# Questions tagged [fortran]

Fortran is a general purpose programming language widely used by the scientific computing community.

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### How to use LAPACK function (DGELSY) in Fortran

I am trying to use Least Squares Minimization to solve a the matrix problem: b = A*x for x. The system is overdetermined, and A is a dense matrix. In the LAPACK library, I believe the routine DGELSY ...
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### Second derivative using Fornberg finite difference method

I have some discrete data, non-equispaced in x, y=f(x). I want to use a numerical finite difference method to calculate the second derivatives of y, at some point. I am using the Fornberg method, ...
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### Gaussian Elimination Using Fortran [closed]

I developed the code below for performing gaussian elimination in order to evaluate the determinant of a matrix: ...
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### Access PETSc data in totalview?

Is it possible to view the data stored in the various PETSc data types from within totalview? Ordinarily, PETSc types are integers which act as pointers to the actual data (obviously my understanding ...
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### LAPACK equivalent on c++ , which is the best one? [duplicate]

I am following a course of computational material physics. The professor uses fortran to code and uses lapack to solve eigenvalue problems. So far I just know c++. There is an equivalent library that ...
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### A robust algorithm to sort a non-convex polygon vertices

Let v_{0},...,v_{N-1} be N points in a Cartesian xy plane defining the vertices of closed polygon (i.e. v_{N} = v_{0}). Let P_{0}...
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### Compute outward normal and surface area for 8 noded brick element in FEA

I have a cube which is divided into 8 small cubes by bisecting each edge, I am trying to find out the surface area of each of the faces and the corresponding outward normals for them. This operation ...
174 views

### How write a integration loop in fortran, leapfrog scheme to solvind PDE (advection)?

I want to resolve numerically this equation using of difference finite method with Leapfrog Scheme $$\frac{\partial{u}}{\partial t}+ v \frac{\partial{u}}{\partial x}= 0$$ I'm trying to write a code ...
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### Analytical testing/quality control for scientific software in professional setting

I am charged with maintaining a buildserver on Teamcity which is meant to test our in house FE software. Currently our test suite consists of a list of benchmarks which run every time a commit is made ...
127 views

### Compute bilinear form with LAPACK

I need to compute a bilinear form for a set of left and right vectors $$w_k = \sum_{i,j} V_{ik}^*A_{ij}U_{jk},$$ where $A_{ij}\in\mathbb{R}$ and $U_{jk}, V_{ik} \in \mathbb{C}$ (Assume that all the ...
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### Why there are people that still prefer fortran 77 over new versions?

I am reading some notes from a course in numerical analysis for physical sciences and it is my impression that there are still people that prefer Fortran 77 over new version due to the implicit ...
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### How to compare runtimes of two algorithms in a reproducible way

I am solving one relatively simple problem with two different algorithm: one which uses brute force while the other is optimized. For a variety of reasons I actually cannot show the codes here but I ...
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### efficient MPI collective non-blocking communication

I am facing a problem with MPI (Fortran). I have a really big matrix at each node and they differ at different nodes. At some point of my calculations, each node needs the matrix from all other nodes, ...
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### what is the best way to code a formula to reduce roundoff error

I have an expression like the following (anyway to input latex?), $$z^{m}\left( \ln\left(\frac{z}{z-1}\right)-\sum_{k=1}^m \frac{z^{-k}}{k} \right)$$ for m integer, z complex It seems if I code it ...
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### Solve $AX=B$ where $A$ is a skyline matrix

Solve a matrix equation of the type $AX=B$, where $A$ is an $n \times n$ symmetric matrix stored in the form of symmetric skyline matrix. With the solution given by Bill and some more research on ...
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### Skyline solver for AX=B where A is symmetric skyline matrix

I am looking for a simple subroutine in Fortran 90 (GNU Compiler) to solve linear equation of the type $AX=B$, where $A$ is an $n\times n$ symmetric matrix stored in the form of symmetric skyline ...
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### What do C, C++ and Java have that Fortran 2003 don't? [closed]

As you may know, Fortran is widely and longly (?) used in science. I've heard a lot of people saying that we natural scientists should all migrate to C++ or Java. I've seen people increasingly ...