# Questions tagged [c]

C is a general purpose programming language. Originally intended for implementing system software, C and its close relatives are the principle languages used in most modern operating systems. Due to its thin layer of abstraction and low overhead, C allows efficient coding of algorithms and data structures useful for scientific computation. Use this tag for questions involving the C programming language.

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### Heineken Virus C program ( how to simplify and discard else if in my code)

So I have a question about simplifying my C code , This is the question : A pandemic of the Heineken virus is underway in Croatia and around the world. The National Civil Protection Headquarters plans ...
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### How to document math formulations in scientific computing codes?

I am writing the code relate to math. There is some complicated math formulation in the project. Directly writing the calculation code leads to hard understanding; thus I want to comment on the ...
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### Augmented arithmetic operations (IEEE-754-2019): output definition and implementation

In the new version of IEEE-754-2019: IEEE Standard for floating-point arithmetic, the augmented arithmetic operations were introduced. These operations can be particularly useful in certain numerical ...
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### Performing 2d numerical integration with Boost Cpp

I've been learning to use the numerical quadrature of the Boost library for Cpp. In the documentation, I've found an example for 1D Gauss-Kronrod Quadrature using Boost. ...
73 views

### 2d Schrodinger Equation via matrix diagonalization in C

I am trying to solve the time-independent Schrodinger equation in two dimensions via discrete matrix diagonalization. I want the energy eigenvalues and the corresponding eigenfunctions for a given ...
30 views

### Alternatives to breadth-first-search in 3D grid cluster detection?

I've got a question about a good way to find the quickest algorithm for my problem: problem: I've got a 3D cubical grid containing voxels that are either 1 or 0. It is stored as a flattened array. If ...
92 views

### Best way to check if SOR solution has converged for 2d matrix

I have written a SOR algorithm to solve the Laplace equation on a 2d grid. The outside of the grid is fixed at 0 and the central square is fixed at 10. I can obtain the fully converged solution for ...
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### GPGPU computing, software selection

I am using an existing GCC C++ x86 Qt application that filters, displays and stores results computed by some C code. Since the computation by now got too complex for CPUs I intend to port the small C ...
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### Evaluate Nth root of a rational to a correctly rounded float

Excuse my lack of vocabulary for I have no formal training in this field, which is also why I ask this question - it may be trivial or it may be impossible. I want to evaluate an expression in the ...
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### Reducing run time of a numerical calculation using a mex file in Matlab

I wrote a Matlab code that involves doing a numeric calculation (relaxation), but it is quite slow. I learned of the possibility of using a mex file to run a C code and integrate it into Matlab, so I ...
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### CHOLMOD implementation

I am working on a domain decomposition code in C that uses CHOLMOD to approximate grid values for a PDE in each sub-domain. The issue I have is that the methods use Matrix Market format, which is not ...
317 views

### Linear solve using CHLOMOD in C

I am using the open-source CHLOMOD (as here http://faculty.cse.tamu.edu/davis/suitesparse.html) in order to solve a linear system Ax=b (performing A/b=x) in my domain decomposition code but I am ...
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### Open Source Linear Algebra Library

I am making a code in C that requires the equivalent of Matlab's '\' command for a linear system of the form AX=B where A is an NxN matrix and X, B are Nx1 vectors- i.e a code that performs X=A\B that ...
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### Array initialization in C

In this bit of code, the X and Y arrays should be identical but for some reason, that I CANNOT figure out for the life of me, X is always 1 rather than 0. I have tried initializing the whole array ...
282 views

### Error in MD simulation with Lennard-Jones potential in C, resulting in a lack of conservation of energy

I'm working on a MD simulation using the Lennard-Jones potential and the Velocity Verlet algorithm. The code compiles and runs, but the energy for each time step is not conserved; it decreases ...
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### Implementing velocity verlet for harmonic oscillator in C gives error wrt conservation of energy

I'm attempting to implement velocity Verlet with a harmonic oscillator in C, but I have some errors: Energy is not being conserved Energy oscillates much more than I would expect I believe the error ...
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### What PRNG function is this?

This is a 16-bit PRNG function, transcribed from assembly to C for easier reading: ...
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### PETSc - difference between PetscNew and PetscMalloc

I wonder what is the difference between both functions. In C++, the difference between new and malloc is easier: new allocates memory by calling the constructor. What about PETSc ? In the example, ...
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### PETCs - How should one initialize PetscRandom?

The documentation of PETSc shows an example of usage: ...