_ciimage, …
Logioniz
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Lanczos Resampling error

I have written an image resizer using Lanczos re-sampling. I've taken the implementation straight from the directions on wikipedia. The results look good visually, but for some reason it does not match the result from Matlab's resize with Lanczos…
kip622
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Initial Vector in Krylov-Schur diagonalization in mkl sparse eigensolver

I have an university project that involves the diagonalization of large sparse matrices, I decided to use Fortran and I'm using ifx intel fortran compiler with mkl lapack interface. The project requires to use Lanczos or similar algorithms, so I'm…
VINCENZO BISOGNO
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OpenCV homography - question about deringing lanczos interpolation

I'm attempting to improve performance of the OpenCV lanczos interpolation algorithm for applying homography transformations to astronomical images, as it is prone to ringing artefacts around stars in some images. My approach is to apply homography…
Adrian K-B.
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Plot 1D Lanczos Interpolation

Imagine we have the following points: x = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] y = [2, 3, 5.5, 6.5, 5, 4, 5, 7.5, 8, 7] Now we want to interpolate every point using lanczos interpolation like: lanczos_interpolation = lanczos_interpolation(x, y) xs =…
Janikas
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How to Get Frequency Window from Lanczos Filter

I have this code for a Lanczos filter: dT = 1 % sampling interval Cf = 1/40 % cutoff frequency fl = 100 % ? M = 100 % number of coefficients ? not sure about number LoH = 1 % low pass Nf=1/(2*dT); %Nyquist frequency % Normalize the cut off…
rose_t
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Sparse matrix diagonalisation using Numpy Linalg package

What is the maximum size of a sparse matrix that can be diagonalized using Numpy Linalg package? I have been working with exact diagonalisation methods such as Lanczos and Arnoldi in the context of diagonalizing my Hamiltonian matrices. Recently I…
Fracton
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scipy's sparse eigs yielding wrong eigenvectors

I am a bit confused regarding the following issue: I am computing fixed points of a quantum channel, which means I want to compute the leading eigenvector of a specific matrix. The matrix is such that its dimensionality is n^2 x n^2 and defined in…
sani
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Image Down scaling in C#

I am reducing image size to 8*8 to compute average hash to find similar images using C#. I am planning to use Lanczos algorithm to reduce the image size, as it seems to give good results (read from the internet and also python image hashing algo…
Hemanath
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OpenMP matrix-vector multiplication on-the-fly in Fortran

I am writing a Fortran code to carry out a matrix-vector multiplication. The multiplication is carried out on-the-fly in the sense that the matrix elements are not stored beforehand. The code goes well in the serial case, but when I implement the…
user45857
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getting a segfault coredump when restarting the Lanczos method after 3 iterations

So I'm working on the convergence of Lanczos algorithm. I implemented it in C language, I first calculate both the matrix V which is the orthonormal associated to the Krylov subspace, and the Triadiagonal symetric matrix T, after that I compute the…
Adil
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