This node performs Directional Sampling to compute the probability of failure.
Directional Sampling generates random unit vectors instead of numbers. Along each direction, a line search is performed in order to find the zero root of the limit state function (the crossing point of the ray with the limit state hypersurface). The conditional failure probability for each direction is computed partial-analytically. The results for all individual directions are accumulated leading to a Monte-Carlo estimator of the probability of failure.
The number of required directions is independent of the magnitude of the probability of failure, but it grows with the number of involved random variables. The method is ideal if the limit state hypersurface is spherical in standard Gaussian space, and least effective if the limit state hypersurface is concave. The limit state should be unique in each direction. The mean values vector must not lie in the failure domain.
Further information about methods of reliability analysis used in optiSLang can be found here.
Initialization Options
To access the options shown in the following table, double-click the Directional Sampling system on the Scenery pane and switch to the Directional Sampling tab.
| Option | Description | ||
|---|---|---|---|
| Number of directions | Sets the total number of simulated directions. | ||
| Maximum number of parallel solver calls | Sets the number of directions calculated in parallel. | ||
| Line search phase | |||
| Number of parallel solver runs in presample | Sets the number of parallel solver runs during presample in line search. | ||
| Line search method | Sets the line search method. | ||
| Line search accuracy | Sets the maximum allowed distance to true limit state in standard-normal space. | ||
Additional Options
To access the options shown in the following table, in any tab, click .
| Option | Description |
|---|---|
| Limit maximum in parallel |
Controls the resource usage of nodes in the system. When the check box is cleared (default), a value is chosen to ensure the best possible utilization of the child nodes. When the check box is selected, set the value manually to specify how many designs are sent to child nodes, limiting the maximum degree of parallelism for all children. Ansys recommends keeping the check box clear. |
| Auto-save behavior |
Select one of the following options:
The project, including the database, is auto-saved (depending on defined interval) after calculating this node/system (either when the calculation succeeds or fails). By default, all parametric and algorithm systems have selected, all other nodes have selected. |