# Cuckoo Search

The Cuckoo Search is a very fast and efficient global optimization method, which is used in Slide2 for locating critical non-circular slip surfaces. It requires no user-input of trial surfaces or search objects.

In the Surface Options dialog, you may configure the following parameters for the Cuckoo Search:

• Initial Number of Surface Vertices
• Number of Surfaces to Store

The development of the Cuckoo Search algorithm used in Slide2 is documented in the following paper: Cuckoo Search Method in Slide2. It is highly recommended that you read this paper for further details on the Cuckoo Search parameters, its implementation in Slide2 and comparison with the Simulated Annealing search method.

## Initial Number of Surface Vertices

This is the initial number of vertices on each trial slip surface generated by the Cuckoo Search. During the Cuckoo Search algorithm and subsequent Optimization, the final number of vertices on a slip surface may differ from the initial number.

In general, the default value of 8 vertices is a good number to use. If this number is too small the true global minimum surface may not be located. If the number is too large, this may slow the computation without necessarily improving the final result. A rule of thumb is that the maximum value for the initial number of surface vertices, should not be more than half the Number of Slices defined in Project Settings.

## Number of Surfaces to Store

The Cuckoo Search uses the results of previously calculated slip surfaces to determine the generation of each new surface. The Number of Surfaces to Store represents the maximum number of previously calculated slip surface results which are stored in order to determine the next surface to compute. The default value of 1000 is recommended.

## Allow Surface with entrance and exit at the same elevation

In a typical slope stability problem, we usually avoid the generation of slip surfaces which have first and last points on the same elevation (e.g. slip surfaces on a horizontal surface). In some cases you may wish to calculate such surfaces, so you can select this checkbox to allow these surfaces to be analyzed by the Cuckoo Search.

## Convex Surfaces Only

See the Block Search topic for a description of the Convex Surfaces Only option.

## Optimize Surfaces

By default, the Optimize Surfaces option is enabled for Cuckoo Search. This applies an additional optimization to the minimum safety factor surface generated by the Cuckoo Search and usually results in a lower safety factor. It is recommended that this option is always enabled for a Cuckoo Search. See the Optimize Surfaces topic for details.

## Surface Filter

See the Surface Options topic for details about the Minimum Elevation, Minimum Depth, Minimum Area, Minimum Weight slip surface filter options.