# Execution

Boulder Opal uses computational graphs to represent quantum systems for efficient simulations.

See the Understanding graphs in Boulder Opal topic and How to represent quantum systems using graphs user guide to learn more about computational graphs. The Choosing the approach to simulate a quantum system topic provides an overview of the different graph-based simulation options in Boulder Opal.

During graph execution, and depending on the size of your system, you can choose between eager and compiled modes for running your simulation. Learn more about how to best execute graph calculations in our Improving calculation performance in graphs topic.

## Classes

ExecutionMode | Configuration for the execution mode used in execute_graph. |

## Functions

execute_graph | Evaluate a graph corresponding to a set of generic functions. |