[TEST] Add tests for CG solver with PYTORCH and PYKEOPS backends

Extended CG solver tests to include configurations using both the PYTORCH and PYKEOPS backends. Configured tests with varying `use_gpu` and `dtype` options, introduced a new Greenstone model test, and added 3D plotting support in the test suite.

Author: Leguark

test/test_modules/test_cg/test_cg_solver.py

@@ -20,7 +20,7 @@ def test_solve_with_cg():
         engine_config=gp.data.GemPyEngineConfig(
             backend=gp.data.AvailableBackends.PYTORCH,
             use_gpu=True,
-            dtype='float32'
+            dtype='float64'
         )
     )
 
@@ -60,3 +60,23 @@ def test_save_weights():
     if PLOT:
         gpv = require_gempy_viewer()
         gpv.plot_3d(model, image=True)
+
+
+def test_keops_x_torch():
+    model = gp.generate_example_model(ExampleModel.GREENSTONE, compute_model=False)
+    print(model.structural_frame)
+
+    WeightCache.clear_cache()
+    BackendTensor.PYKEOPS = True
+    sol = gp.compute_model(
+        gempy_model=model,
+        engine_config=gp.data.GemPyEngineConfig(
+            backend=gp.data.AvailableBackends.PYTORCH,
+            use_gpu=False,
+            dtype='float32'
+        )
+    )
+
+    if PLOT:
+        gpv = require_gempy_viewer()
+        gpv.plot_3d(model, image=True)