How to adjust the time step in devito?

[acse-yw11823]

Hello, I am currently comparing Devito with Spyro. To ensure an accurate comparison of the shot records, I need both to share the same timestep dt. I am working on the simplest example to achieve this. Does anyone know how to manually adjust the timestep in Devito? Here is my code:

# Define true and initial model
shape = (101, 101)  # Number of grid point (nx, nz)
spacing = (10., 10.)  # Grid spacing in m. The domain size is now 1km by 1km
origin = (0., 0.)  # Need origin to define relative source and receiver locations

#Set the number of boundary layers
nbl = 40

#True Vp model
model = demo_model('circle-isotropic', vp_circle=3.0, vp_background=2.5,
                    origin=origin, shape=shape, spacing=spacing, nbl=nbl)

#Smooth/Initial Vp model
model0 = demo_model('circle-isotropic', vp_circle=2.5, vp_background=2.5,  
                     origin=origin, shape=shape, spacing=spacing, nbl=nbl,
                    grid = model.grid)

# Define acquisition geometry: 
# nshots = 9  # Number of shots to used to generate the gradient
nreceivers = 101  # Number of receiver locations per shot 
# fwi_iterations = 5  # Number of outer FWI iterations

# Note, distances below correspond to meters.
# Position the source:
src_coordinates = np.empty((1, 2))
src_coordinates[0, 1] = np.array(model.domain_size[1]) * .5
src_coordinates[0, 0] = 20.

# Initialize receivers for synthetic and imaging data
rec_coordinates = np.empty((nreceivers, 2))
rec_coordinates[:, 1] = np.linspace(0, model.domain_size[0], num=nreceivers)
rec_coordinates[:, 0] = 980.

# Create the Geometry
# Along with storing the source and receiver locations defined above this will work out the points in time at
# at which we'll need the source signal and compute them according to the definiction of the Ricker-wavelet
t0 = 0.
tn = 1000. # 1000ms
f0 = 0.010 # 10Hz (=0.01 kHz)
geometry = AcquisitionGeometry(model, rec_coordinates, src_coordinates, t0, tn, f0=f0, src_type='Ricker')

solver = AcousticWaveSolver(model, geometry, space_order=4)

# Compute synthetic data with forward operator and calculate the total running time
t1=time.time()
true_d,a, b = solver.forward(vp=model.vp)
end_time = time.time()
running_time = end_time - t1
# Print the running time
print("Running Time - devito: {:.2f} seconds".format(running_time))

# Compute initial data with forward operator 
smooth_d, _, _ = solver.forward(vp=model0.vp)

Many thanks for the help!!!!

[mloubout]

You can give dt to the model Model(..., dt=my_dt) just make sure it's a stable value.

You can also interpolate the output with rec.resample(dt=new_dt)

[acse-yw11823]

Many thanks!!!