Method and system for improving a placement of cells using energetic placement units alternating contraction and expansion operations
First Claim
1. A method for improving a placement of cells for an integrated circuit chip, comprising the steps of:
- (a) representing said cells as masses;
(b) representing interconnect nets between cells as springs such that each spring is connected between two of said masses;
(c) bringing said masses toward a minimum energy configuration by forces of said springs;
(d) moving said masses away from said minimum energy configuration; and
(e) repeatedly performing steps (c) and (d) until a predetermined criteria has been reached.
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Accused Products
Abstract
A method of cell placement for an integrated circuit chip includes performing a contraction operation by which at least some of the cells are relocated to new positions that provide lower interconnect wirelength. For each cell, the centroid of the net of cells to which the cell is connected is computed. The cell is then moved toward the centroid by a distance that is equal to the distance from the current position of the cell to the centroid multiplied by a "chaos" factor. This process continues until a specific energy condition is met; then the `expansion` mode is entered. An expansion operation is then performed by which the net force exerted on each cell by other cells in the placement and a resulting altered velocity of the cell are calculated, and a new cell position is calculated based on the altered velocity over an incremental length of time. The system stays in expansion mode until another energy criterion is met. The contraction and expansion modes are repeated in alternation, with the expansion operation preventing the cells from being undesirably converged by the contraction operation. At the start of each expansion operation, a normalization operation is performed to prevent skewing of the cells along a particular axis.
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Citations
31 Claims
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1. A method for improving a placement of cells for an integrated circuit chip, comprising the steps of:
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(a) representing said cells as masses; (b) representing interconnect nets between cells as springs such that each spring is connected between two of said masses; (c) bringing said masses toward a minimum energy configuration by forces of said springs; (d) moving said masses away from said minimum energy configuration; and (e) repeatedly performing steps (c) and (d) until a predetermined criteria has been reached. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method for improving an arrangement of masses and nets that interconnect the masses, comprising the steps of:
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(a) representing said nets as springs such that each spring is connected between two of said masses; (b) bringing said masses toward a minimum energy configuration by forces of said springs; (c) moving said masses away from said minimum energy configuration; and (d) repeatedly performing steps (b) and (c) until a predetermined criteria has been reached. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A physical design automation system for generating an optimized placement of cells for an integrated circuit chip, comprising:
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placement representation means for representing said cells as masses, and representing interconnect nets of said cells as springs such that each spring is connected between two of said masses; contraction means for bringing said masses toward a minimum energy configuration by forces of said springs; expansion means for propelling said masses away from said minimum energy configuration; and control means for controlling the contraction means and the expansion means to repeatedly perform said contraction operation and said expansion operation respectively until a predetermined criteria has been reached. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29, 30, 31)
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Specification