upgrading init2winit from pmap to jit

PiperOrigin-RevId: 673695362

precondition/distributed_shampoo.py

@@ -2832,10 +2832,7 @@ def _pmap_compute_preconditioners(states, step, statistics,
     Returns:
       New optimizer states after computing the preconditioner.
     """
-    if batch_axis_name:
-      num_devices = lax.psum(1, batch_axis_name)
-    else:
-      num_devices = 1
+    num_devices = jax.device_count()
     num_statistics = len(statistics)
     # Pad statistics and exponents to next multiple of num_devices.
     packed_statistics = [
@@ -3033,7 +3030,7 @@ def _pmap_quantized_compute_preconditioners(states, step, statistics,
     Returns:
       New optimizer states after computing the preconditioner.
     """
-    num_devices = lax.psum(1, batch_axis_name)
+    num_devices = jax.device_count()
     num_statistics = len(statistics)
     quantized_dtype = quantized_dtype_for_second_moment_statistics_buffers()
     # Complexity here is around: shapes needing be statically shaped,