# Questions tagged [performance]

Questions about the execution speed and memory usage of algorithms, data structures, languages and libraries.

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### To what extent is generic and meta-programming using C++ templates useful in computational science?

The C++ language provides generic programming and metaprogramming through templates. These techniques have found their way into many large-scale scientific computing packages (e.g., MPQC, LAMMPS, CGAL,...
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### What is the fastest way to compute all eigenvalues of a very big and sparse adjacency matrix in python?

I'm trying to figure out if there is a faster way to compute all the eigenvalues and eigenvectors of a very big and sparse adjacency matrix than using scipy.sparse.linalg.eigsh As far as I know, this ...
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### Kronecker product among multiple arrays

I was wondering whether there is a smart and efficient way in Matlab to compute the kronecker product of several 1D arrays. What I mean is something like this ...
185 views

### Sign of integer determinant 4 by 4

I'm in the context of this publication: http://www.gilbertbernstein.com/resources/booleans2009.pdf I applied quantization to my point coordinates: All coordinates are integer lying in [0, 2 power 20]....
2k views

### Loop optimization with f2py, Cython and Numba

I tried to used f2py, Cython and Numba to make a simple loop structure be faster in python. Python implementation: ...
606 views

### Vectorizing Matrix Multiplication

I would like to do the following operation: I have a "4D" matrix A and a "3D" matrix B. Both A and B are actually 2D matrices, where for A, each element is a 2D matrix, and for B, each element is a 1D ...
2k views

### What tools or approaches are available to speed up code written in Python?

Background: I think I might want to port some code that calculates matrix exponential-vector products using a Krylov subspace method from MATLAB to Python. (Specifically, Jitse Niesen's expmvp ...
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### Optimized parallel routine for $X' W X$ with $W$ diagonal

$X$ is a dense matrix of real doubles, typically of size 20 million rows and 500 columns, and $W$ is a diagonal matrix of real, non-negative doubles stored as a vector. I'm working in C and have ...
1k views

### Open source implementation of rational approximation to a function

I am looking for some open source implementation (any of Python, C, C++, Fortran is fine) of rational approximation to a function. Something along the article [1]. I give it a function and it gives me ...
270 views

### Literature references for modeling current and future energy costs of floating-point operations and data transfers

I am searching for the most important literature and slide references for modeling current and future energy costs of floating-point operations and data transfers across the CPU, memory, network, and ...
3k views

### What is the overhead in sparse matrix multiplication

Does matrix multiplication (both Mat*Mat, and Mat*Vec) scale with number of non-zeros, or with the size of the matrix? Or some combination of the two. What about with shape. For example, I have a ...
4k views

### What is the fastest opensource implementation of Bessel functions computation?

I'm looking for an open-source (to use and learn from) software which computes Bessel functions of integer order of real argument to double precision the fastest among all such implementations. ...
660 views

### Simple Runge-Kutta Scheme for nonlinear PDE

I am new to this community as well as to scientific programming. I programmed a simple 4th order Runge-Kutta for the 1-D Cahn-Hilliard Equation for some first simple calculations on pattern forming ...
119 views

### Can other running processes harm the performance of my simulation?

I don't have an high-end machine on which run my simulation (Python + C extensions, based on numpy for calculations) Thus I intend to run the program on my PC, for several hours. I won't use the ...
159 views

### Choosing hardware to use with PETSc

I would like to know more on choosing hardware to get the maximum price/performance when using the PETSc library (and various third-party preconditionners) I am currently working on a 2 cpu (2*E5-...
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### Performance of adding eight numbers sequentially vs. in a tree

The simplest way to add 8 numbers would be something like this, sum = one + two + three + four + five + six + seven + eight; This (in C) would add ...
113 views

### fastest and most efficent way to count all combinations in many sets and sum them together

I am a Java programmer who has reached the limits of brute computer power. My relational database (and non relational databases) is not producing results quick enough and I have hit a bottleneck in ...