4,440 questions
2
votes
1
answer
126
views
PCA with arpack returns different values when the order of observations change, but why?
I have recently noticed that when I change the order of the observations in a sparse array, scikit-learn PCA with svd_solver="arpack" returns different floating point numbers. Is this an ...
- 23
0
votes
3
answers
128
views
Database Rows to static columns [closed]
I have a single column DB file that is rigidly formatted. It doesn't have a header or field names in the export that I've imported into a Goggle Sheet. I need help with how to approach this task of ...
- 379
1
vote
2
answers
98
views
Confused about how tf.keras.Sequential works in TensorFlow – especially activation and input_shape
I'm learning TensorFlow to build machine learning models in Python. I tried following the official documentation on creating a simple classification model, but I couldn't clearly understand the tf....
- 45
6
votes
1
answer
116
views
Efficient filtering of sparse matrix from full
I have a large, full, dense, symmetric matrix (eg 30k² or 60k² positive elements, ~100% density). I want to extract either (i) the top (eg) 1% highest values; or (2) the values above a user-specified ...
- 639
0
votes
0
answers
52
views
MICCG(0) for a fluid simulation fails at Neumann boundaries
I am trying to follow Robert Bridson's Fluid Simulation Notes (https://www.cs.ubc.ca/~rbridson/fluidsimulation/fluids_notes.pdf) to implement my own eulerian fluid simulator for the first time.
I was ...
- 11
0
votes
1
answer
58
views
how to use mkl_dcsrgemv or other functions in OneAPI to cal. scalar prodoct between mass dim sparse matrix and vector?
I program in fortran with Intel OneAPI compiler ifx and MKL packages.
I want to cal. the scalar product between a mass dim sparse matrix and a vector.
When the dim of the sparse matrix could be ...
0
votes
1
answer
126
views
It is possible to compute both the size and values for a std array in a constexpr function?
I am trying to express the structure of a sparse matrix (and the structure resulting from sparse matrix operations) at compile time with template parameters and constexpr functions.
I've defined this ...
- 41
1
vote
2
answers
93
views
How to exploit sparsity with lists in a Cython function
I have a function I need to implement which does not vectorize well, and so I am implementing it in Cython to make the nested for-loops workable. My problem is of a similar complexity as naive matrix-...
2
votes
0
answers
195
views
How to reuse cuDSS factors when solving a system of linear equations Ax=b
I am using cuDSS to solve a set of Ax=b equations as follows
cudssMatrixType_t mtype = CUDSS_MTYPE_SPD;
cudssMatrixViewType_t mview = CUDSS_MVIEW_UPPER;
cudssIndexBase_t base = CUDSS_BASE_ZERO;
...
- 83
1
vote
1
answer
76
views
scipy.sparse: one subarray at many locations in a larger array
Say I have a sparse subarray whose contents and shape are known:
import scipy.sparse as sp
sub = sp.coo_array([[a, b], [c, d]])
I'd like to place this subarray at many locations, according to some ...
2
votes
1
answer
116
views
How to convert Eigen Sparse Matrix to Cuda CuSparse Matrix
I am trying to convert an Eigen Sparse Matrix of size NxN to CuSparse matrix so that I can use CUDA to solver the matrix Ax=B. Came across this thread which is pretty old (Convert Eigen::SparseMatrix ...
- 83
1
vote
1
answer
106
views
How to efficiently multiply a vector by a transposed sparse matrix in Eigen?
I have with a sparse matrix A and a vector x in Eigen, and I need to perform the following transposed matrix × matrix × vector operation: ATAx. This can be decomposed into two matrix-vector ...
- 24.2k
1
vote
1
answer
57
views
How to produce tensor of first occurrencies of another tensor using PyTorch
Let's say we have an ordered 1D tensor of ints/longs t.
I want to produce a new tensor a with size max(t) where each term a[i] contains the first occurrence of the value i in the tensor t.
We could ...
- 146
4
votes
2
answers
131
views
Identifying and removing duplicate columns/rows in sparse binary matrix in PyTorch
Let's suppose we have a binary matrix A with shape n x m,
I want to identify rows that have duplicates in the matrix, i.e. there is another index on the same dimension with the same elements in the ...
- 146
0
votes
1
answer
68
views
Matrix free arnoldi
I want to do a "matrix-free eigenvalue evaluation" of a unitary matrix using ARPACK package. Unitary matrix comes from a sparse hermitian matrix, something that happens in many-body problem.
...
- 103