.. DO NOT EDIT. .. THIS FILE WAS AUTOMATICALLY GENERATED BY SPHINX-GALLERY. .. TO MAKE CHANGES, EDIT THE SOURCE PYTHON FILE: .. "content/tutorials/02-linear_inversion/plot_inv_1_inversion_lsq.py" .. LINE NUMBERS ARE GIVEN BELOW. .. only:: html .. note:: :class: sphx-glr-download-link-note :ref:`Go to the end ` to download the full example code .. rst-class:: sphx-glr-example-title .. _sphx_glr_content_tutorials_02-linear_inversion_plot_inv_1_inversion_lsq.py: Linear Least-Squares Inversion ============================== Here we demonstrate the basics of inverting data with SimPEG by considering a linear inverse problem. We formulate the inverse problem as a least-squares optimization problem. For this tutorial, we focus on the following: - Defining the forward problem - Defining the inverse problem (data misfit, regularization, optimization) - Specifying directives for the inversion - Recovering a set of model parameters which explains the observations .. GENERATED FROM PYTHON SOURCE LINES 18-21 Import Modules -------------- .. GENERATED FROM PYTHON SOURCE LINES 21-41 .. code-block:: default import numpy as np import matplotlib.pyplot as plt from discretize import TensorMesh from SimPEG import ( simulation, maps, data_misfit, directives, optimization, regularization, inverse_problem, inversion, ) # sphinx_gallery_thumbnail_number = 3 .. GENERATED FROM PYTHON SOURCE LINES 42-48 Defining the Model and Mapping ------------------------------ Here we generate a synthetic model and a mappig which goes from the model space to the row space of our linear operator. .. GENERATED FROM PYTHON SOURCE LINES 48-69 .. code-block:: default nParam = 100 # Number of model paramters # A 1D mesh is used to define the row-space of the linear operator. mesh = TensorMesh([nParam]) # Creating the true model true_model = np.zeros(mesh.nC) true_model[mesh.cell_centers_x > 0.3] = 1.0 true_model[mesh.cell_centers_x > 0.45] = -0.5 true_model[mesh.cell_centers_x > 0.6] = 0 # Mapping from the model space to the row space of the linear operator model_map = maps.IdentityMap(mesh) # Plotting the true model fig = plt.figure(figsize=(8, 5)) ax = fig.add_subplot(111) ax.plot(mesh.cell_centers_x, true_model, "b-") ax.set_ylim([-2, 2]) .. image-sg:: /content/tutorials/02-linear_inversion/images/sphx_glr_plot_inv_1_inversion_lsq_001.png :alt: plot inv 1 inversion lsq :srcset: /content/tutorials/02-linear_inversion/images/sphx_glr_plot_inv_1_inversion_lsq_001.png :class: sphx-glr-single-img .. rst-class:: sphx-glr-script-out .. code-block:: none (-2.0, 2.0) .. GENERATED FROM PYTHON SOURCE LINES 70-77 Defining the Linear Operator ---------------------------- Here we define the linear operator with dimensions (nData, nParam). In practive, you may have a problem-specific linear operator which you would like to construct or load here. .. GENERATED FROM PYTHON SOURCE LINES 77-108 .. code-block:: default # Number of data observations (rows) nData = 20 # Create the linear operator for the tutorial. The columns of the linear operator # represents a set of decaying and oscillating functions. jk = np.linspace(1.0, 60.0, nData) p = -0.25 q = 0.25 def g(k): return np.exp(p * jk[k] * mesh.cell_centers_x) * np.cos( np.pi * q * jk[k] * mesh.cell_centers_x ) G = np.empty((nData, nParam)) for i in range(nData): G[i, :] = g(i) # Plot the columns of G fig = plt.figure(figsize=(8, 5)) ax = fig.add_subplot(111) for i in range(G.shape[0]): ax.plot(G[i, :]) ax.set_title("Columns of matrix G") .. image-sg:: /content/tutorials/02-linear_inversion/images/sphx_glr_plot_inv_1_inversion_lsq_002.png :alt: Columns of matrix G :srcset: /content/tutorials/02-linear_inversion/images/sphx_glr_plot_inv_1_inversion_lsq_002.png :class: sphx-glr-single-img .. rst-class:: sphx-glr-script-out .. code-block:: none Text(0.5, 1.0, 'Columns of matrix G') .. GENERATED FROM PYTHON SOURCE LINES 109-115 Defining the Simulation ----------------------- The simulation defines the relationship between the model parameters and predicted data. .. GENERATED FROM PYTHON SOURCE LINES 115-118 .. code-block:: default sim = simulation.LinearSimulation(mesh, G=G, model_map=model_map) .. GENERATED FROM PYTHON SOURCE LINES 119-125 Predict Synthetic Data ---------------------- Here, we use the true model to create synthetic data which we will subsequently invert. .. GENERATED FROM PYTHON SOURCE LINES 125-133 .. code-block:: default # Standard deviation of Gaussian noise being added std = 0.01 np.random.seed(1) # Create a SimPEG data object data_obj = sim.make_synthetic_data(true_model, relative_error=std, add_noise=True) .. GENERATED FROM PYTHON SOURCE LINES 134-143 Define the Inverse Problem -------------------------- The inverse problem is defined by 3 things: 1) Data Misfit: a measure of how well our recovered model explains the field data 2) Regularization: constraints placed on the recovered model and a priori information 3) Optimization: the numerical approach used to solve the inverse problem .. GENERATED FROM PYTHON SOURCE LINES 143-159 .. code-block:: default # Define the data misfit. Here the data misfit is the L2 norm of the weighted # residual between the observed data and the data predicted for a given model. # Within the data misfit, the residual between predicted and observed data are # normalized by the data's standard deviation. dmis = data_misfit.L2DataMisfit(simulation=sim, data=data_obj) # Define the regularization (model objective function). reg = regularization.WeightedLeastSquares(mesh, alpha_s=1.0, alpha_x=1.0) # Define how the optimization problem is solved. opt = optimization.InexactGaussNewton(maxIter=50) # Here we define the inverse problem that is to be solved inv_prob = inverse_problem.BaseInvProblem(dmis, reg, opt) .. GENERATED FROM PYTHON SOURCE LINES 160-167 Define Inversion Directives --------------------------- Here we define any directiveas that are carried out during the inversion. This includes the cooling schedule for the trade-off parameter (beta), stopping criteria for the inversion and saving inversion results at each iteration. .. GENERATED FROM PYTHON SOURCE LINES 167-179 .. code-block:: default # Defining a starting value for the trade-off parameter (beta) between the data # misfit and the regularization. starting_beta = directives.BetaEstimate_ByEig(beta0_ratio=1e-4) # Setting a stopping criteria for the inversion. target_misfit = directives.TargetMisfit() # The directives are defined as a list. directives_list = [starting_beta, target_misfit] .. GENERATED FROM PYTHON SOURCE LINES 180-186 Setting a Starting Model and Running the Inversion -------------------------------------------------- To define the inversion object, we need to define the inversion problem and the set of directives. We can then run the inversion. .. GENERATED FROM PYTHON SOURCE LINES 186-196 .. code-block:: default # Here we combine the inverse problem and the set of directives inv = inversion.BaseInversion(inv_prob, directives_list) # Starting model starting_model = np.zeros(nParam) # Run inversion recovered_model = inv.run(starting_model) .. rst-class:: sphx-glr-script-out .. code-block:: none SimPEG.InvProblem will set Regularization.reference_model to m0. SimPEG.InvProblem will set Regularization.reference_model to m0. SimPEG.InvProblem will set Regularization.reference_model to m0. SimPEG.InvProblem is setting bfgsH0 to the inverse of the eval2Deriv. ***Done using the default solver Pardiso and no solver_opts.*** model has any nan: 0 ============================ Inexact Gauss Newton ============================ # beta phi_d phi_m f |proj(x-g)-x| LS Comment ----------------------------------------------------------------------------- x0 has any nan: 0 0 1.86e+02 1.00e+05 0.00e+00 1.00e+05 1.26e+06 0 1 1.86e+02 4.68e+04 3.50e-01 4.68e+04 8.00e+04 0 2 1.86e+02 3.18e+04 1.35e+00 3.21e+04 5.90e+04 0 3 1.86e+02 1.75e+04 5.21e+00 1.85e+04 5.36e+04 0 Skip BFGS 4 1.86e+02 1.16e+04 5.18e+00 1.25e+04 8.12e+04 0 5 1.86e+02 8.05e+03 8.09e+00 9.55e+03 4.44e+04 0 6 1.86e+02 4.39e+03 1.19e+01 6.59e+03 5.39e+04 0 7 1.86e+02 3.33e+03 1.24e+01 5.65e+03 2.83e+04 0 8 1.86e+02 2.87e+03 1.31e+01 5.30e+03 8.05e+04 0 9 1.86e+02 2.38e+03 1.38e+01 4.95e+03 3.99e+04 0 10 1.86e+02 1.60e+03 1.55e+01 4.48e+03 6.49e+04 0 11 1.86e+02 1.32e+03 1.64e+01 4.37e+03 6.35e+04 0 12 1.86e+02 1.19e+03 1.66e+01 4.28e+03 4.79e+04 0 13 1.86e+02 1.16e+03 1.64e+01 4.21e+03 6.73e+04 0 14 1.86e+02 8.13e+02 1.70e+01 3.97e+03 1.18e+04 0 Skip BFGS 15 1.86e+02 7.05e+02 1.73e+01 3.93e+03 3.04e+04 0 16 1.86e+02 6.36e+02 1.72e+01 3.83e+03 1.64e+04 0 Skip BFGS 17 1.86e+02 6.47e+02 1.70e+01 3.81e+03 1.52e+04 0 18 1.86e+02 6.68e+02 1.68e+01 3.80e+03 2.37e+04 0 Skip BFGS 19 1.86e+02 6.76e+02 1.68e+01 3.80e+03 1.50e+04 0 20 1.86e+02 6.87e+02 1.66e+01 3.77e+03 2.58e+04 0 Skip BFGS 21 1.86e+02 7.06e+02 1.65e+01 3.77e+03 1.47e+04 0 22 1.86e+02 6.48e+02 1.67e+01 3.76e+03 1.26e+04 0 23 1.86e+02 6.29e+02 1.68e+01 3.76e+03 2.26e+04 0 Skip BFGS 24 1.86e+02 6.23e+02 1.68e+01 3.75e+03 1.54e+04 0 25 1.86e+02 5.40e+02 1.72e+01 3.74e+03 1.56e+04 0 Skip BFGS 26 1.86e+02 5.42e+02 1.72e+01 3.74e+03 1.24e+04 0 27 1.86e+02 5.39e+02 1.72e+01 3.74e+03 1.27e+04 0 28 1.86e+02 5.35e+02 1.72e+01 3.73e+03 4.14e+04 0 29 1.86e+02 5.47e+02 1.70e+01 3.72e+03 8.24e+03 0 Skip BFGS 30 1.86e+02 5.45e+02 1.70e+01 3.72e+03 9.25e+03 0 31 1.86e+02 5.32e+02 1.71e+01 3.71e+03 1.01e+04 0 Skip BFGS 32 1.86e+02 5.33e+02 1.71e+01 3.71e+03 1.11e+04 0 33 1.86e+02 5.19e+02 1.72e+01 3.71e+03 1.19e+03 0 Skip BFGS 34 1.86e+02 5.18e+02 1.72e+01 3.71e+03 2.16e+03 0 35 1.86e+02 5.14e+02 1.72e+01 3.71e+03 9.41e+02 0 36 1.86e+02 5.16e+02 1.72e+01 3.71e+03 4.08e+03 0 37 1.86e+02 5.17e+02 1.72e+01 3.71e+03 4.36e+03 0 Skip BFGS 38 1.86e+02 5.17e+02 1.72e+01 3.71e+03 1.69e+03 0 39 1.86e+02 5.17e+02 1.72e+01 3.71e+03 3.17e+03 0 Skip BFGS 40 1.86e+02 5.17e+02 1.72e+01 3.71e+03 2.34e+03 0 41 1.86e+02 5.14e+02 1.72e+01 3.71e+03 1.66e+03 0 Skip BFGS 42 1.86e+02 5.14e+02 1.72e+01 3.71e+03 1.29e+03 0 43 1.86e+02 5.13e+02 1.72e+01 3.71e+03 1.44e+03 0 Skip BFGS 44 1.86e+02 5.13e+02 1.72e+01 3.71e+03 1.56e+03 0 45 1.86e+02 5.13e+02 1.72e+01 3.71e+03 1.63e+03 0 Skip BFGS 46 1.86e+02 5.13e+02 1.72e+01 3.71e+03 1.64e+03 0 47 1.86e+02 5.13e+02 1.72e+01 3.71e+03 1.64e+03 0 48 1.86e+02 5.13e+02 1.72e+01 3.71e+03 2.15e+03 0 Skip BFGS 49 1.86e+02 5.13e+02 1.72e+01 3.71e+03 1.80e+03 0 50 1.86e+02 5.12e+02 1.72e+01 3.71e+03 1.96e+03 0 ------------------------- STOP! ------------------------- 1 : |fc-fOld| = 1.7328e-02 <= tolF*(1+|f0|) = 1.0000e+04 1 : |xc-x_last| = 5.8099e-03 <= tolX*(1+|x0|) = 1.0000e-01 0 : |proj(x-g)-x| = 1.9612e+03 <= tolG = 1.0000e-01 0 : |proj(x-g)-x| = 1.9612e+03 <= 1e3*eps = 1.0000e-02 1 : maxIter = 50 <= iter = 50 ------------------------- DONE! ------------------------- .. GENERATED FROM PYTHON SOURCE LINES 197-200 Plotting Results ---------------- .. GENERATED FROM PYTHON SOURCE LINES 200-212 .. code-block:: default # Observed versus predicted data fig, ax = plt.subplots(1, 2, figsize=(12 * 1.2, 4 * 1.2)) ax[0].plot(data_obj.dobs, "b-") ax[0].plot(inv_prob.dpred, "r-") ax[0].legend(("Observed Data", "Predicted Data")) # True versus recovered model ax[1].plot(mesh.cell_centers_x, true_model, "b-") ax[1].plot(mesh.cell_centers_x, recovered_model, "r-") ax[1].legend(("True Model", "Recovered Model")) ax[1].set_ylim([-2, 2]) .. image-sg:: /content/tutorials/02-linear_inversion/images/sphx_glr_plot_inv_1_inversion_lsq_003.png :alt: plot inv 1 inversion lsq :srcset: /content/tutorials/02-linear_inversion/images/sphx_glr_plot_inv_1_inversion_lsq_003.png :class: sphx-glr-single-img .. rst-class:: sphx-glr-script-out .. code-block:: none (-2.0, 2.0) .. rst-class:: sphx-glr-timing **Total running time of the script:** (0 minutes 31.917 seconds) **Estimated memory usage:** 8 MB .. _sphx_glr_download_content_tutorials_02-linear_inversion_plot_inv_1_inversion_lsq.py: .. only:: html .. container:: sphx-glr-footer sphx-glr-footer-example .. container:: sphx-glr-download sphx-glr-download-python :download:`Download Python source code: plot_inv_1_inversion_lsq.py ` .. container:: sphx-glr-download sphx-glr-download-jupyter :download:`Download Jupyter notebook: plot_inv_1_inversion_lsq.ipynb ` .. only:: html .. rst-class:: sphx-glr-signature `Gallery generated by Sphinx-Gallery `_