1. A computer-implemented method to identify a manufacturing problem area in a layout, the method comprising: performing, by computer, a model-based simulation for a first sample in the layout to obtain a first simulation-result which indicates whether a feature associated with the first sample in the layout is expected to have manufacturing problems; associating, in a database, the first sample with the first simulation-result; determining that a second sample in the layout, when oriented differently, is substantially similar to the first sample in the layout by: performing an exclusive-OR operation between the first sample and the second sample in a different orientation to obtain an exclusive-OR result, and determining whether the exclusive-OR result contains any polygons; and in response to determining that the second sample in the layout, when oriented differently, is substantially similar to the first sample in the layout, using the first simulation-result to determine whether a feature associated with the second sample in the layout is expected to have manufacturing problems.