Adding fixamp ics

README.md

@@ -4,7 +4,7 @@
 <!-- ALL-CONTRIBUTORS-BADGE:END -->
 JAX-powered Cosmological Particle-Mesh N-body Solver
 
-**This project is currently in an early design phased. All inputs are welcome on the [design document](https://github.com/DifferentiableUniverseInitiative/JaxPM/blob/main/design.md)**
+**This project is currently in an early design phase. All inputs are welcome on the [design document](https://github.com/DifferentiableUniverseInitiative/JaxPM/blob/main/design.md)**
 
 ## Goals
 

dev/test_script.py

@@ -0,0 +1,63 @@
+# Start this script with:
+# mpirun -np 4 python test_script.py
+import os
+os.environ["XLA_FLAGS"] = '--xla_force_host_platform_device_count=4'
+import matplotlib.pylab as plt
+import jax 
+import numpy as np
+import jax.numpy as jnp
+import jax.lax as lax
+from jax.experimental.maps import mesh, xmap
+from jax.experimental.pjit import PartitionSpec, pjit
+import tensorflow_probability as tfp; tfp = tfp.substrates.jax
+tfd = tfp.distributions
+
+def cic_paint(mesh, positions):
+  """ Paints positions onto mesh
+  mesh: [nx, ny, nz]
+  positions: [npart, 3]
+  """
+  positions = jnp.expand_dims(positions, 1)
+  floor = jnp.floor(positions)
+  connection = jnp.array([[[0, 0, 0], [1., 0, 0], [0., 1, 0], 
+                           [0., 0, 1], [1., 1, 0], [1., 0, 1], 
+                           [0., 1, 1], [1., 1, 1]]])
+
+  neighboor_coords = floor + connection
+  kernel = 1. - jnp.abs(positions - neighboor_coords)
+  kernel = kernel[..., 0] * kernel[..., 1] * kernel[..., 2]  
+
+  dnums = jax.lax.ScatterDimensionNumbers(
+    update_window_dims=(),
+    inserted_window_dims=(0, 1, 2),
+    scatter_dims_to_operand_dims=(0, 1, 2))
+  mesh = lax.scatter_add(mesh, 
+                         neighboor_coords.reshape([-1,8,3]).astype('int32'), 
+                         kernel.reshape([-1,8]),
+                         dnums)
+  return mesh
+
+# And let's draw some points from some 3D distribution
+dist = tfd.MultivariateNormalDiag(loc=[16.,16.,16.], scale_identity_multiplier=3.)
+pos = dist.sample(1e4, seed=jax.random.PRNGKey(0))
+
+f = pjit(lambda x: cic_paint(x, pos),
+         in_axis_resources=PartitionSpec('x', 'y', 'z'), 
+         out_axis_resources=None)
+
+devices = np.array(jax.devices()).reshape((2, 2, 1))
+
+# Let's import the mesh
+m = jnp.zeros([32, 32, 32])
+
+with mesh(devices, ('x', 'y', 'z')):
+  # Shard the mesh, I'm not sure this is absolutely necessary
+  m = pjit(lambda x: x,
+           in_axis_resources=None,
+           out_axis_resources=PartitionSpec('x', 'y', 'z'))(m)
+
+  # Apply the sharded CiC function
+  res = f(m)
+
+plt.imshow(res.sum(axis=2))
+plt.show()