# 8. External Loadstep Predictor

Warning

The external loadstep predictor is for implicit analyses only.

Production-ready loadstep predictor types are available in the Sierra/SM User Guide. The `LOADSTEP PREDICTOR` command block controls the behavior of the predictor that is used to predict the solution at the beginning of a new load step. This command block is placed in the `SOLVER` scope.

The `EXTERNAL`, `EXTERNAL_FIRST` and `TANGENT` predictor types are special use capabilities currently under development.

    BEGIN LOADSTEP PREDICTOR
      TYPE = <string>EXTERNAL|EXTERNAL_FIRST|TANGENT
    END [LOADSTEP PREDICTOR]

The tangent predictor is selected with the `TANGENT` option, which is useful in combination with the tangent preconditioner. This type of predictor uses the tangent preconditioner to estimate the next load step’s solution.

at new load steps. For instance, the external predictor file can come from the results output of a previous model run that included the command `OUTPUT EXTERNAL PREDICTOR VARIABLES` in the output block, i.e.:

    BEGIN RESULTS OUTPUT
      OUTPUT EXTERNAL PREDICTOR VARIABLES
    END [RESULTS OUTPUT]

If you would like to try the external predictor, please contact Sierra support for more information. at new load steps. For instance, the external predictor file can come from the results output of a previous model run that included the command `OUTPUT EXTERNAL PREDICTOR VARIABLES` in the output block, i.e.:

    BEGIN RESULTS OUTPUT
      OUTPUT EXTERNAL PREDICTOR VARIABLES
    END [RESULTS OUTPUT]

If you would like to try the external predictor, please contact Sierra support for more information.