Hetoutput in the Krusel Smith tutorial

[GuiAll]

Hello everyone

I am learning how to build code with the SSJ with the tutorials (very useful, thanks !). I am trying to figure out where the code generates the (aggregate) outputs A and C :

• The HetBlock scripted in cell 7 and characterized by the backward step generates as outputs Va (the value function), a (the policy for assets) and c (the policy for consumption), i.e. multidimensionnal outputs. The script is :

@het(exogenous='Pi', policy='a', backward='Va', backward_init=household_init) def household(Va_p, a_grid, e_grid, r, w, beta, eis): """Single backward iteration step using endogenous gridpoint method for households with CRRA utility.

Parameters
----------
Va_p     : array (nE, nA), expected marginal value of assets next period
a_grid   : array (nA), asset grid
e_grid   : array (nE), producticity grid
r        : scalar, ex-post real interest rate
w        : scalar, wage
beta     : scalar, discount factor
eis      : scalar, elasticity of intertemporal substitution

Returns
----------
Va : array (nE, nA), marginal value of assets today
a  : array (nE, nA), asset policy today
c  : array (nE, nA), consumption policy today
"""
uc_nextgrid = beta * Va_p
c_nextgrid = uc_nextgrid ** (-eis)
coh = (1 + r) * a_grid[np.newaxis, :] + w * e_grid[:, np.newaxis]
a = interpolate.interpolate_y(c_nextgrid + a_grid, coh, a_grid)
misc.setmin(a, a_grid[0])
c = coh - a
Va = (1 + r) * c ** (-1 / eis)
return Va, a, c

• the outputs stated for the households on cell 8, called by print(f'Macro outputs: {household.outputs}') indicate A and C

However, I do not see any hetoutput that generates A and C from a and c. Is it automatically calculated as part of the HetBlock ? In which case I presume that these macro output are automatically named as capital [name of the corresponding micro input] ? Or am I missing something ?

Thank you in advance !

[bbardoczy]

You're right.

• Both the core backward iteration function (household in your example) and any hetoutput functions that may be attached to it return micro outputs on the grid. Let's call these policies.
• The convention is that policies are lower case. You get an error message if you violate this convention.
• Policies are automatically aggregated under the hood. The convention is that aggregate outputs have the same name as the policy, just upper case.