Please see the release notes in doc/devsim.pdf or at https://devsim.net for more detailed information about changes.

The following files were updated in the text documentation distributed with the software.

• CONTRIBUTING.md
• INSTALL.md
• README.md

The release version of this software is build against version 2 of the Intel MKL, which corresponds to the latest version of Anaconda Python. If you have issues running DEVSIM with this new version, please contact us at https://forum.devsim.org for assistance.

The submodule reference to SYMDIFF was updated due some changes to its build files. Some SYMDIFF build scripts in the DEVSIM repository were also updated.

The Intel Math Kernel Library now uses versioned library names. Binary releases are now updated against the latest versioned dll names from MKL available in the Anaconda Python distribution.

The rampbias function in the devsim.python_packages.ramp module has been fixed to properly reduce the bias when there is a convergence failure.

Fixed bug with transient_tr (trapezoidal) time integration method where the wrong sign was used to integrate previous time steps.

Fixed bug in the charge error calculation, which calculates the simulation result with that a forward difference projection.

Added testing/transient_rc.py test which compares simulation with analytic result for RC circuit.

Added set_initial_condition command to provide initial transient conditions based on current solution.

Added create_interface_from_nodes to make it possible to add interface from non-coincident pairs of nodes.

The maximum_error and maximum_divergence options where added to the solve command. If the absolute error of any iteration goes above maximum_error, the simulation stops with a convergence failure. The maximum_divergence is the maximum number of iterations that the simulator error may increase before stopping.

During the solve, circuit node and circuit solution information is no longer printed to the screen for the default verbosity level. In addition, the number of equations per device and region is no longer displayed at the start of the first iteration.

The code now supports newer versions of SuperLU. The release version is still using SuperLU 4.3 for the iterative solution method, and the Intel MKL Pardiso for the direct solve method.

The get_matrix_and_rhs command was not properly accepting the format parameter, and was always returning the same type.

The build scripts have been updated on all platforms to be less dependent on specific Python 3 versions.

An updated fedora build script has been added. It uses the system installed SuperLU as the direct solver.

Some out of date files (e.g. RELEASE, INSTALL, . . .) have been removed. The README.md has been updated and the INSTALL.md have been updated.

The variable_name option is no longer recognized for the devsim.contact_equation and devsim.interface_equation as it was not being used.

In most circumstances, the software now returns numerical data using the Python array class. This is more efficient than using standard lists, as it encapsulates a contiguous block of memory. More information about this class can be found at https://docs.python.org/3/library/array.html. The representation can be easily converted to lists and numpy arrays for efficient manipulation.

When accepting user input involving lists of homogenous data, such as set_node_values the user may enter data using either a list, string of bytes, or the array class. It may also be used to input numpy arrays or any other class with a tobytes method.

The get_matrix_and_rhs command has been added to assemble the static and dynamic matrices, as well as their right hand sides, based on the current state of the device being simulated. The format option is used to specify the sparse matrix format, which may be either in the compressed column or compressed row formats, csc or csr.

If the Newton iteration errors keep increasing for 20 iterations in a row, then the simulator stops. This limit was previously 5.

Elements written to the tecplot format in 2d and 3d have node orderings compatible with the element connectivity in visualization formats. Specifying the reorder=True option in get_element_node_list will result in node ordering compatible with meshing and visualization software.

The following inverse functions and their derivatives are now available in the model interpreter.

• erf_inv Inverse Error Function
• erfc_inv Inverse Complimentary Error Function
• derf_invdx Derivative of Inverse Error Function
• derfc_invdx Derivative of Complimentary Inverse Error Function

The Gauss-Fermi Integral, using Paasch's equations are now implemented.

• gfi Gauss-Fermi Integral
• dgfidx Derivative of Gauss-Fermi Integral
• igfi Inverse Gauss-Fermi Integral
• digfidx Derivative of Inverse Gauss-Fermi Integral

Each of these functions take two arguments, zeta and s. The derivatives with respect to the first argument are provided. Please see testing/GaussFermi.py for an example.

In extended precision mode, the following functions are now evaluated with full extended precision.

• Fermi
• dFermidx
• InvFermi
• dInvFermidx

The following double precision tests:

• testing/Fermi1.py Fermi Integral Test
• testing/GaussFermi.py Gauss Fermi Integral Test

Have extended precision variants:

• testing/Fermi1_float128.py
• testing/GaussFermi_float128.py

A new installation script is in the base directory of the package. It provides instructions of completing the installation to the python environment without having to set the PYTHONPATH environment variable. It notifies the user of missing components to finish the installation within an Anaconda or Miniconda environment.

To use the script, use the following command inside of the devsim directory.

    python install.py

The install script will write a file named lib/setup.py, which can be used to complete the installation using pip. The script provides instructions for the installation and deinstallation of devsim.

    INFO: Writing setup.py
    INFO:
    INFO: Please type the following command to install devsim:
    INFO: pip install -e lib
    INFO:
    INFO: To remove the file, type:
    INFO: pip uninstall devsim

The custom_equation command has been modified to require a third return value. This boolean value denotes whether the matrix entries should be row permutated or not. For the bulk equations this value should be True. For interface and contact boundary conditions, this value should be False.

It is now possible to replace an existing custom_equation.

The file examples/diode/diode_1d_custom.py demonstrates custom matrix assembly and can be directly compared to examples/diode/diode_1d.py.

The EdgeNodeVolume model is now available for the volume contained by an edge.

The contact_equation command now accepts 3 additional arguments.

• edge_volume_model
• volume_node0_model
• volume_node1_model

These options provide the ability to do volume integration on contact nodes.

The equation command has replaced the volume_model option with:

• volume_node0_model
• volume_node1_model

so that nodal quantities can be more localized.

More details are in the manual.

Windows 32 bit is no longer supported. Binary releases of the Visual Studio 2019 MSYS2/Mingw-w64 64-bit builds are still available online.

On Linux, the releases are now on Centos 7, as Centos 6 has reached its end of life on November 30, 2020.

The C++ standard has been raised to C++17.

The node indexes with the maximum error for each equation will be printed when debug_level is verbose.

devsim.set_parameter(name="debug_level", value="verbose")

These are printed as RelErrorNode and AbsErrorNode:

    Region: "gate"	RelError: 5.21531e-14	AbsError: 4.91520e+04
      Equation: "ElectronContinuityEquation"	RelError: 4.91520e-16	AbsError: 4.91520e+04
	RelErrorNode: 129	AbsErrorNode: 129

This information is also returned when using the info=True option on the solve command for each equation on each region of a device.

If the info flag is set to True on the solve command, the iteration information will be returned, and an exception for convergence will no longer be thrown. It is the responsibility of the caller to test the result of the solve command to see if the simulation converged. Other types of exceptions, such as floating point errors, will still result in a Python exception that needs to be caught.

Element assembly for calculation of current and charges from the device into the circuit equation are fixed. These tests are added:

• testing/cap_2d_edge.py
• testing/cap_2d_element.py
• testing/cap_3d_edge.py
• testing/cap_3d_element.py

The edge variant is using standard edge based assembly, and the element variant is using element-based assembly.

The element_pair_from_edge_model is available to calculate element edge components averaged onto each node of the element edge. This makes it possible to create an edge weighting scheme different from those used in element_from_edge_model.

Fixed issue where command option names where not always shown in the documentation.

The platform specific notes now clarify that any version of Python 3 (3.6 or higher) is supported.

• linux.txt
• windows.txt
• macos.txt

Fixed crash when evaluating element edge model in 3D.

Fixed potential error using delete_node_model and similar deletion commands.

Support for loading mesh files containing element edge data.

In transient mode, the convergence test was flawed so that the charge_error was the only convergence check required for convergence. The software now ensures all convergence criteria are met.

In the simple physics models, the sign for time-derivative terms was wrong for the electron and hole continuity equations. This affects small-signal and noise simulations. The example at examples/diode/ssac_diode.py was updated to reflect the change.

Fix build script issue for macOS on Travis CI, updated the compiler to g++-9.

Update Centos 6 build from devtoolset-6 to devtoolset-8.

Parameter info can be queried for getting version information. The file testing/info.py contains an example.

  python info.py
  {'copyright': 'Copyright © 2009-2020 DEVSIM LLC', 'direct_solver': 'mkl_pardiso', 'extended_precision': True, 'license': 'Apache License, Version 2.0', 'version': '1.4.6', 'website': 'https://devsim.org'}

The example examples/diode/gmsh_diode3d_float128.py provides an example where extended precision is enabled.

The Python scripts in the examples and testing directories have been reformatted to be more consistent with language standards.

Microsoft Windows 10 is supported and is now compiled using Microsoft Visual Studio 2019.

Microsoft Windows 7 is no longer supported, as Microsoft has dropped support as of January 14, 2020.

Support for reading meshes from Genius Device Simulator has been completely removed from DEVSIM.

• Platform Support:
  • An MSYS2/Mingw-w64 build is available for 64-bit Windows. This build, labeled devsim_msys_v1.4.5, enables the use of the 128-bit floating point precision already available on the macOS and Linux platforms.

• Bug Fixes:
  • Intermittent crash on Windows 10 at the end of the program
• CHANGES.md containing version changes in markdown format.
• Internal changes:
  • Regression system script refactored to Python.
  • Refactor threading code using C++11 functions
  • Refactor timing functions for verbose mode using C++11 functions.
  • Refactor FPE detection code to C++11 standard.