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Adding Constraints to Tasks and Workflows GoToimage

Add constraints and execution directives to electrons by specifying them as arguments to the Covalent @electron decorator.

The most-used constraint is to explicitly name an executor for an electron. Other constraints are described in the API Reference.

Prerequisites​

Create a lattice.

import covalent as ct

@ct.electron
def sum(x, y):
    return x

@ct.electron
def square(x):
    return x * x

@ct.lattice
def sum_of_squares_wf(a, b):
    x2 = square(x=a)
    y2 = square(y=b)
    return sum(x=x2, y=y2)

Procedure​

  1. To specify a constraint on a single electron, add the constraint as a keyword argument to its Covalent @electron decorator.
@ct.electron(executor = "local")
def sum(x, y):
    return x
  1. To specify a constraint on all electrons in a lattice, add the constraint as a keyword argument to the @lattice decorator. The constraint is inherited by all electrons in the lattice.
@ct.lattice(executor = "local")
def sum_of_squares_wf(a, b):
    x2 = square(x=a)
    y2 = square(y=b)
    return sum(x=x2, y=y2)
  1. To override a constraint inherited from a lattice, specify the overriding constraint on the @electron decorator.
import covalent as ct

@ct.electron(executor = "dask")
def sum(x, y):
    return x

@ct.electron
def square(x):
    return x * x

@ct.lattice(executor = "local")
def sum_of_squares_wf(a, b):
    x2 = square(x=a)
    y2 = square(y=b)
    return sum(x=x2, y=y2)

In the example above, the square electron inherits the local executor from the lattice. The sum electron overrides the inherited value and uses the dask executor instead.

See Also​

Adding Pip Dependencies to an Electron

Adding Bash Dependencies to an Electron

Adding Callable Function Dependencies to an Electron