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
CalculationResultManager class, described in the next section.
Before getting the calculation results, we need a correctly finished and parsed
JobCalculation. 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)
verdi shell, or in a python script (as described here).
YOURPK should be substituted by a valid calculation PK in your database.
Using the CalculationResultManager instance¶
To get all the possible keys that were parsed, you can convert the instance into a list. For instance, if you type
you will get something like this:
[u'rho_cutoff', u'energy', u'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
CalculationResultManager. For instance, to get the final total energy, you can use
that will print the total energy in units of eV, as also stated in the
Similarly, you can get any other parsed value, for any code that provides a parser.
and then press the TAB key of the keyboard to get/complete the list of valid parsed properties for the calculation
Node input and output¶
In the following, we will show the methods to access the input and output nodes of a given node.
Again, we start by loading a node from the database. Unlike before, this can be any type of node. For example, we can load the node with PK 17:
from aiida.orm import load_node node = load_node(17)
Now, we want to find the nodes which have a direct link to this node. The node has several methods to extract this information:
get_inputs_dict(). The most practical way to access this information, especially when working on the
verdi shell, is by means of the
inp attribute can be used to list and access the nodes with a direct link to
node in input. The names of the input links can be printed by
list(node.inp) or interactively by
node.inp. + TAB. As an example, suppose that
node has an input
KpointsData object under the linkname
kpoints. The command
out attribute can be used to display the names of links in output from
node and access these nodes. Suppose that
node has an output
FolderData with linkname
retrieved, then the command
For the input, there can be only one object for a given linkname. In contrast, there can be more than one output object with the same linkname. For example, a code object can be used by several calculations with the same linkname
code. For this reason, we append the string
_pk indicating the pk of the output code to the linkname. A linkname without
_pk still exists, and refers to the oldest link.
As an example, imagine that
node is a code, which is used by calculation #18 and #19. The linknames shown by
node.out. >> * code * code_18 * code_19
node.out.code_19 will return two different calculation objects, and
node.out.code will return the older one of the two.