This document was last updated on July 25 2018, for version 3.1.4

The Dplus Python API

The D+ Python API allows using the D+ backend from Python, instead of the ordinary D+ application.

The Python API works on both Windows and Linux.

Installation

Installing the Python API is done using PIP:

pip install dplus-api

The API was tested with Python 3.5 and newer. It may work with older versions of Python, although Python 2 is probably not supported.

Overview

Some notes:

Throughout the manual, code examples are given with filenames, such as “mystate.state”. To run the example code for yourself, these files must be located in the same directory as the script itself, or alternately the code can be modified to contain the full path of the file’s location.

Throughout the manual, we mention “state files”. A state file is a JavaScript Object Notation (JSON) format file (https://www.json.org/), which describes the parameter tree and calculation settings of the D+ computation.

It is unnecessary to write a state file yourself. State files can either be generated from within the python interface (with the function export_all_parameters), or created from the D+ GUI (by selecting File>Export All Parameters from within the D+ GUI).

The overall flow of the Python API is as follows:

  1. The data to be used for the calculation is built by the user in an instance of the CalculationInput class. CalculationInput is a child class of the class State, which represents a program state. A State includes both program preferences such as DomainPreferences, and a parameter tree composed of Models.
  2. The calculation input is then passed to a CalculationRunner class (either LocalRunner or WebRunner), and the calculation function is called (generate, generate_async, fit, or fit_async).
  3. The CalculationRunner class returns an instance of a CalculationResult class, either FitResult or GenerateResult.

Here is a very simple example of what this might look like in main.py:

from dplus.CalculationInput import CalculationInput
from dplus.CalculationRunner import LocalRunner

calc_data = CalculationInput.load_from_state_file("mystate.state")
runner = LocalRunner()
result = runner.generate(calc_data)
print(result.graph)

A detailed explanation of the class types and their usage follows.

CalculationRunner

There are two kinds of CalculationRunners, Local and Web.

The LocalRunner is intended for users who have the D+ executable files installed on their system. It takes two optional initialization arguments:

  • exe_directory is the folder location of the D+ executables. By default, its value is None. On Windows, a value of None will lead to the python interface searching the registry for an installed D+ on its own, but on linux the executable directory must be specified.
  • session_directory is the folder where the arguments for the calculation are stored, as well as the output results, Amplitude files, and protein data bank (PDB) files, from the C++ executable. By default, its value is None, and an automatically generated temporary folder will be used.
from dplus.CalculationRunner import LocalRunner

exe_dir = r"C:\Program Files\D+\bin"
sess_dir = r"sessions"
runner = LocalRunner(exe_dir, sess_dir)
#also possible:
#runner = LocalRunner()
#runner = LocalRunner(exe_dir)
#runner = LocalRunner(session_directory=sess_dir)

The WebRunner is intended for users accessing the D+ server. It takes two required initialization arguments, with no default values:

  • url is the address of the server.
  • token is the authentication token granting access to the server.
from dplus.CalculationRunner import WebRunner

url = r'http://localhost:8000/'
token = '4bb25edc45acd905775443f44eae'
runner = WebRunner(url, token)

Both runner classes have the same four methods:

generate(calc_data), generate_async(calc_data), fit(calc_data), and fit_async(calc_data).

All four methods take the same single argument, calc_data - an instance of a CalculationData class.

generate and fit return a CalculationResult.

generate_async and fit_async return a RunningJob.

When using generate or fit the program will wait until the call has finished and returned a result, before continuing. Their asynchronous counterparts (generate_async and fit_async) allow D+ calculations to be run in the background (for example, the user can call generate_async, tell the program to do other things, and then return and check if the computation is finished).

RunningJob

The user should not be initializing this class. When returned from an async function (generate_async or fit_async) in CalculationRunner, the user can use the following methods to interact with the RunningJob instance:

  • get_status(): get a JSON dictionary reporting the job’s current status
  • get_result(calc_data): get a CalculationResult. Requires a copy of the CalculationInput used to create the job. Should only be called when the job is completed. It is the user’s responsibility to verify job completion with get_status before calling.
  • abort(): end a currently running job
from dplus.CalculationInput import CalculationInput
from dplus.CalculationRunner import LocalRunner

 calc_data = CalculationInput.load_from_state_file("mystate.state")
 runner = LocalRunner()
 job = runner.generate_async(calc_data)
 start_time = datetime.datetime.now()
 status = job.get_status()
 while status['isRunning']:
     status = job.get_status()
     run_time = datetime.datetime.now() - start_time
     if run_time > datetime.timedelta(seconds=50):
         job.abort()
         raise TimeoutError("Job took too long")
 result = job.get_result(calc_data)

State

The state class contains an instance of each of three classes: DomainPreferences, FittingPreferences, and Domain. They are described in the upcoming sections.

It has the methods:

  • get_model: get a model by either its name or its pointer, model_ptr.
  • get_models_by_type: returns a list of Models with a given type_name, for example, UniformHollowCylinder.
  • get_mutable_params: returns a list of Parameters in the state class, whose property mutable is True.
  • get_mutable_parameter_values: returns a list of floats, matching the values of the mutable parameters.
  • set_mutable_parameter_values: given a list of floats, sets the mutable parameters of the State (in the order given by get_mutable_parameter_values).
  • export_all_parameters: given a filename, will save the calculation State to that file.
  • add_model: a convenience function to help add models to the parameter tree of a ‘State’. It receives the model and optionally a population index (default 0), and will insert that model into the population.
  • add_amplitude: a convenience function specifically for adding instances of the Amplitude class, described below. It creates an instance of an AMP class with the filename of the Amplitude. Then, in addition to calling add_model with that AMP instance, it also changes the DomainPreferences of the State (specifically, grid_size, q_max, and use_grid), to match the properties of the Amplitude. It returns the ‘AMP’ instance it created.

State, and every class and sub class contained within state (for example: preferences, models, parameters), all have the functions load_from_dictionary and serialize.

load_from_dictionary sets the values of the various fields within a class to match those contained within a suitable dictionary. It can behave recursively as necessary, for example, with a model that has children.

serialize saves the contents of a class to a dictionary. Note that there may be additional fields in the dictionary beyond those described in this document, because some defunct (outdated, irrelevant, or not-yet-implemented) fields are still saved in the serialized dictionary.

DomainPreferences

The DomainPreferences class contains properties that are copied from the D+ interface. Their usage is explained in the D+ documentation.

We create a new instance of DomainPreferences by calling the python initialization function:

dom_pref= DomainPreferences()

There are no arguments given to the initialization function, and all the properties are set to default values:

Property Name Default Value Allowed values
signal_file "" “”, or a valid file location
convergence 0.001  
grid_size 100 Even integer greater than 20
orientation_iterations 100  
orientation_method "Monte Carlo (Mersenne Twister)" "Monte Carlo (Mersenne Twister)", "Adaptive (VEGAS) Monte Carlo", "Adaptive Gauss Kronrod"
use_grid False True, False
q_max 7.5 Positive number. If signal file is provided, must match highest x value

Any property can then be easily changed, for example,

dom_pref.q_max= 10

If the user tries to set a property to an invalid value (for example, setting q_max to something other than a positive number) they will get an error.

If a signal file is provided, the value of q_max will automatically be set to the highest x value in the signal file.

Fitting Preferences

The FittingPreferences class contains properties that are copied from the D+ interface. Their usage is explained in the D+ documentation.

We create a new instance of FittingPreferences by calling the python initialization function:

fit_pref= FittingPreferences()

There are no arguments given to the initialization function, and all the properties are set to default values:

Property Name Default Value Allowed Values Required when
convergence 0.1 Positive numbers  
der_eps 0.1 Positive numbers  
fitting_iterations 20 Positive integers  
step_size 0.01 Positive numbers  
loss_function "Trivial Loss" "Trivial Loss","Huber Loss","Soft L One Loss","Cauchy Loss","Arctan Loss","Tolerant Loss"  
loss_func_param_one 0.5 Number Required for all loss_function values except “Trivial Loss”
loss_func_param_two 0.5 Number Required when loss_function is “Tolerant Loss”
x_ray_residuals_type "Normal Residuals" "Normal Residuals","Ratio Residuals","Log Residuals"  
minimizer_type "Trust Region" "Line Search","Trust Region"  
trust_region_strategy_type "Dogleg" "Levenberg-Marquardt","Dogleg" minimizer_type is "Trust Region"
dogleg_type "Traditional Dogleg" "Traditional Dogleg","Subspace Dogleg" trust_region_strategy_type is "Dogleg"
line_search_type "Armijo" "Armijo","Wolfe" minimizer_type is "Line Search"
line_search_direction_type "Steepest Descent" "Steepest Descent","Nonlinear Conjugate Gradient","L-BFGS","BFGS" minimizer_type is "Line Search". if line_search_type is "Armijo", cannot be "BFGS" or "L-BFGS".
nonlinear_conjugate_gradient_type "" "Fletcher Reeves","Polak Ribirere","Hestenes Stiefel" linear_search_direction_type is "Nonlinear Conjugate Gradient"

Any property can then be easily changed, for example,

fit_pref.convergence= 0.5

If the user tries to set a property to an invalid value they will get an error.

Domain

The Domain class describes the parameter tree.

The root of the tree is the Domain class. This class contains an array of Population classes. Each Population can contain a number of Model classes. Some models have children, which are also models.

Models

Domain and Population are two special kinds of models.

The Domain model is the root of the parameter tree, which can contain multiple populations. Populations can contain standard types of models.

The available standard model classes are:

  • UniformHollowCylinder
  • Sphere
  • SymmetricLayeredSlabs
  • AsymmetricLayeredSlabs
  • Helix
  • DiscreteHelix
  • SpacefillingSymmetry
  • ManualSymmetry
  • PDB- a PDB file
  • AMP- an amplitude grid file

You can create any model by calling its initialization.

Please note that models are dynamically loaded from those available in D+. Therefore, your code editor may underline the model in red even if the model exists.

All models have location_params (Location Parameters) and extra_params (Extra Parameters). Some models (that support layers) also contain layer_params (Layer Parameters). These are all collection of instances of the Parameter class, and can be accessed from model.location_params, model.extra_params, and model.layer_params, respectively.

All of these can be modified. They are accessed using dictionaries. Example:

from dplus.DataModels.models import UniformHollowCylinder

uhc=UniformHollowCylinder()
uhc.layer_params[1]["Radius"].value=2.0
uhc.extra_params["Height"].value=3.0
uhc.location_params["x"].value=2

For additional information about which models have layers and what the various parameters available for each model are, please consult the D+ User’s Manual.

Parameters

The Parameter class contains the following properties:

value: a float whose default value is 0

sigma: a float whose default value is 0

mutable: a boolean whose default value is False

constraints: an instance of the Constraints class, its default value is the default Constraints

Usage:

p=Parameter()  #creates a parameter with value: '0', sigma: '0', mutable: 'False', and the default constraints.
p=Parameter(7) #creates a parameter with value: '7', sigma: '0', mutable: 'False', and the default constraints.
p=Parameter(sigma=2) #creates a parameter with value: '0', sigma: '2', mutable: 'False', and the default constraints.
p.value= 4  #modifies the value to be 4.
p.mutable=True #modifies the value of mutable to be 'True'.
p.sigma=3 #modifies sigma to be 3.
p.constraints=Constraints(min_val=5) #sets constraints to a 'Constraints' instance whose minimum value (min_val) is 5.

Constraints

The Constraints class contains the following properties:

MaxValue: a float whose default value is infinity.

MinValue: a float whose default value is -infinity.

The usage is similar to ‘Parameter’ class, for example:

c=Constraints(min_val=5) #creates a 'Constraints' instance whose minimum value is 5 and whose maximum value is the default ('infinity').

CalculationInput

The CalculationInput class inherits from the State class and therefore has access to all its functions and properties.

In addition, it contains the following properties of its own:

  • x: an array of q values
  • y: an array of intensity values from a signal, optional. Used for running fitting.
  • use_gpu: a boolean whose default value is True, representing whether D+ should use the GPU
  • args: a json dictionary of the arguments required to run generate.exe or fit.exe

the function load_graph can load x and y values from an ordered or unordered dictionary of x:y pairs the function load_signal_file can load x and y values from an existing signal file

A new instance of CalculationInput can be created simply by calling its constructor.

An empty constructor will cause CalculationInput to be created with default values derived from the default State.

Alternately, the constructor can be called with either graph or x and/or y provided as arguments, and these will then be used to overrie the default values derived from the default state.

In addition, CalculationInput has the following static methods to create an instance of GenerateInput:

  • load_from_state_file receives the location of a file that contains a serialized parameter tree (state)
  • load_from_PDB receives the location of a PDB file, and automatically creates a guess at the best state parameters based on the PDB
  • copy_from_state returns a new CalculationInput based on an existing state or CalculationInput
from dplus.CalculationInput import CalculationInput
gen_input=CalculationInput()

from dplus.CalculationInput import CalculationInput
gen_input=CalculationInput.load_from_state_file('sphere.state')

from dplus.CalculationInput import CalculationInput
signal = SignalFileReader("signal_file.out")
fit_input = CalculationInput(x=signal.x_vec, y=signal.y_vec)

Amplitudes

In the module Amplitudes there is the class Grid and the class Amplitude which inherits from Grid.

Please note: The class Amplitude is a purely Python class, not to be confused with the class AMP from Dplus.DataModels.Models

The class AMP contains a filename pointing to an amplitude file, an extra parameter scale, a boolean centered, and it can be serialized and sent as part of the Domain parameter tree to D+.

The class Amplitude, by contrast, can be used to build an amplitude and then save that amplitude as an amplitude file, which can then be opened in D+ (or sent in a class AMP) but it itself cannot be added directly to the Domain parameter tree. If you want to add it, you must save the amplitude to a file first using the save method, and then you can use the State’s function add_amplitude, to add it to the tree.

The class Grid is initialized with q_max and grid_size.

Grid is used to create/describe a grid of q, theta, phi angle values.

These values can be described using two sets of indexing:

  1. The overall index m
  2. The individual angle indices i, j, k

The Grid is created in spherical coordinates in reciprocal space. It has N shells, and the parametergrid_size is equal to 2N. The index i represents the shell number that is related to q , which is the magnitude of the scattering vector. q_max is the largest q value. The index j corresponds to the polar (theta) angle on the ith shell, and the index k corresponds to the azimuthal angle, phi , of the jth polar angle on the ith shell. The Grid is nonuniform and the ith shell contains 6i(3i+1) points in its theta-phi plane. The index m is a single index that describe each point on the Grid . The index starts at the origin of the Grid, where m=0 , and continues to the next shells, whereas each shell is arranged in a phi-major storage order. There is a one-to-one relation between the two indexing methods.

Gridhas the following methods:

  • create_grid: a generator that returns q, theta, phi angles in phi-major order
  • indices_from_index: receives an overall index m, and returns the individual q, theta, and phi indices: i, j, k
  • angles_from_index: receives an overall index m, and returns the matching q, theta, and phi angle values
  • angles_from_indices: receives angle indices i,j,k and returns their q, theta, and phi angle values
  • index_from_indices: receives angle indices i,j,k and returns the overall index m that matches them
  • indices_from_angles: receives angles q, theta, phi, ands returns the matching indices i,j,k
  • index_from_angles: receives angles q, theta, phi and returns the matching overall index m
from dplus.Amplitudes import Grid

g=Grid(5, 100)
for q,theta,phi in g.create_grid():
    print(g.index_from_angles(q, theta, phi))

The class Amplitude inherits from Grid. It is a class intended to describe the amplitude of a model/function, and can save these values to an amplitude file (that can be read by D+) and can also read amplitude files (like those created by D+)

Like a grid, Amplitude is initialized with q_max and grid_size.

Amplitude overrides the create_grid method of Grid. create_grid of Amplitude requires a function as an argument. This function must receive q, theta, and phi, and returns two values, representing the real and imaginary parts of the amplitude’s complex number. The values can be returned as a tuple (a sequence of immutable Python objects), an array, or a Python complex number (A+Bj). These values are then saved to the Ampltiude’s values property, and can also be accessed through the complex_amplitude_array property as a numpy array of numpy complex types.

These values are then saved to the Ampltiude’s values property, and can also be accessed through the complex_amplitudes_array property as a numpy array of numpy complex types.

Alternately, Amplitude has a static method, load, which receives a filename of an Amplitude file, and returns an Amplitude instance with the values from that file already loaded.

Finally, there is the method save, which will save the information in the Amplitude class to an Amplitude file which can then be passed along to D+ to calculate its signal or perform fitting.

It has the following properties:

  • headers: a list that contains data about the class

  • description: an optional string the user can fill with data about the amplitude class (for example what the type of the model). The description property will be added to the headers.

    from dplus.Amplitudes import Amplitude
my_amp=Amplitude.load("myamp.amp")
for c in my_amp.complex_amplitude_array:
    print(c)

from dplus.Amplitudes import Amplitude

def my_func(q, theta, phi):
    return q+1, 0

a=Amplitude(7.5, 200)
a.description= "An exmaple amplitude"
a.create_grid(my_func)
a.save("myfile.amp")

There are examples of using Amplitudes to implement models similar to D+ in the additional examples section.

The module Amplitudes also contains two convenience functions for converting between cartesian and spherical coordinates:

  • sph2cart receives r, theta, phi and returns x, y, z
  • cart2sph receives x, y, z and returns r, theta, phi
from dplus.Amplitudes import sph2cart, cart2sph

q, theta, phi = cart2sph(1,2,3)
x, y, z = sph2cart(q,theta,phi)

CalculationResult

The CalculationResult class is returned by the CalculationRunner. The user should generally not be instantiating the class themselves.

The base CalculationResult class is inherited by GenerateResult and FitResult

CalculationResult has the following properties:

  • graph: an OrderedDict whose keys are x values and whose values are y values.
  • y: The raw list of y values from the results JSON
  • error : returns the JSON error report from the dplus run

In addition, CalculationResults has the following functions:

  • get_amp(model_ptr, destination_folder): returns the file location of the amplitude file for given model_ptr. destination_folder has a default value of None, but if provided, the amplitude file will be copied to that location, and then have its address returned.
  • get_amps(destionation_folder): returns an array of file locations for every amplitude file created during the D+ calculation process. destination_folder has a default value of None, but if provided, the amplitude files will be copied to that location.
  • get_pdb(mod_ptr, destination_folder): returns the file location of the PDB file for given model_ptr. destination_folder has a default value of None, but if provided, the PDB file will be copied to that location, and then have its address returned
  • save_to_out_file(filename): receives file name, and saves the results to the file.

In addition to the above:

GenerateResult has a property headers, created by D+ to describe the job that was run. It is an Ordered Dictionary, whose keys are ModelPtrs and whose values are the header associated.

FitResult has two additional properties, * parameter_tree: A JSON of parameters (can be used to create a new state with state’s load_from_dictionary). Only present in fitting, not generate, results * result_state: a CalculationInput whose Domain contains the optimized parameters obtained from the fitting

FileReaders

The API contains a module FileReaders.

Presently all it contains is SignalFileReader, which can be initialized with a path to a signal file (eg a .out or .dat file) and will read that file into its x_vec, y_vec, and graph properties.

Additional Usage examples

*Example One*

from dplus.CalculationInput import CalculationInput
from dplus.CalculationRunner import LocalRunner

exe_directory = r"C:\Program Files\D+\bin"
sess_directory = r"session"
runner= LocalRunner(exe_directory, sess_directory)

input=CalculationInput.load_from_state_file('spherefit.state')
result=runner.fit(input)
print(result.graph)

Comments: This program loads a state file from spherefit.state, runs fitting with the local runner, and print the graph of the result.

*Example Two*

from dplus.CalculationInput import CalculationInput
from dplus.CalculationRunner import LocalRunner
from dplus.DataModels import ModelFactory, Population
from dplus.State import State
from dplus.DataModels.models import UniformHollowCylinder

sess_directory = r"session"
runner= LocalRunner(session_directory=sess_directory)

uhc=UniformHollowCylinder()
caldata = CalculationInput()
caldata.Domain.populations[0].add_model(uhc)

result=runner.generate(caldata)
print(result.graph)

*Example Three*

from dplus.CalculationRunner import LocalRunner
from dplus.CalculationInput import CalculationInput

runner=LocalRunner()
caldata=CalculationInput.load_from_PDB('1JFF.pdb', 5)
result=runner.generate(caldata)
print(result.graph)

*Example Four*

from dplus.CalculationRunner import LocalRunner
from dplus.CalculationInput import CalculationInput
runner=LocalRunner()
input = CalculationInput.load_from_state_file("uhc.state")
cylinder = input.get_model("test_cylinder")

print("Original radius is ", cylinder.layer_params[1]['Radius'].value)
result = runner.generate(input)

input.load_graph(result.graph)
cylinder = input.get_model("test_cylinder")
cylinder.layer_params[1]['Radius'].value = 2
cylinder.layer_params[1]['Radius'].mutable = True
input.FittingPreferences.convergence = 0.5
input.use_gpu = True
fit_result = runner.fit(input)
optimized_input= fit_result.result_state
result_cylinder=optimized_input.get_model("test_cylinder")
print(fit_result.parameter_tree)
print("Result radius is ", result_cylinder.layer_params[1]['Radius'].value)

Comments: fit_result.result_state is the optimized state (i.e. the optimized parameter tree) that is returned from the fitting (runner.fit(input)). You can fetch the cylinder whose name is “test_cylinder” from that parameter tree, to see what its new optimized parameters are.

For the purpose of these exmaples the models are implemented with minimal default parameters, in a realistic usage scenario the user would set those parameters as editable properties to be changed at his convenience.

from dplus.Amplitudes import Amplitude
import math

class UniformSphere:
    def __init__(self):
        self.extraParams=[1,0]
        self.ED=[333, 400]
        self.r=[0,1]

    @property
    def nLayers(self):
        return len(self.ED)

    def calculate(self, q, theta, phi):
        cos=math.cos
        sin=math.sin
        nLayers=self.nLayers
        ED=self.ED
        extraParams=self.extraParams
        r=self.r
        def closeToZero(x):
            return (math.fabs(x) < 100.0 * 2.2204460492503131E-16)

        if closeToZero(q):
            electrons = 0.0
            for i in range( 1, nLayers):
                electrons += (ED[i] - ED[0]) * (4.0 / 3.0) * math.pi * (r[i] ** 3 - r[i-1] ** 3)
            return (electrons  * extraParams[0] + extraParams[1], 0.0)

        res = 0.0

        for i in range(nLayers-1):
            res -= (ED[i] - ED[i + 1]) * (cos(q * r[i]) * q * r[i] - sin(q * r[i]))
        res -= (ED[nLayers - 1] - ED[0]) * (cos(q * r[nLayers - 1]) * q * r[nLayers - 1] - sin(q * r[nLayers - 1]))

        res *= 4.0 * math.pi / (q*q * q)

        res *= extraParams[0] #Multiply by scale
        res += extraParams[1] #Add background

        return (res, 0.0)

sphere=UniformSphere()
a=Amplitude(7.5, 200)
a.create_grid(sphere.calculate)
a.save("sphere.amp")

input = CalculationInput()
amp_model = input.add_amplitude(a)
amp_model.centered=True
runner=LocalRunner()
result=runner.generate(input)

class SymmetricSlab:
    def __init__(self):
        self.scale=1
        self.background=0
        self.xDomain=10
        self.yDomain=10
        self.ED=[333, 280]
        self.width=[0,1]
        self.OrganizeParameters()

    @property
    def nLayers(self):
        return len(self.ED)

    def OrganizeParameters(self):
        self.width[0] = 0.0
        self.xDomain *= 0.5
        self.yDomain *= 0.5
        for i in range(2, self.nLayers):
            self.width[i] += self.width[i - 1];

    def calculate(self, q, theta, phi):
        def closeToZero(x):
            return (math.fabs(x) < 100.0 * 2.2204460492503131E-16)
        from dplus.Amplitudes import sph2cart
        from math import sin, cos
        from numpy import sinc
        import numpy as np
        qx, qy, qz = sph2cart(q, theta, phi)
        res= np.complex128(0+0j)
        if(closeToZero(qz)):
            for i in range(self.nLayers):
                res += (self.ED[i] - self.ED[0]) * 2. * (self.width[i] - self.width[i - 1])
            return res * 4. * sinc(qx * self.xDomain) * self.xDomain * sinc(qy * self.yDomain) * self.yDomain

        prevSin = np.float64(0.0)
        currSin=np.float64(0.0)
        for i in range(1, self.nLayers):
            currSin = sin(self.width[i] * qz)
            res += (self.ED[i] - self.ED[0]) * 2. * (currSin - prevSin) / qz
            prevSin = currSin
        res *= 4. * sinc((qx * self.xDomain)/np.pi) * self.xDomain * sinc((qy * self.yDomain)/np.pi) * self.yDomain
        return res * self.scale + self.background #Multiply by scale and add background



from dplus.Amplitudes import Amplitude
from dplus.State import State
from dplus.CalculationRunner import LocalRunner
from dplus.CalculationInput import CalculationInput
sphere = SymmetricSlab()
a = Amplitude(7.5, 80)
a.create_grid(sphere.calculate)

It is possible to fit a curve using the results from Generate and numpy’s built in minimization/curve fitting functions. All that is requires is wrapping the interface code so that it receives and returns parameters the way scipy expects (eg as numpy arrays)

An example follows:

import numpy as np
from scipy import optimize
from dplus.CalculationInput import CalculationInput
from dplus.CalculationRunner import LocalRunner

input=CalculationInput.load_from_state_file(r"2_pops.state")
generate_runner=LocalRunner()

def run_generate(xdata, *params):
    '''
    scipy's optimization algorithms require a function that receives an x array and an array of parameters, and
    returns a y array.
    this function will be called repeatedly, until scipy's optimization has completed.
    '''
    input.set_mutable_parameter_values(params) #we take the parameters given by scipy and place them inside our parameter tree
    generate_results=generate_runner.generate(input) #call generate
    return np.array(generate_results.y) #return the results of the generate call

x_data=input.x
y_data=input.y
p0 = input.get_mutable_parameter_values()
method='lm' #lenenberg-marquadt (see scipy documentation)
popt, pcov =optimize.curve_fit(run_generate, x_data, y_data, p0=p0, method=method)

#popt is the optimized set of parameters from those we have indicated as mutable
#we can insert them back into our CalculationInput and create the optmized parameter tree
input.set_mutable_parameter_values(popt)
#we can run generate to get the results of generate with them
best_results=generate_runner.generate(input)