Retrieving results¶
In this section, we describe how to get the results of a calculation after it has been parsed by AiiDA, or the input and output of a generic Node.
When a calculation is done on the remote computer, AiiDA will retrieve the results and try to parse the results with the default parser, if one is available for the given calculation. These results are stored in new nodes, and connected as output of the calculation. Of course, it is possible to directly check the output nodes for a given calculation and get their content. However, AiiDA provides a way to directly access the results, using the CalcJobResultManager
class, described in the next section.
The CalcJobResultManager¶
Prerequisites¶
Before getting the calculation results, we need a correctly finished and parsed
CalcJobNode
.
For example this can be a Quantum ESPRESSO pw.x
calculation.
You can load such a calculation – we’ll call it calc
– with the command
from aiida.orm import load_node
calc = load_node(YOURPK)
either in verdi shell
, or in a python script (as described here).
YOURPK
should be substituted by a valid calculation PK
in your database.
Using the CalcJobResultManager instance¶
Each CalcJobNode
has a res
attribute that is a
CalcJobResultManager
instance and
gives direct access to parsed data. You can access it as
calc.res
To get all the possible keys that were parsed, you can convert the instance into a list. For instance, if you type
print(list(calc.res))
you will get something like this:
['rho_cutoff', 'energy', 'energy_units', ...]
(the list of keys has been cut for clarity: you will get many more keys).
Once you know which keys have been parsed, you can access the parsed
value simply as an attribute of the res
CalcJobResultManager
. For instance, to get the final total energy, you can use
print(calc.res.energy)
that will print the total energy in units of eV, as also stated in the energy_units
key
print(calc.res.energy_units)
Similarly, you can get any other parsed value, for any code that provides a parser.
Hint
The CalcJobResultManager
is also integrated with the iPython/verdi shell completion mechanism: if calc
is a valid CalcJobNode
, you can type
calc.res.
and then press the TAB
key of the keyboard to get/complete the list of valid parsed properties for the calculation calc
.
Calculations and workflows inputs and outputs¶
In the following, we will show the methods to access the input and output nodes of a given calculation or workflow.
Again, we start by loading a node from the database. Unlike before, this can be any type of node.
For example, if we have a the node with PK
17:
from aiida.orm import load_node
calc = load_node(17)
Now, we want to find the nodes which have a direct input or output link to this node.
The node has several methods to extract this information: get_outgoing()
,
get_incoming()
.
The most practical way to access this information for a calculation (or workflow), when limiting solely to
INPUT_CALC
and CREATE
(or INPUT_WORK
and RETURN
, respectively), especially when working on the verdi shell
,
is by means of the .inputs
and .outputs
attributes.
The .inputs
attribute can be used to list and access the input nodes.
The names of the input links can be printed by list(calc.inputs)
or interactively by calc.inputs. + TAB
.
As an example, suppose that calc
has an input KpointsData
object under the linkname kpoints
. The command
calc.inputs.kpoints
returns the KpointsData
object.
Similarly the .outputs
attribute can be used to display the outputs of calc
.
Suppose that calc
has an output FolderData
with linkname retrieved
, then the command
calc.outputs.retrieved
returns the FolderData
object.