Thank you very much for the explanation. I think I understand.
In my model, I try to fix a multi-task learing problem. As the code following:
beta = pm.MvNormal(‘beta’, mu=np.zeros(num_tasks), chol=L, shape=(num_features,num_tasks))
I specified the row size of beta as well, maybe this caused error. But there are 12 tasks and 24 features, it seems that I do not have another choice~