# Changelog#

## 1.x-Series#

### v1.8.1 : Bugfix ellipse#

2022-10-15

• Small improvements to the ellipse-function (and the CLI):

• The major and minor axis of the ellipse are new forced to be at least 1e-9.

• A radius of 0.0 provided through the CLI is now respected (was before overwritten).

• empymod is more verbose when using layered computations.

• Maintenance:

• Replace deprecated sphinx-panels with sphinx-design.

### v1.8.0 : Layered modelling#

2022-08-31

The simulation class takes new the parameters layered and layered_opts, where the default values are False and None, respectively. If layered=True, there will be no 3D computations. Instead, it will create a local layered (1D) model for each source-receiver pair, and compute the response using the semi-analytical code empymod (which needs to be installed manually, as it is a soft dependency). In this case an eventual gradient is computed using the finite-difference method, not the adjoint-state method, perturbing each layer slightly. The main purpose of these layered computations is for quick checks, QC, verifications, etc. Layered computation is also possible through the CLI, through the new flag -l or --layered, and a new section [layered] in the config file.

Other changes (many of them related to the above):

• Model instances have a new attribute exctract_1d, which returns a layered (1D) model, extracted from the 3D model according the provided parameters; see emg3d.models.Model.extract_1d.

• CLI takes new the boolean add_noise in the section [noise_opts] (default is True).

• Maps: New function ellipse_indices returning a boolean indicating which points fall within a general ellipse for the provided input parameters.

• Bug fixes, small improvements and maintenance

• Simulation.misfit returns an ndarray again instead of an DataArray (was erroneously changed in v1.2.1).

• Write json can now handle NumPy int/bool/float.

• A clean on a Simulation now removes correctly the weights.

• Capture error in jtvec if weight is complex NaN (should be real).

• Model: mapping can now be an already instantiated map (sort of undocumented).

• Cleaned-up the namespace by setting dir() explicitly.

• Replace pytest-flake8 by plain flake8.

• Moved all multiprocessing-related functions to _multiprocessing.py.

### v1.7.1 : Bugfix trimmed z-vector#

2022-08-02

• Meshing: Small fix to the automatic gridding from v1.5.0 (non-backwards compatible). A provided z-vector is new trimmed to the domain before the domain might be expanded due to the provided seasurface (which is as it was always intended, but not as it was implemented).

• Few small maintenance things in the meta files.

### v1.7.0 : CLI-clean#

2022-05-21

• CLI:

• New command-line argument --clean: If an existing simulation is loaded, setting clean will remove any existing computed data (fields, misfit, gradient, residuals, synthetic data) and replace the model with the currently provided one.

• New command-line argument --cache (or as parameter cache in the configuration file under [files]): Acts as a shortcut for --load --save using the same file name.

• Parameters for noise generation should new be provided under their own section [noise_opts]; providing them under [simulation] is deprecated and will be removed in v1.9.0.

• Simulation:

• 'all' is now the same as 'computed' in to_file and to_dict, meaning the grids are stored as well.

• Deprecation: The 'expand'-functionality in the gridding options is deprecated and will be removed in v1.9.0. A property-complete model has to be provided.

• Meshes: Bumped the change of the default value for center_on_edge from True to False to v1.9.0, coinciding with the above deprecations.

### v1.6.1 : Max offset#

2022-05-11

• Survey: add_noise takes new a max_offset argument; receivers responses at offsets greater than maximum offset are set to NaN (also available through the CLI).

2022-04-30

• Simulation: gradient, jvec, and jtvec new support triaxial anisotropy (also through the CLI). As a consequence, gradient and jtvec return an ndarray of shape (nx, ny, nz) (isotropic) or ({2;3}, nx, ny, nz) (VTI/HTI; triaxial), and jvec expects an ndarray of shape (nx, ny, nz) (isotropic) or ({1;2;3}, nx, ny, nz) (isotropic; VTI/HTI; triaxial).

### v1.5.0 : Meshing: center on edge#

2022-03-30

• Meshes:

• construct_mesh and origin_and_widths take a new variable center_on_edge: If True, the center is put on an edge, if False, it is put at the cell center. Status quo is True, but the default will change to False in v1.7.0. If not set, it will currently raise a FutureWarning making the user aware of the change. Setting center_on_edge explicitly will suppress the warning.

• Constructed grids through construct_mesh and origin_and_widths with a defined seasurface might slightly change due to some improvements and refactoring in the course of the above changes to the center. The changes should not be severe.

• Simulation:

• gradient: Changed slightly to use the proper adjoint (changed only if the computational grids differ from the inversion grid; requires discretize).

• jvec: Adjusted to work for any mapping, not only conductivity, and also with adaptive gridding. It expects new a Fortran-ordered vector with the shape of the model (or a vector of that size). Gently reminder that the functions gradient, jvec, and jtvec are still considered experimental, and might change.

• New optional keyword tqdm_opts. With False you can switch off the progress bars. Alternatively one can provide a dict, which is forwarded to tqdm.

• CLI:

• Expose mean_noise and ntype, in addition to min_offset, to the CLI (for adding noise); also plain (for solver), and center_on_edge (for gridding options).

### v1.4.0 : Meshing: improve vector#

2022-02-09

• Meshes: Non-backwards compatible changes in construct_mesh (origin_and_widths; estimate_gridding_options) when providing vector’s (implemented non-backwards compatible as the old rules were not intuitive nor logic; previous meshes can still be obtained, mostly, by setting the parameters carefully).

• Priority-order changed to domain > distance > vector (before it was domain > vector > distance).

• A provided vector is new trimmed to the corresponding domain if it is larger than a also provided domain (from domain or distance); trimmed at the first point where vector <= domain[0], vector >= domain[1].

• A vector can new also be smaller than the defined domain, and the domain is then filled according to the normal rules; the last cell of vector in each direction is taken as starting width for the expansion.

• Bugfixes and maintenance:

• Removed functions and modules that were deprecated in v1.2.1.

• Fixed kwargs-error when adding add_noise explicitly to Simulation.compute().

• Python 3.10 added to tests; Python 3.7 tests reduced to minimum.

### v1.3.2 : Bugfix CLI-select#

2021-12-01

CLI: Add remove_empty to parameter file; set to False by default (pre-v1.3.1 behaviour, and therefore backwards compatible).

### v1.3.1 : Select: remove empty pairs#

2021-11-20

• Survey.select removes now empty source-receiver-frequency pairs. If you want the old behaviour set remove_empty=False.

• Maintenance: Added a cron to GHA; 20th of every month at 14:14.

### v1.3.0 : File-based computations#

2021-10-27

• electrodes:

• New source TxMagneticPoint (requires discretize; mainly used as adjoint source for magnetic receivers; does not work in the presence of magnetic permeabilities in the vicinity of the source).

• Both receivers (Rx{Electric;Magnetic}Point) can now produce their proper adjoint (thanks to @sgkang!).

• Changes in Simulation and parallel execution.

• Parallel computation is not sharing the simulation any longer.

• Parallel computation can new be done both file-based or all in memory. The new possibility for file-based computation should make it possible to compute responses for any amount of source-frequency pairs. See parameter file_dir in the Simulation class (or corresponding parameter in the CLI parameter file).

• get_model and get_hfield are now done on the fly, they are not stored in a dict; simulation._dict_model and simulation._dict_hfield do not exist any longer.

• New methods jvec (sensitivity times a vector) and jtvec (sensitivity transpose times a vector). These methods are currently experimental; documentation and examples are lacking behind.

• Various small things:

• Models and Fields return itself (not a copy) when the grid provided to interpolate_to_grid is the same as the current one.

### v1.2.1 : Remove optimize & bug fix#

2021-08-22

• io: Adjustment so that hdf5 tracks the order of dicts.

• simulations:

• Adjust printing: correct simulation results for adjusted solver printing levels; default solver verbosity is new 1; log can now be overwritten in solver_opts (mainly for debugging).

• Functions moved out of simulations: expand_grid_model moved to models and estimate_gridding_options to meshes. The availability of these functions through simulations will be removed in v1.4.0.

• optimize: the module is deprecated and will be removed in v1.4.0. The two functions optimize.{misfit;gradient} are embedded directly in Simulation.{misfit;gradient}.

### v1.2.0 : White noise#

2021-07-27

• CLI:

• New parameters save and load to save and load an entire simulation. In the parameter file, they are under [files]; on the command line, they are available as --save and --load; they are followed by the filename including its path and suffix. (In turn, the parameter store_simulation was removed.)

• simulations.Simulation:

• Warns if the gradient is called, but receiver_interpolation is not 'linear'.

• Slightly changed the added noise in compute(observed=True): It uses new the survey.add_noise attribute. There is new a flag to set if noise should be added or not (add_noise), and if the amplitudes should be chopped or not (min_amplitude). Also note that the added noise is new white noise with constant amplitude and random phase.

• surveys:

• New function random_noise, which can be used to create random noise in different ways. The default noise is white noise, hence constant amplitude with random phase. (This is different to before, where random Gaussian noise was added separately to the real and imaginary part.) For the random noise it requires new at least NumPy 1.17.0.

• New attribute Survey.add_noise, which uses under the hood above function.

• A Survey can new be instantiated without receivers by setting receivers to None. This is useful if one is only interested in forward modelling the entire fields. In this case, the related data object and the noise floor and relative error have no meaning. Also, in conjunction with a Simulation, the misfit and the gradient will be zero.

• Various:

• All emg3d-warnings (not solver warnings) are now set to 'always', and corresponding print statements were removed.

• Simplified (unified) _edge_curl_factor (private fct).

2021-06-30

This release contains, besides the usual small bugfixes, typos, and small improvements, an important fix for optimize.gradient. Keep in mind that while the forward modelling is regarded as stable, the optimize module is still work in progress.

The fixes with regard to optimize.gradient ensure that the gradient is indeed using the proper adjoint to back-propagate the field. This is currently only given for electric receivers, not yet for magnetic receivers. These improvement happened mainly thanks to the help of Seogi (@sgkang).

The changes in more detail:

• fields:

• get_receiver has a new keyword method, which can be 'cubic' or 'linear'; default is the former, which is the same behaviour as before. However, if you want to compute the gradient, you should set it to 'linear' in your Simulation parameters. Otherwise the adjoint-state gradient will not exactly be the adjoint state.

• get_source_field returns new the real-valued, frequency-independent source vector if frequency=None.

• get_source_field uses the adjoint of trilinear interpolation for point sources (new). For dipoles and wires it the source is distributed onto the cells as fraction of the source length (as before).

• electrodes: Re-introduced the point source as TxElectricPoint.

• simulations.Simulation:

• New keyword receiver_interpolation, which corresponds to the method in get_receiver (see above). Cubic is more precise. However, if you are interested in the gradient, you need to choose linear interpolation at the moment, as the point source is the adjoint of linear interpolation. To be the proper adjoint for the gradient the receiver has to be interpolated linearly too.

• If gridding is 'same' or 'input', it checks now if the provided grid is a sensible grid for emg3d; if not, it throws a warning.

• meshes: New function check_grid to verify if a given grid is good for emg3d.

• optimize.gradient: Changed order when going from computational grid to inversion grid. Changing the grids at the field stage (cubic interpolation) seems to be better than changing at the cell-averaged stage:

New: field_comp -> field_inv -> cells_inv
Old: field_comp -> cells_comp -> cells_inv

• cli: Uses now by default linear receiver interpolation if the gradient is wanted (new), otherwise it uses cubic interpolation (as before). The new keyword receiver_interpolation of the simulation can be set in the parameter file, which overwrites the described default behaviour.

### v1.0.0 : Stable API#

2021-05-28

Here it is, three months of hard labour lead to v1.0.0!

There are _many_ changes, and they are listed below for each module.

Your existing code will break, and I apologize for it. Please do not hesitate to get in touch if you have troubles updating your code.

API: With version 1.0 the API becomes stable and you can expect that your code will work fine for the duration of emg3d v1.x.

• Removed all deprecated features.

• Reduced top namespace to principal functions; get_receiver is not in the top namespace any longer. It is advised to use directly the field method: field.get_receiver.

• Moved emsig.github.io to emsig.xyz and emsig.readthedocs.io to emg3d.emsig.xyz.

• Changed principal repo branch from master to main.

#### Detailed changes by module#

CLI

• Because frequencies are now dicts as well in a Survey they have to be named by their key instead of their value when selecting data in the parameter file.

• Entire configuration is now added to the log file.

Core

• restrict_weights: New signature.

Electrodes

• New module containing all sources and receivers. Currently implemented are TxElectricDipole, TxMagneticDipole, TxElectricWire, RxElectricPoint, and RxMagneticPoint.

• New class TxElectricWire for an arbitrary electric wire.

• Receivers can be defined in absolute coordinates, or in coordinates relative to source position if they move with the source. Latter makes only sense within a Survey/Simulation.

• dip is new called elevation to make it clear that it is the angle positive upwards (anticlockwise from the horizontal plane).

• Bugfix of the loop area for a magnetic dipole (the area was previously wrong except for dipoles of length of 1).

• Zero source strength does no longer mean “normalized”, it means zero strength (hence no source).

• Besides the sources and receivers it contains utilities how to move electrodes in the coordinate system (e.g., rotation).

Fields

• fields.Field:

• Is not a subclassed ndarray any longer; with all its advantages and disadvantages. E.g., operations on Field are not possible any longer and have to be carried out on Field.field. However, it should be easier to maintain and expand in the future.

• New signature.

• Knows new its grid. As a consequence, all functions that required previously the grid and the field require new only the field; e.g., emg3d.fields.get_receiver.

• Has no property ensure_pec any longer, it is ensured directly in solver.prolongation.

• Has new the methods interpolate_to_grid and get_receiver.

• Renamed parameters in all functions:

• src to source;

• freq to frequency;

• rec to receiver.

• Removed functions and classes:

• SourceField; it is just a regular Field now;

• get_receiver (the name still exists, but it is now what was before fields.get_receiver_response).

• Renamed functions and classes (both do not take a grid any longer):

• get_h_field to get_magnetic_field;

• fields.get_receiver_response to fields.get_receiver.

I/O

Maps

• Changed function and class names:

• _Map to BaseMap;

• grid2grid to interpolate (new signature);

• edges2cellaverages to interp_edges_to_vol_averages (new signature);

• volume_average to interp_volume_average (new signature);

• interp3d to interp_spline_3d (new signature).

• maps.interpolate:

• Can now be used to interpolate values living on a grid to another grid or to points defined either by a tuple or by an ndarray.

• The implemented interpolation methods are ‘nearest’ (new), ‘linear’, ‘cubic’, and ‘volume’. Volume averaging (‘volume’) only works for grid-to-grid interpolations, not for grid-to-points interpolations.

• Does not accept entire fields any longer. Entire fields can be mapped with their own field.interpolate_to_grid method.

• Maps cannot be (de-)serialized any longer ({to;from_dict}); simply store its name, which can be provided to models.Model.

• Function rotation should be used for anything involving angles to use the defined coordinate system consistently.

Meshes

• Changed function and class names:

• _TensorMesh to BaseMesh;

• min_cell_width to cell_width.

• get_origin_widths to origin_and_widths (has new finer loops to fine grid sizes than before).

• meshes.BaseMesh:

• Reduced to the attributes origin, h, shape_{cells;nodes}, n_{cells;edges;faces}, n_{edges;faces}_{x;y;z}, {nodes;cell_centers}_{x;y;z}, shape_{edges;faces}_{x;y;z}, and cell_volumes. These are the only required attributes for emg3d.

• meshes.construct_mesh: domain, vector, distance, stretching, min_width_limits, and min_width_pps can now also be provided as a dict containing the three keys '{x;y;z}'.

• meshes.skin_depth takes new mu_r instead of mu.

• good_mg_cell_nr: max_prime is new max_lowest, as it could also be, e.g., 9, which is not a prime.

Models

• models.Model:

• Knows new its grid. As a consequence, all the functions that used to require the grid and the model require new only the model; e.g., emg3d.solver.solve or emg3d.fields.get_magnetic_field.

• If property_y or property_z are not set they return now None, not property_x.

• If a float is provided for a property it is new expanded to the shape of the model, and not kept as a float.

• Has to be initiated with all desired properties; it cannot be changed afterwards. E.g., if it was initiated without electric permittivity, it cannot be added afterwards. However, it can be initiated with dummy values and adjusted later.

• Renamed interpolate2grid to interpolate_to_grid.

• models.VolumeModel: Does not take a grid any longer.

Simulations

• Simulation:

• Works new for electric and magnetic dipole sources as well as electric wire sources; electric and magnetic point receivers.

• Works now as well for surveys that contain receivers which are positioned relatively to the source.

• New signature: no grid any longer, name is new an optional keyword parameter, new optional keyword parameter info.

• Method get_sfield is removed.

• expand_grid_model and estimate_gridding_opts have new signatures and do not take a grid any longer.

Solver

• solver.solve:

• New signature: no grid any longer; efield and cycle are moved to keyword arguments.

• The defaults for sslsolver, semicoarsening, and linerelaxation is new True (before it was False). This is not necessarily the fastest setting, but generally the most robust setting.

• New keyword parameter plain, which is by default False. If it is set to True it uses plain multigrid, hence sslsolver=False, semicoarsening=False, and linerelaxation=False, unless these parameters were set to anything different than True.

• Some verbosity levels changed (for consistency reasons throughout emg3d). The new levels are [old levels in brackets]:

• -1: Nothing [0]

• 0: Warnings [1]

• 1: One-liner at the end [2]

• 2: One-liner (dynamically updated) [-1]

• 3: Runtime and information about the method [same]

• 4: Additional information for each MG-cycle [same]

• 5: Everything (slower due to additional error computations) [same]

Level three updates now dynamically, just as level 2.

• solve_source(): New function, a shortcut for solve(). It takes a source and a frequency instead of a sfield, gets the sfield internally, and forwards everything to solver.solve.

• multigrid, krylov, smoothing, restriction, prolongation, residual, RegularGridProlongator: New signature, mainly not taking a grid any longer.

Surveys

• Survey:

• frequencies is new a dict just like sources and receivers.

• sources and receivers must be tuples or dicts; lists are no longer permitted. For this, the module surveys has new convenience functions txrx_coordinates_to_dict and txrx_lists_to_dict.

• Has no attribute observed any longer; access it just like any other data through Survey.data.observed.

• rec_coords and src_coords attributes changed to the methods receiver_coordinates and source_coordinates. receiver_coordinates takes an optional source key. For relatively located receivers, it returns by default all positions of this receiver for all source position. If a source-key is provided it only returns the receiver position for this source. This does not affect absolutely positioned receivers.

• Has no attribute rec_types any longer.

• name is new optional.

• New optional keywords date and info.

• noise_floor and relative_error are new stored as data array if they are not floats.

• The keyword fixed has been dropped. To simulate fixed surveys define the receivers with a relative offset to the source, instead of absolute coordinates.

• data can be a dict containing many data set.

• Automatic key names start now with 1 and have a hyphen between the prefix and the number; they also contain the abbreviated electrode name. E.g., Tx0 becomes TxED-1 or TxMD-1 or TxEW-1. Similar, Rx9 becomes RxEP-10 or RxMp-10, and f0 becomes f-1.

• Survey.size is now the total number, Survey.count is the count of the data that actually has non-NaN values.

• Now completely functional for receivers which are positioned relatively to the source.

• New functions txrx_coordinates_to_dict and txrx_lists_to_dict to collocate many sources or receivers into dicts (also frequencies_to_dict).

• Dipole: Replaced by the new source and receiver classes in the new module electrodes.

Time

• Moved Fourier from emg3d.utils to its own module emg3d.time.

• Renamed parameters:

• freq_req to freq_required;

• freq_calc to freq_compute;

• freq_calc_i to ifreq_compute;

• freq_inp to input_freq;

• freq_extrapolate_i to ifreq_extrapolate;

• freq_interpolate_i to ifreq_interpolate;

Utils

• Renamed Time to Timer.

• Moved Fourier to its own module emg3d.time.Fourier.

• _process_map new avoids concurrent.futures if max_workers<2.

## 0.x-Series#

### v0.17.0 : Magnetics in Simulation#

2021-03-03

• Simulation:

• Sources and receivers can now be magnetic, also for the adjoint-state gradient (unit loops, not yet arbitrarily loops).

• fields.get_source_field:

• The recommended way to use get_source_field is new to provide a Tx*-source instance.

• The msrc argument introduced in v0.16.0 is renamed to electric, and has the opposite meaning. If True, the source is electric, if False, the source is magnetic. This was made to streamline the meaning with the meaning given in surveys.Dipole. The old parameter msrc is deprecated and will be removed. Warning, if msrc was provided as positional argument instead of as keyword argument it will now be taken as electric, with the opposite meaning (backwards incompatible).

• The magnetic source was corrected and has the opposite sign now (factor -1; backwards incompatible).

• Bug fixes:

• Simulation: Stop overwriting synthetic data if provided in the survey to a simulation.

• CLI: Removed configuration info from output data; caused problems when storing to h5. This has to be resolved with properly addressing the io stuff. Currently only stores the data selection to output data.

### v0.16.1 : Verbosity & Logging#

2021-02-09

• Solve has a new keyword log, which enables to log the solver messages in the returned info dictionary instead of printing them to screen. This is utilized in the CLI and in the Simulation class to log the solver info.

• Survey has a new attribute select, which returns a reduced survey containing the selected sources, receivers, and frequencies.

• CLI:

• Configuration info is added to output data.

• Checks now first if all required files and directories exist, and exits gracefully otherwise informing the user. (The default thrown Python errors would be good enough; but user of the CLI interface might not be familiar with Python, so it is better to throw a very simple, clear message.)

• Log is more verbose with regards to solver (rel. error, time, nr of it.).

• Dipole throws new an error instead of a warning if it received an unknown keyword.

• Various small things with regard to how things are logged or shown on screen.

• Changed all DeprecationWarnings to FutureWarnings, meaning they will be removed in the next release.

• Bug fix with regards to data selection in the CLI; moved to Survey (see above).

### v0.16.0 : Arbitrarily shaped sources#

2021-01-13

• fields.get_source_field:

• Arbitrarily shaped sources (and therefore also loops) can now be created by providing a src that consists of x-, y-, and z-coordinates of all endpoints of the individual segments.

• Simple “magnetic dipole” sources can now be created by providing a point dipole ([x, y, z, azm, dip]) and set msrc=True. This will create a square loop of lengthxlength m perpendicular to the defined point dipole, hence simulating a magnetic source. Default length is 1 meter.

• Point dipoles and finite length dipoles were before treated differently. Point dipoles are new converted into finite length dipoles of provided length (default is 1 meter), and treated as finite length dipoles. This is backwards incompatible and means that the source field for point dipoles might not be exactly the same as before. However, in any properly set-up simulation this should have no influence on the result.

• Bugfix: Fix floating point issue when the smaller coordinate of a finite length dipole source was very close to a node, but not exactly. This is done by rounding the grid locations and source position, and the precision can be controlled via decimals; default is micrometer.

• fields: Values outside the grid in get_receiver and get_receiver_response are new set to NaN’s instead of zeroes. Additionally, the first and last values in each direction of the fields are ignored, to avoid effects form the boundary condition (receivers should not be placed that close to the boundary anyway).

• simulations:

• Within the automatic gridding the properties are estimated much more conservative now, if not provided: before the log10-average of the last slice in a given direction was used; now it uses the maximum resistivity. This is usually the air value for x/y and positive z. This is very conservative, but avoids that users use too small computational domains in the case of land and shallow marine surveys. The downside is that it heavily over-estimates the required domain in the deep marine case. However, slower but safe is better in this case.

• New method print_grids, which prints the info of all created grids. This is also used for logging in the CLI interface.

• maps: interp3d takes a new keyword cval, which is passed to map_coordinates.

### v0.15.3 : Move to EMSiG#

2020-12-09

Various small things, mostly related to the automatic meshing.

• New parameter distance for get_origin_widths, as an alternative for domain and vector: distance defines the survey domain as distance from the center. This is then also available in construct_mesh and Simulation, including the CLI.

• Removed precision from skin_depth, wavelength, min_cell_width; all in meshes. It caused problems for high frequencies.

• All data is stored in the Survey, not partly in Survey and partly in Simulation.

• Deprecated collect_classes in io.

• Expanded the what-parameter in the Simulation-class to include properties related to the gradient.

• Moved from github.com/empymod to github.com/emsig.

### v0.15.2 : Bugfix deploy II#

2020-12-04

• Fixing deploy script with GHA.

### v0.15.1 : Bugfix deploy#

2020-12-04

Small bugfix release, as v0.15.0 never got deployed.

• Fix CI deploy script.

• Makefile for the most common dev-tasks.

### v0.15.0 : discretize restructure#

2020-12-04

The package discretize went through a major restructuring with many name changes and consequent deprecations (see below for a list of affected mesh-properties for emg3d). This version updates emg3d to be compatible with discretize>=0.6.0 in the long run. It also means that emg3d will, from emg3d>=0.15.0 onwards, only work with discretize>=0.6.0.

Other notable changes:

• Moved from Travis CI to GitHub Actions.

The relevant aliases and deprecations for emg3d are (consult the release notes of discretize for all changes):

Aliases: Aliases (left) remain valid pointers to the new names (right).

• x0 => origin

• nC => n_cells

• vnC => shape_cells

• nN => n_nodes

• vnN => shape_nodes

• nE => n_edges

• nEx => n_edges_x

• nEy => n_edges_y

• nEz => n_edges_z

• vnE => n_edges_per_direction

• vnEx => shape_edges_x

• vnEy => shape_edges_y

• vnEz => shape_edges_z

Deprecations: Deprecated properties (left) raise a deprecation warning and will be removed in the future. Currently, they still work and point to the new names (right).

• hx => h[0]

• hy => h[1]

• hz => h[2]

• nCx => shape_cells[0]

• nCy => shape_cells[1]

• nCz => shape_cells[2]

• nNx => shape_nodes[0]

• nNy => shape_nodes[1]

• nNz => shape_nodes[2]

• vectorNx => nodes_x

• vectorNy => nodes_y

• vectorNz => nodes_z

• vectorCCx => cell_centers_x

• vectorCCy => cell_centers_y

• vectorCCz => cell_centers_z

• vol => cell_volumes

### v0.14.3 : Bug fix#

2020-11-19

• Bug fix for discretize>=0.6.0.

### v0.14.2 : Bug fix#

2020-11-18

• Bug fix for Windows affecting good_mg_cell_nr (int32 issue).

### v0.14.1 : Bug fix#

2020-11-14

• Fix for h5py>=3.0.

• Improved docs re automatic gridding.

### v0.14.0 : Automatic gridding#

2020-11-07

The simulation class comes new with an automatic gridding functionality, which should make it much easier to compute CSEM data. With that the entire optimization routine was improved too. See the API docs for more info of the relevant implementation.

• simulation:

• Simulation: New gridding options 'single', 'frequency' 'source', and 'both'; new default is 'single'.

• compute() takes a new argument, min_offset. If observed=True, it will add Gaussian random noise according to the standard deviation of the data; it will set receivers responses below the minimum offset to NaN.

• There is no longer a reference model.

• misfit and gradient can now handle observations with NaN’s.

• survey: A Survey has new attributes standard_error, noise_floor, and relative_error.

• optimize: Completely changed misfit and data-weighting to more sensible functions.

• cli:

• As a consequence of the changes the data_weight_opts got removed.

• New sections [data] to select the wanted data and [gridding_opts] for options of the automatic gridding.

• Section [simulation] has a new parameter min_offset (for creating observed data).

• Output has a new parameter n_observations if misfit or gradient were called, which is the number of observations that were used to compute the misfit.

• meshes:

• New functions construct_mesh, get_origin_widths, good_mg_cell_nr and other, smaller helper routines.

• Deprecated the old meshing routines get_hx_h0, get_cell_numbers, get_stretched_h, get_domain, get_hx; they will be removed in the future.

• Default of good_mg_cell_nr changed, and the documentation (and verbosity) with regards to «good» number of cells was improved.

• Bug fixes:

• maps: Fixed the mapping of the gradients (Conductivity is the only mapping that was not affected by this bug).

• Removed deprecated features:

• models.Model: Removed parameters res_{x;y;z}.

• io.save: Removed deprecated parameter backend.

• io.save: Removed default, file extension has to be provided.

### v0.13.0 : CLI#

2020-09-22

• New Module cli for command-line interaction:

The command-line interface can currently be used to forward model an entire Simulation, and also to compute the misfit of it with respect to some data and the gradient of the misfit function. See the section “CLI interface” in the documentation for more info.

Note that, while cli (v0.13.0) and optimize (v0.12.0) are implemented, they are still in development and are likely going to change throughout the next two minor releases or so.

• Other changes:

• solver: Changes in verbosity for emg3d.solve:

• New default verbosity is 1 (only warnings; before it was 2).

• Verbosities {-1;0;1} remain unchanged.

• Verbosities {2;3;4} => {3;4;5}.

• New verbosity 2: Only shows a one-liner at the end (plus warnings).

• survey and simulation: to_file and from_file have new a parameter name, to store and load with a particular name instead of the default survey/simulation (useful when storing, e.g., many surveys in one file).

• survey: stores new also the reference-data; different data (observed, reference) is contained in a data-dict when storing.

• simulation: takes new a verb parameter.

• optimize:

• Falls back to synthetic instead of observed now if reference not found.

• io: np.bool_ are converted back to bool when loading.

• Re-arrange, improve, and update documentation.

### v0.12.0 : Survey & Simulation#

2020-07-25

This is a big release with many new features, and unfortunately not completely backwards compatible. The main new features are the new Survey and Simulation classes, as well as some initial work for optimization (misfit, gradient). Also, a Model can now be a resistivity model, a conductivity model, or the logarithm (natural or base 10) therefore. Receivers can now be arbitrarily rotated, just as the sources. In addition to the existing soft-dependencies empymod, discretize, and h5py there are the new soft-dependencies xarray and tqm; discretize is now much tighter integrated. For the new survey and simulation classes xarray is a required dependency. However, the only hard dependency remain scipy and numba, if you use emg3d purely as a solver. Data reading and writing has new a JSON-backend, in addition to the existing HDF5 and NumPy-backends.

In more detail:

• Modules:

• surveys (new; requires xarray):

• Class surveys.Survey, which combines sources, receivers, and data.

• Class surveys.Dipole, which defines electric or magnetic point dipoles and finite length dipoles.

• simulations (new; requires xarray; soft-dependency tqdm):

• Class simulations.Simulation, which combines a survey with a model. A simulation computes the e-field (and h-field) asynchronously using concurrent.futures. This class will include automatic, source- and frequency-dependent gridding in the future. If tqdm is installed it displays a progress bar for the asynchronous computation. Note that the simulation class has still some limitations, consult the class documentation.

• models:

• Model instances take new the parameters property_{x;y;z} instead of res_{x;y;z}. The properties can be either resistivity, conductivity, or log_{e;10} thereof. What is actually provided has to be defined with the parameter mapping. By default, it remains resistivity, as it was until now. The keywords res_{x;y;z} are deprecated, but still accepted at the moment. The attributes model.res_{x;y;z} are still available too, but equally deprecated. However, it is no longer possible to assign values to these attributes, which is a backwards incompatible change.

• A model knows now how to interpolate itself from its grid to another grid (interpolate2grid).

• maps:

• New mappings for models.Model instances: The mappings take care of how to transform the investigation variable to conductivity and back, and how it affects its derivative.

• New interpolation routine edges2cellaverages.

• fields:

• Function get_receiver_response (new), which returns the response for arbitrarily rotated receivers.

• Improvements to Field and SourceField:

• _sval and _smu0 not stored any longer, derived from _freq.

• SourceField is now using the copy() and from_dict() from its parents class Field.

• io:

• File-format json (new), writes to a hierarchical, plain json file.

• Deprecated the use of backend, it uses the file extension of fname instead.

• This means .npz (instead of numpy), .h5 (instead of h5py), and new .json.

• New parameter collect_classes, which can be used to switch-on collection of the main classes in root-level dictionaries. By default, they are no longer collected (changed).

• meshes:

• meshes.TensorMesh new inherits from discretize if installed.

• Added __eq__ to models.TensorMesh to compare meshes.

• optimize (new)

• Functionalities related to inversion (data misfit, gradient, data weighting, and depth weighting). This module is in an early stage, and the API will likely change in the future. Current functions are misfit, gradient (using the adjoint-state method), and data_weighting. These functionalities are best accessed through the Simulation class.

• Dependencies:

• empymod is now a soft dependency (no longer a hard dependency), only required for utils.Fourier (time-domain modelling).

• Existing soft dependency discretize is now baked straight into meshes.

• New soft dependency xarray for the Survey class (and therefore also for the Simulation class and the optimize module).

• New soft dependency tqdm for nice progress bars in asynchronous computation.

• Deprecations and removals:

• Removed deprecated functions data_write and data_read.

• Removed all deprecated functions from utils.

• Miscellaneous:

• Re-organise API-docs.

• Much bookkeeping (improve error raising and checking; chaining errors, numpy types, etc).

### v0.11.0 : Refactor#

2020-05-05

Grand refactor with new internal layout. Mainly splitting-up utils into smaller bits. Most functionalities (old names) are currently retained in utils and it should be mostly backwards compatible for now, but they are deprecated and will eventually be removed. Some previously deprecated functions were removed, however.

• Removed deprecated functions:

• emg3d.solver.solver (use emg3d.solver.solve instead).

• Aliases of emg3d.io.data_write and emg3d.io.data_read in emg3d.utils.

• Changes:

• SourceField has now the same signature as Field (this might break your code if you called SourceField directly, with positional arguments, and not through get_source_field).

• More functions and classes in the top namespace.

• Replaced core.l2norm with scipy.linalg.norm, as SciPy 1.4 got the following PR: scipy/scipy#10397 (reason to raise minimum SciPy to 1.4).

• Increased minimum required versions of dependencies to

• scipy>=1.4.0 (raised from 1.1, see note above)

• empymod>=2.0.0 (no min requirement before)

• numba>=0.45.0 (raised from 0.40)

• New layout

• njitted -> core.

• utils split in fields, meshes, models, maps, and utils.

• Bugfixes:

• Fixed to_dict, from_dict, and copy for the SourceField.

• Fixed io for SourceField, that was not implemented properly.

### v0.10.1 : Zero Source#

2020-04-29

• Bug fixes:

• Checks now if provided source-field is zero, and exists gracefully if so, returning a zero electric field. Until now it failed with a division-by-zero error.

• Improvements:

• Warnings: If verb=1 it prints a warning in case it did not converge (it finished silently until now).

• Improvements to docs (figures-scaling; intersphinx).

• Adjust Fields.pha and Fields.amp in accordance with empymod v2: .pha and .amp are now methods; uses directly empymod.utils.EMArray.

• Adjust tests for empymod v2 (Fields, Fourier).

### v0.10.0 : Data persistence#

2020-03-25

• New:

• New functions emg3d.save and emg3d.load to save and load all sort of emg3d instances. The currently implemented backends are h5py for .h5-files (default, but requires h5py to be installed) and numpy for .npz-files.

• Classes emg3d.utils.Field, emg3d.utils.Model, and emg3d.utils.TensorMesh have new methods .copy(), .to_dict(), and .from_dict().

• emg3d.utils.Model: Possible to create new models by adding or subtracting existing models, and comparing two models (+, -, == and !=). New attributes shape and size.

• emg3d.utils.Model does not store the volume any longer (just vnC).

• Deprecations:

• Deprecated data_write and data_read.

• Internal and bug fixes:

• All I/O-related stuff moved to its own file io.py.

• Change from NUMBA_DISABLE_JIT to use py_func for testing and coverage.

• Bugfix: emg3d.njitted.restrict did not store the {x;y;z}-field if sc_dir was {4;5;6}, respectively.

### v0.9.2 : Complex sources#

2019-12-26

• Strength input for get_source_field can now be complex; it also stores now the source location and its strength and moment.

• get_receiver can now take entire Field instances, and returns in that case (fx, fy, fz) at receiver locations.

• Krylov subspace solvers:

• Solver now finishes in the middle of preconditioning cycles if tolerance is reached.

• Solver now aborts if solution diverges or stagnates also for the SSL solvers; it fails and returns a zero field.

• Removed gmres and lgmres from the supported SSL solvers; they do not work nice for this problem. Supported remain bicgstab (default), cgs, and gcrotmk.

• Various small things:

• New attribute Field.is_electric, so the field knows if it is electric or magnetic.

• New verb-possibility: verb=-1 is a continuously updated one-liner, ideal to monitor large sets of computations or in inversions.

• The returned info dictionary contains new keys:

• runtime_at_cycle: accumulated total runtime at each cycle;

• error_at_cycle: absolute error at each cycle.

• Simple __repr__ for TensorMesh, Model, Fourier, Time.

• Bugfixes:

• Related to get_hx_h0, data_write, printing in Fourier.

### v0.9.1 : VolumeModel#

2019-11-13

• New class VolumeModel; changes in Model:

• Model now only contains resistivity, magnetic permeability, and electric permittivity.

• VolumeModel contains the volume-averaged values eta and zeta; called from within emg3d.solver.solver.

• Full wave equation is enabled again, via epsilon_r; by default it is set to None, hence diffusive approximation.

• Model parameters are now internally stored as 1D arrays.

• An {isotropic, VTI, HTI} initiated model can be changed by providing the missing resistivities.

• Bugfix: Up and till version 0.8.1 there was a bug. If resistivity was set with slices, e.g., model.res[:, :, :5]=1e10, it DID NOT update the corresponding eta. This bug was unintentionally fixed in 0.9.0, but only realised now.

• Various:

• The log now lists the version of emg3d.

• PEP8: internal imports now use absolute paths instead of relative ones.

• Move from conda-channel prisae to conda-forge.

• Automatic deploy for PyPi and conda-forge.

### v0.9.0 : Fourier#

2019-11-07

• New routine:

• emg3d.utils.Fourier, a class to handle Fourier-transform related stuff for time-domain modelling. See the example notebooks for its usage.

• Utilities:

• Fields and returned receiver-arrays (EMArray) both have amplitude (.amp) and phase (.pha) attributes.

• Fields have attributes containing frequency-information (freq, smu0).

• New class SourceField; a subclass of Field, adding vector and v{x,y,z} attributes for the real valued source vectors.

• The Model is not frequency-dependent any longer and does NOT take a freq-parameter any more (currently it still takes it, but it is deprecated and will be removed in the future).

• data_write automatically removes _vol from TensorMesh instances and _eta_{x,y,z}, _zeta from Model instances. This makes the archives smaller, and they are not required, as they are simply reconstructed if needed.

• Internal changes:

• The multigrid method, as implemented, only works for the diffusive approximation. Nevertheless, we always used \sigma-i\omega\epsilon, hence a complex number. This is now changed and \epsilon set to 0, leaving only \sigma.

• Change time convention from exp(-iwt) to exp(iwt), as used in empymod and commonly in CSEM. Removed the parameter conjugate from the solver, to simplify.

• Change own private class variables from __ to _.

• res and mu_r are now checked to ensure they are >0; freq is checked to ensure !=0.

• New dependencies and maintenance:

• empymod is a new dependency.

• Travis now checks all the url’s in the documentation, so there should be no broken links down the road. (Check is allowed to fail, it is visual QC.)

• Bugfixes:

• Fixes to the setuptools_scm-implementation (MANIFEST.in).

### v0.8.1 : setuptools_scm#

2019-10-22

• Implement setuptools_scm for versioning (adds git hashes for dev-versions).

### v0.8.0 : Laplace#

2019-10-04

• Laplace-domain computation: By providing a negative freq-value to utils.get_source_field and utils.Model, the computation is carried out in the real Laplace domain s = freq instead of the complex frequency domain s = 2i*pi*freq.

• New meshing helper routines (particularly useful for transient modelling where frequency-dependent/adaptive meshes are inevitable):

• utils.get_hx_h0 to get cell widths and origin for given parameters including a few fixed interfaces (center plus two, e.g. top anomaly, sea-floor, and sea-surface).

• utils.get_cell_numbers to get good values of number of cells for given primes.

• Speed-up njitted.volume_average significantly thanks to Joe (@jcapriot).

• Bugfixes and other minor things:

• Abort if l2-norm is NaN (only works for MG).

• Workaround for the case where a sslsolver is used together with a provided initial efield.

• Changed parameter rho to res for consistency reasons in utils.get_domain.

• Changed parameter h_min to min_width for consistency reasons in utils.get_stretched_h.

### v0.7.1 : JOSS article#

2019-07-17

• Version of the JOSS article, https://doi.org/10.21105/joss.01463 .

• New function utils.grid2grid to move from one grid to another. Both functions (utils.get_receiver and utils.grid2grid) can be used for fields and model parameters (with or without extrapolation). They are very similar, the former taking coordinates (x, y, z) as new points, the latter one another TensorMesh instance.

• New jitted function njitted.volume_average for interpolation using the volume-average technique.

• New parameter conjugate in solver.solver to permit both Fourier transform conventions.

• Added exit_status and exit_message to info_dict.

• Add section Related ecosystem to documentation.

### v0.7.0 : H-field#

2019-07-05

• New routines:

• utils.get_h_field: Small routine to compute the magnetic field from the electric field using Faraday’s law.

• utils.get_receiver: Small wrapper to interpolate a field at receiver positions. Added 3D spline interpolation; is the new default.

• Re-implemented the possibility to define isotropic magnetic permeabilities in utils.Model. Magnetic permeability is not tri-axially included in the solver currently; however, it would not be too difficult to include if there is a need.

• CPU-graph added on top of RAM-graph.

• Expand utils.Field to work with pickle/shelve.

• Jit np.linalg.norm (njitted.l2norm).

• Use scooby (soft dependency) for versioning, rename Version to Report (backwards incompatible).

• Bug fixes:

• Small bugfix introduced in ebd2c9d5: sc_cycle and lr_cycle was not updated any longer at the end of a cycle (only affected sslsolver=True.

• Small bugfix in utils.get_hx.

### v0.6.2 : CPU & RAM#

2019-06-03

Further speed and memory improvements:

• Add CPU & RAM-page to documentation.

• Change loop-order from x-z-y to z-x-y in Gauss-Seidel smoothing with line relaxation in y-direction. Hence reversed lexicographical order. This results in a significant speed-up, as x is the fastest changing axis.

• Move total residual computation from solver.residual into njitted.amat_x.

• Simplifications in utils:

• Simplify utils.get_source_field.

• Simplify utils.Model.

• Removed unused timing-stuff from early development.

### v0.6.1 : Memory#

2019-05-28

Memory and speed improvements:

• Only compute residual and l2-norm when absolutely necessary.

• Inplace computations for np.conjugate in solver.solver and np.subtract in solver.residual.

### v0.6.0 : RegularGridInterpolator#

2019-05-26

• Replace scipy.interpolate.RegularGridInterpolator with a custom tailored version of it (class:emg3d.solver.RegularGridProlongator); results in twice as fast prolongation.

• Simplify the fine-grid computation in prolongation without using gridE*; memory friendlier.

• Submission to JOSS.

• Some major refactoring, particularly in solver.

• Removed discretize as hard dependency.

• Rename rdir and ldir (and related p*dir; *cycle) to the more descriptive sc_dir and lr_dir.

### v0.5.0 : Accept any grid size#

2019-05-01

• First open-source version.

• Include RTD, Travis, Coveralls, Codacy, and Zenodo. No benchmarks yet.

• Accepts now any grid size (warns if a bad grid size for MG is provided).

• Coarsens now to the lowest level of each dimension, not only to the coarsest level of the smallest dimension.

• Combined restrict_rx, restrict_ry, and restrict_rz to restrict.

• Improve speed by passing pre-allocated arrays to jitted functions.

• Store res_y, res_z and corresponding eta_y, eta_z only if res_y, res_z were provided in initial call to utils.model.

• Change zeta to v_mu_r.

• Include rudimentary TensorMesh-class in utils; removes hard dependency on discretize.

• Bugfix: Take a provided efield into account; don’t return if provided.

### v0.4.0 : Cholesky#

2019-03-29

• Use solve_chol for everything, remove solve_zlin.

• Moved mesh.py and some functionalities from solver.py into utils.py.

• New mesh-tools. Should move to discretize eventually.

• Improved source generation tool. Might also move to discretize.

• printversion is now included in utils.

• Many bug fixes.

• Lots of improvements to tests.

• Lots of improvements to documentation. Amongst other, moved docs from __init__.py into the docs rst.

2019-01-18

### v0.2.0 : Line relaxation#

2019-01-14

• Line relaxation option.

### v0.1.0 : Initial#

2018-12-28

• Standard multigrid with or without BiCGSTAB.

• Tri-axial anisotropy.

• Number of cells must be 2^n, and n has to be the same in the x-, y-, and z-directions.