post_error_item index data_item_name data_item_index number

By means of this record, you can specify a data record for which the error in its value needs to be estimated.

The error is estimated as follows. The value for the data item will be remembered just before each mesh refinement (with control_mesh_refine_locally or control_mesh_refine_globally). The last 2 stored values and the current value are used create an estimated value . The error percentage is defined as:

$$100 ~ \frac{actual\_value ~-~ estimated\_value}{estimated\_value}$$

The percentage will be placed in the post_error_result, with the same index.

A typical example looks like:

...
post_error_item 1 -post_point_dof 1 -velx
...
control_mesh_refine_globally 10 ...
...
timesteps 20 ...
...
control_repeat_until_item 30 10 -value -post_error_result 1 0
control_repeat_until_tolerance 30 5.
...

This asks for the estimation of the error in the x-velocity at a point. It is used to determine automatically the number of refinements, by requiring that the error should become less than 5 percent.

A final remark. The values used for the error estimation will not be stored if the mesh refinement takes place at the start of the calculation, since that mesh contains normally not useful information.