# gauss_seidel_x#

emg3d.core.gauss_seidel_x(ex, ey, ez, sx, sy, sz, eta_x, eta_y, eta_z, zeta, hx, hy, hz, nu)[source]#

Gauss-Seidel method with line relaxation in x-direction.

This is the equivalent to gauss_seidel, but with line relaxation in the x-direction. See gauss_seidel for more details on the smoother itself.

The resulting system A x = b to solve consists of n unknowns (x-vector), and the corresponding matrix A is a banded matrix with the main diagonal and five upper and lower diagonals:

.-0
|X|\   0
0-.-0       left:  middle:  right:
\|X|\                      (not used)
0-.-0      0-     .-      0
\|X|\      \     |X      |\
0-.-0
0   \|X|
0-.

. 1*1, - 4*1, | 1*4, X 4*4, \ 4*4 upper or lower

The matrix A is complex and symmetric (A = A^T), and therefore only the main diagonal and the lower five off-diagonals are required.

• The right-hand-side b has length 5*nx-4 (nx even).

• The matrix A has length of b and 1+2*5 diagonals; we use for it an array of length 6*len(b).

The values are computed in rows of 5 lines, with the indicated middle and left matrices as indicated in the above scheme. These blocks are filled into the main matrix A and vector b, and subsequently solved with a non-standard Cholesky factorisation implemented in solve. Tangential components at the boundaries are assumed to be zero (PEC boundaries).

The result is stored in the provided electric field components ex, ey, and ez.

Parameters:
ex, ey, ezndarray

Electric fields in x-, y-, and z-directions (emg3d.fields.Field).

sx, sy, szndarray

Source fields in x-, y-, and z-directions (emg3d.fields.Field).

eta_x, eta_y, eta_z, zetandarray

Volume-averaged model parameters (emg3d.models.VolumeModel).

hx, hy, hzndarray

Cell widths in x-, y-, and z-directions (emg3d.meshes.TensorMesh).

nuint

Number of Gauss-Seidel iterations.