Method of merging color sets of layout

A method comprising:

• determining one or more potential merges corresponding to a color set Ai and a color set Aj of N color sets, represented by A1 to AN, used in coloring polygons of a layout of an integrated circuit, N being a positive integer, i and j being integers from 1 to N, and i≠j;
• determining one or more potential cuts corresponding to the color set Ai and the second color set Aj;
• determining an index Aij according to the one or more potential merges and the one or more potential cuts, where Aij=Aji;
• based on the equation
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• for the color set Ai calculating, by a computer, a plurality of Ci, wherein index fi corresponds to the color set Ai, and index fj corresponds to the color set Aj;
• and
• based on the plurality of Ci, determining a color set configuration corresponding to a least number of polygons to be cut.

A method comprising:

• determining one or more potential merges between two sets of polygons of a layout, polygons of the two sets of polygons having corresponding coloring assignments, and each of the two sets of polygons being associated with a corresponding flipping index indicating if the corresponding coloring assignment is color-flipped;
• determining one or more potential cuts between the two sets of polygons;
• determining an index according to the one or more potential merges and the one or more potential cuts;
• calculating, by a computer, a plurality of parameters based on the index and various values of flipping indices of the two sets of polygons;
• selecting one of the plurality of parameters having the maximum value or the minimum value of the plurality of parameters;
• and
• merging the two sets of polygons according to the coloring assignments of the two sets of polygons and the values of the flipping indices of the two sets of polygons corresponding to the selected one of the plurality of parameters.