17k 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 ...
8k views

### Profiling CFD code with Callgrind

I'm using Valgrind + Callgrind to profile a solver I have written. As the Valgrind user manual states, I've compiled my code with the debugging options for the compiler: "Without debugging info, ...
3k views

### Beating typical BLAS libraries matrix multiplication performance

A dull matrix multiplication algorithm where we use the formula $$C_{ij}=\sum_{k}A_{ik}B_{kj}$$ By literally following this in 3 loops we'll get a very slow program, because we don't utilize ...
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 ...
790 views

### Lua and Fortran (or Python) I/O

I am writing a global climate simulation software system. My idea is the following : At the top of everything, I interface to the OS using D, a very powerful language for compile time code generation....
994 views

### Profiling optimized C code using gprof

I have a simple C code with many function calls, which I profiled using gprof. ...
71 views

### What are some tips on developing a problem-specific ODE solver?

I have a small system of stiff ODEs describing a chemical reaction. The right-hand side is quite complicated, as well as the Jacobian. This equation will be solved many times with different initial ...
485 views

I have a problem with parallelization and the brownian dynamics (molecular dynamics) code that I am using. We have our own home-grown framework at the university, and recently we've made the change ...
4k 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 ...
307 views

### What is the underlying structure of scientific code performance?

Consider two computers with different hardware and software configurations. When running the exact same serial Navier-Stokes code on each platform it takes x and y time to execute one iteration for ...
960 views

### Is there any benefit to compiling LAPACK from source versus installing the prebuilt package from Ubuntu?

I know that ATLAS is able to optimize itself for the machine it is compiled on and thus maximum benefits are found by compiling from source. Is there any benefit to compiling LAPACK from source? It ...
281 views

### How do I get reliable timing data for time spent in function calls in my code?

This question is a follow-up to Fortran: Best way to time sections of your code?. If I want to time functions in my code, I know I could use gprof or kcachegrind. I also know that the results from ...
2k views

### What other method can be used to solve differential equations except ode functions in Matlab?

Recently I am taking advantage of the ode45, as well as ode23s, ode15s solvers in ...
I have to perform a [complex] basis transformation on a large number of [real] diagonal matrices:  \langle b_i | A | b_j \rangle = \sum_k \langle b_i | \bar{b}_k\rangle \langle\bar{b}_k | A | \bar{b}...