Add CI test for velocity coincidence thinning (#4919)

* add CI test for Cartesian velocity grid in resampling

* avoid unneeded picmi input parameters

* set checksum values for new test

* use seperate input file for new example

Examples/Tests/resampling/inputs_1d_velocity_coincidence_thinning_cartesian

@@ -0,0 +1,45 @@
+max_step = 4
+warpx.verbose = 1
+warpx.const_dt = 1e-10
+amr.n_cell = 256
+amr.max_grid_size = 64
+amr.max_level = 0
+geometry.dims = 1
+geometry.prob_lo = 0
+geometry.prob_hi = 0.1
+
+# Boundary condition and field solver
+boundary.field_lo = periodic
+boundary.field_hi = periodic
+boundary.particle_lo = periodic
+boundary.particle_hi = periodic
+algo.particle_shape = 1
+algo.maxwell_solver = none
+
+particles.species_names = hydrogen
+hydrogen.mass = 1.67262192369e-27
+hydrogen.charge = 1.602176634e-19
+hydrogen.injection_style = nrandompercell
+hydrogen.initialize_self_fields = 0
+hydrogen.do_not_push = 1
+hydrogen.do_resampling = 1
+hydrogen.resampling_min_ppc = 10
+hydrogen.resampling_trigger_intervals = 1::2
+hydrogen.resampling_algorithm = velocity_coincidence_thinning
+hydrogen.resampling_algorithm_velocity_grid_type = cartesian
+hydrogen.resampling_algorithm_delta_u = 10000000.0 5000000.0 7000000.0
+hydrogen.num_particles_per_cell = 2500
+hydrogen.momentum_distribution_type = gaussian
+hydrogen.ux_m = 0.0
+hydrogen.uy_m = 0.0
+hydrogen.uz_m = 0.0
+hydrogen.ux_th = 0.000326
+hydrogen.uy_th = 0.000326
+hydrogen.uz_th = 0.000326
+hydrogen.profile = constant
+hydrogen.density = 1e+19
+
+# Diagnostics
+diagnostics.diags_names = diag1
+diag1.intervals = 4
+diag1.diag_type = Full

Python/pywarpx/picmi.py

@@ -254,7 +254,7 @@ def init(self, kw):
         self.resampling_algorithm_n_theta = kw.pop('warpx_resampling_algorithm_n_theta', None)
         self.resampling_algorithm_n_phi = kw.pop('warpx_resampling_algorithm_n_phi', None)
         self.resampling_algorithm_delta_u = kw.pop('warpx_resampling_algorithm_delta_u', None)
-        if np.size(self.resampling_algorithm_delta_u) == 1:
+        if self.resampling_algorithm_delta_u is not None and np.size(self.resampling_algorithm_delta_u) == 1:
             self.resampling_algorithm_delta_u = [self.resampling_algorithm_delta_u]*3
 
     def species_initialize_inputs(self, layout,

Regression/Checksum/benchmarks_json/resample_velocity_coincidence_thinning_cartesian.json

@@ -0,0 +1,20 @@
+{
+  "lev=0": {
+    "Bx": 0.0,
+    "By": 0.0,
+    "Bz": 0.0,
+    "Ex": 0.0,
+    "Ey": 0.0,
+    "Ez": 0.0,
+    "jx": 434240.88525516074,
+    "jy": 315768.9402331213,
+    "jz": 642846.5589763735
+  },
+  "hydrogen": {
+    "particle_momentum_x": 6.919253235905925e-20,
+    "particle_momentum_y": 7.069867215063566e-20,
+    "particle_momentum_z": 7.606884436016626e-20,
+    "particle_position_x": 25.60006676227001,
+    "particle_weight": 1.0000000000000001e+18
+  }
+}

Regression/WarpX-tests.ini

@@ -4206,6 +4206,23 @@ doVis = 0
 compareParticles = 0
 analysisRoutine = Examples/analysis_default_regression.py
 
+[resample_velocity_coincidence_thinning_cartesian]
+buildDir = .
+inputFile = Examples/Tests/resampling/inputs_1d_velocity_coincidence_thinning_cartesian
+runtime_params =
+dim = 1
+addToCompileString =
+cmakeSetupOpts = -DWarpX_DIMS=1
+restartTest = 0
+useMPI = 1
+numprocs = 2
+useOMP = 1
+numthreads = 1
+compileTest = 0
+doVis = 0
+compareParticles = 0
+analysisRoutine = Examples/analysis_default_regression.py
+
 [restart]
 buildDir = .
 inputFile = Examples/Tests/restart/inputs