Analyzing Placement

After placement, you can view and analyze the results. You can report the area utilization with the report_placement_utilization cmd, the design timing with the report_timing cmd, the power consumption characterristics with the report_power command, and the QoR with the create_qor_snapshot command.

Placement Area Utilization

Placement area utilization, or simply "utilization", means the percentage of area avaiable for placement that is already occupied by placed cells. For Example, a utilization of 80 percent means that  80 percent of the available area is occupied by cells and 20 percent is empty can still be used for addtional cell placement, for movement of cells for legalization and optimization, or as an allowance to prevent excessive routing congestion.

You can report the utilization for part or all of the design with the
report_placement_utilization command:

report_placement_utilization
   [-non_fixed_only]
   [-grid_size  float]
   [-verbbose]
   [-coordinates  {x1 y1 x2  y2}]

For Example, to report the utilization of the rectangular area bounded by the corner points (340, 380) and (400, 450), you would use the following command:

icc_shell> report_placement_utilization -coordinates { 340 380 400 450 }
...
Std cell utilization :     84.02%  ( 2193/(2160-0),
                                     (std_cell_area/(region_area-blockage_area))
(Non-fixed + Fixed)
Std cell utilization:       77.68%     (1450/(2610-743))
...

If you do not specify the coordinates, the command reports the utilization of the whole chip.

In the reporting of utilization, there are two basic ways to consider the presence of standard cells that have fixed placement ("fixed standard cells"). These cells can be considered the same as unfixed cells, in other words, as cells occupying the available space. On the other hand, the space occupied by fixed cells can be considered unavailable space, in what is called a "non-fixed-only" utilization report.

Non-Fixed-Only Utilization Example:

Default Utilization (fixed and unfixed standard cells): 3/4 = 75 percent

Non-fixed-only standard cell utilization:  1/2 = 50 percent

The default utilization is reported to be 75 percent because 3/4 of the available area is occupied by standard cells. However, for non-fixed-only utilization reporting, the area occupied by fixed standard cells is considered unavailable, so the available area is two square units, occupied by one square unit of non-fixed standard cells, for a utilization of 1/2 or 50 percent.

Utilization reporting also considers the presence of placement blockages. For both default and non-fixed-only reporting, and part of the area occupied by a blockage is considered unavailable for placement. Thus, the default utilization is calculated as follows:

(non-fixed_standard_cell_area + fixed_standard_cell_area)/(total_area - blocked_area)

whereas non-fixed-only utilization is calculated as follows:

(non-fixed_standard_cell_area)/(total_area - fixed_standard_cell_area -blocked_area)

The report_placement_utilization command reports both the default and non-fixed-only utilization values. It also divides the specified region into subregions and separately reports the utilization within those subregions, to give an idea of the "evenness" of the utilization. By default, the subregion size is five times the placement site hight. You can specify a different subregion size, in microns, by using the -grid_size soon.

The -verbose option causes the reporting of the dimensions, locations, and individual utilization values of the subregions. Otherwise , the report shows only a summary listing of the number and percentage of subregions having different ranges of utilization values. The -non_fixed_only option specifies whether to use default or non-fixed-only utilization values for the subregion utilization report.