Fortran is a general purpose programming language widely used by the scientific computing community.
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An Octree Code in Fortran
I am a new to scientific computing. I am looking for a Fortran ( preferably f90) implementation of an Octree.
My problem requires an Octree which divides my domain until there aren't more than some N ...
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votes
2answers
112 views
How does longer simulation time affect simulation results?
I have a transient flow and solute transport simulation running using a fortran code. The final solution time is 1 day. I need the output of hydraulic head for the output time of 0.5 day. I want to ...
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2answers
146 views
F2Py with allocatable and assumed shape arrays
I would like to use f2py with modern Fortran. In particular I'm trying to get the following basic example to work. This is the smallest useful example I could ...
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1answer
141 views
Effecient CFD programming techniques
I'm trying to make highly efficient CFD programming complex for solving combustion problems. I've finished writing core which realises mathematical model, and now I'm concerned about code performance. ...
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3answers
173 views
Fortran: Best way to time sections of your code?
Sometimes while optimizing code it is required to time certain portions of the code, I have been using the following for years but was wondering if there is a simpler/better way to do it?
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1answer
85 views
Memory management in time-domain simulation
I develop a parallel time-domain DAE simulation software using OpenMP and Fortran 2003. The main algorithm is:
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Local axis follows origin node rotation
I'd like to define a local axis (unit vectors l, m and n) which once defined follow the rotation of the origin node, i.e. regardless of the deformation the local axis should be basically the same as ...
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5answers
185 views
Evaluate the sum
I want to evaluate the sum $$\sum_{k=1}^\infty \left(\frac{i+1}{\sqrt{2}}\right)^k\cdot k^{-\alpha}$$ where $i=\sqrt{-1}$ and $\alpha\in[\frac{3}{4},1]$ with 8 digits accuracy.
If I am willing to ...
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0answers
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How to accurately decompose positive semidefinite matrix and use the lower triangular part in linear equations
I have $n$ arbitrary $p\times 1$ vectors $x_i$, and $p\times k$ matrices $A_i$, and $n$ $p \times p$ positive semidefinite matrices $S_i$, where some (often most) of the $S_i$'s are same (for example ...
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1answer
171 views
Grid mapping from an unstructured triangular mesh to a regular rectangular mesh
I am modeling fracture propagation using a 2-D dynamic unstructured grid. As the fracture propagates over time, the elements move accordingly. For a given time step, I would like to interpolate the ...
9
votes
2answers
356 views
Row major versus Column major layout of matrices
In programming dense matrix computations, is there any reason
to choose a row-major layout of the over the column-major layout?
I know that depending on the layout of the matrix chosen, we need to ...
6
votes
2answers
309 views
Memory usage in fortran when using an array of derived type with pointer
In this sample program I'm doing the same thing (at least I think so) in two different ways. I'm running this on my Linux pc and monitoring the memory usage with top. Using gfortran I find that in the ...
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1answer
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How to get sparse complex matrices from my code to PETSc efficiently
What is the most efficient way to get a complex sparse matrix from my Fortran code to PETSc? I understand that this is problem dependent, so I tried to give as many relevant details as possible below.
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1answer
548 views
Where is the bug in my fourth order Runge-Kutta method implementation?
I am trying to build a Runge-Kutta code to integrate the equations of motion for a simple harmonic oscillator. However, when I run the code, I only see first order improvement in the error as I ...
5
votes
3answers
278 views
How do I know if my code is being vectorized by the compiler?
As exemplified by Jed Brown's answer to Costs of lookups versus calculations, using vectorized vs non-vectorized floating point operations results in much faster code. Many modern compilers claim ...
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votes
4answers
729 views
Parallel Scientific Computation Software Development Language?
I want to develop a parallel scientific computation software from scratch. I want some thoughts on which language to start. The program involves reading/writing data to txt files and doing heavy ...
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3answers
4k views
How should I install a Fortran compiler on a Mac? (OS X 10.x, x >= 4)
Related question: State of the Mac OS in Scientific Computing and HPC
A significant number of software packages in computational science are written in Fortran, and Fortran isn't going away. A ...
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5answers
525 views
Are there open-source scientific libraries which use modern Fortran with OOP?
I've spent the last couple of months on coding a Fortran program for solving a particular PDE system (describes fluid flow/combustion). I tryed to use latest-standard Fortran and the new OOP ...
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5answers
451 views
Which package should I use to wrap Modern Fortran Code with Python?
I know of, and have used f2py2e to wrap some old Fortran 77 code, but my understanding is that it does not work with newer Fortran 95 code. I've researched what I should use, and have come across ...
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4answers
806 views
Is C slower than Fortran on the spectral norm shootout (using gcc, intel and other compilers)?
The conclusion here:
How much better are Fortran compilers really?
is that gfortran and gcc are as fast for simple code. So I wanted try something more complicated. I took the spectral norm shootout ...
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votes
3answers
501 views
Are DAXPY, DCOPY, DSCAL overkills?
I have implemented CG in FORTRAN by linking it to Intel MKL.
When there are statements like:
(Refer Wikipedia)
p=r;
x=x+alpha*p
r=r-alpha*Ap;
or similar ...
13
votes
4answers
475 views
How do I write dimensionally agnostic code?
I often find myself writing very similar code for one, two, and three dimensional versions of a given operation/algorithm. Maintaining all of these versions can become tedious. Simple code ...
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0answers
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Is there a tool out there that can generate interval extensions of Fortran (or C) functions by parsing Fortran (or C) code?
Case studies in my PhD thesis require that I have interval extensions of Fortran subroutines in CHEMKIN-II (apologies for the link; it's the best one I could find for a package no longer distributed ...
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votes
3answers
469 views
Matrix exponential of a real asymmetric matrix with Fortran 95 and LAPACK
I recently asked a question along the same lines for skew-Hermitian matrices. Inspired by the success of that question, and after banging my head against a wall for a couple of hours, I'm looking at ...
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3answers
415 views
Matrix exponential of a skew-Hermitian matrix with fortran 95 and LAPACK
I'm just getting tucked into fortran 95 for some quantum mechanics simulations. Honestly, I've been spoiled by Octave so I've taken matrix exponentiation for granted. Given a (small, $n\leq 36$) ...
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4answers
3k views
How much better are Fortran compilers really?
This question is an extension of two discussions that came up recently in the replies to "C++ vs Fortran for HPC". And it is a bit more of a challenge than a question...
One of the most often-heard ...
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2answers
234 views
Filtering a dataset to get a more uniform distribution for neural network training
I'm looking into using artificial neural networks (ANN) to predict the reaction rates in my fluid instead of solving the full system of stiff ODEs. Some people from my lab have already done some work ...
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votes
2answers
810 views
How to set double precision values in Fortran
Recently, I've encountered a bizarre problem with FORTRAN95. I initialized variables X and Y as follows:
X=1.0
Y=0.1
Later I add them together and print the ...
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votes
2answers
243 views
How do I compile a program that contains both MPI and OPENMP
I have a fortran 90 code that distributes blocks of computations (from a matrix) to multiple nodes in a cluster using MPI, but in each node, the for loops are executed in parallel using openmp. I ...
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11answers
4k views
C++ vs Fortran for HPC
In my computational science PhD program, we are working almost exclusively in C++ and Fortran. It seems like some professors prefer one over the other. I am wondering which one is 'better' or if one ...
8
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2answers
1k views
How to work with function pointers in Fortran in scientific programs
Here is a typical usage of function pointers in C. I would like to do something similar in Fortran. I have some ideas, but I would like to know if there is some canonical way to do so.
The function ...
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2answers
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Intel Fortran Compiler: tips on optimization at compilation
I will start with my personal experience in our lab. Back in the ifort 9 and 10 days, we used to be quite aggressive with the optimizations, compiling with -O3 and processor specific flags (-xW ...
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What makes Fortran fast?
Fortran has a special place in numerical programming. You can certainly make good and fast software in other languages, but Fortran keeps performing very well despite its age. Moreover, it's easier to ...
