# Basic Forward 2D DC Resistivity#

2D DC forward modeling example with Tensor and Curvilinear Meshes

```import discretize
from pymatsolver import SolverLU
import numpy as np
import matplotlib.pyplot as plt

def run(plotIt=True):
# Step1: Generate Tensor and Curvilinear Mesh
sz = [40, 40]
tM = discretize.TensorMesh(sz)
rM = discretize.CurvilinearMesh(discretize.utils.exampleLrmGrid(sz, "rotate"))

# Step2: Direct Current (DC) operator
def DCfun(mesh, pts):
D = mesh.faceDiv
sigma = 1e-2 * np.ones(mesh.nC)
MsigI = mesh.getFaceInnerProduct(sigma, invProp=True, invMat=True)
A = -D * MsigI * D.T
A[-1, -1] /= mesh.vol[-1]  # Remove null space
rhs = np.zeros(mesh.nC)
txind = discretize.utils.closestPoints(mesh, pts)
rhs[txind] = np.r_[1, -1]
return A, rhs

pts = np.vstack((np.r_[0.25, 0.5], np.r_[0.75, 0.5]))

# Step3: Solve DC problem (LU solver)
AtM, rhstM = DCfun(tM, pts)
AinvtM = SolverLU(AtM)
phitM = AinvtM * rhstM

ArM, rhsrM = DCfun(rM, pts)
AinvrM = SolverLU(ArM)
phirM = AinvrM * rhsrM

if not plotIt:
return

# Step4: Making Figure
fig, axes = plt.subplots(1, 2, figsize=(12 * 1.2, 4 * 1.2))
vmin, vmax = phitM.min(), phitM.max()

dat = tM.plotImage(phitM, ax=axes[0], clim=(vmin, vmax), grid=True)
cb0 = plt.colorbar(dat[0], ax=axes[0])
cb0.set_label("Voltage (V)")
axes[0].set_title("TensorMesh")

dat = rM.plotImage(phirM, ax=axes[1], clim=(vmin, vmax), grid=True)
cb1 = plt.colorbar(dat[0], ax=axes[1])
cb1.set_label("Voltage (V)")
axes[1].set_title("CurvilinearMesh")

if __name__ == "__main__":
run()
plt.show()
```

Total running time of the script: ( 0 minutes 0.367 seconds)

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