what is the value of mlflow nested runs? - mlflow

Question

What is the value of nested runs in mlflow? I thought it would be that a child run inherits params of the parent, but I dont see that
with mlflow.start_run(run_name='myrun'):
mlflow.log_param('kl', '0p0')
mlflow.log_param('name', 'ios')
mlflow.log_metric('mu', 1.0)
with mlflow.start_run(run_name='myrun2', nested=True):
mlflow.log_param('name', 'weighted')
mlflow.log_metric('mu', 2.0)
if I collect the run info in python
df = mlflow.search_runs()
then we have
df['params.kl']
giving
0 None
1 0p0
Name: params.kl, dtype: object

Answer 1

From my understanding, the reason for nested runs are to track a collection of model training within a single run. This would have the structure: experiment --> run 1, run 2, run 3, ... --> run 1-1, run 1-2, run 2-1, run 2-2, run 3-1, run 3-2,...
In other words, the parent/outer mlflow.start_run generates a mlflow experiment entry (first-level run); the child/nested mlflow.start_run generates run-entry (second-level run).