Code in this repository implements finite differences method for solution of Boltzmann equation for electron transport in two dimensional semiconductor super lattices. For reference see this article http://arxiv.org/abs/1401.6047 that contains mathematical model for this system and description of the paramaters. It contains several implementations. Two implementations in targeted to common CPU. One single threaded (bin/boltzmann_c_solver) and another one uses naive OpenMP (bin/boltzmann_openmp_solver). Other implementations are in CUDA and where tested on GTX680 (bin/boltzmann_solver). They are distinguished by different versions of kernel. To activate one or another kernel they have to be re-complied with environment variable BLTZM_KERNEL indicated kernel version. BLTZM_KERNEL may take one of the following values

• 1 - One thread per lattice point.
• 2 - One thread per lattice point. Uses shared memory.

In all following kernels each thread computes lattice values for each n.

• 310 - One thread per n.
• 311 - -//- and removed divergent flows.
• 321 - -//- and loops unrolled twice.
• 341 - -//- and loops unrolled four times.
• 342 - --------------//---------------- and elements partially reused.
• 4 - Loops are staggered and elemenets reused. Not unrolled.

Following parameters can be specified when executing boltzmann_solver. All parameters valuess are passed through use '=' sign. For example display=77

• display - indicates type of the output generated. Possible values are

  • 4 - compute instantaneous and averaged over external a/c emf. period drift velocities and absorption. Output file will contain detailed description of each field.

  • 7 - generate sequence of frame data files (files frame%08d.data) starting from time 'frame-start', which can be used to create movie sequences.

  • 8 - at the end of simulation generate single shot frame data file frame.data

  • 77 - similar to case of display=7 but instead of frame data produce output similar to display=4 containing time evolution of instantaneous drift velocities etc.

• n-harmonics - Maximum number of harmonics in expansion along the $\phi_x$ axis.

• PhiYmin - $\phi_y$ region is infinite, but to be able to numerically solve this problem we have to limit it to values from PhiYmin to PhiYmax

• PhiYmax - $\phi_y$ region is infinite, but to be able to numerically solve this problem we have to limit it to values from PhiYmin to PhiYmax

• t-max - computation runs from time t=0 to (t-max)+2*PI/omega

• frame-start - if you are making movie (display=7) frame data (files frame%08d.data) files start generating from time 'frame-start'

• dt - time step

• g-grid - number of cells alone the $\phi_y$ axis, with step size (PhiYmax - PhiYmin)/g-grid

• quiet - suppress progress output

• device - if you have more that one video card you may choose a specific one to run on by using this parameter, they are numbered starting from 0 (default value)

• o - output file. You can also use '+' sign to append to the existing file, like so o=+output.data

Following parameters have exact corresponance in http://arxiv.org/abs/1401.6047 Here we are showing to what LaTeX source each one corresponds to

• E_dc - corresponds to $E_{dc}$

• E_omega - corresponds to $E_{\omega}$

• omega - corresponds to $\omega$

• mu - corresponds to $\m$

• alpha - corresponds to $\alpha$

• B - corresponds to $B$