icc 的place_opt中出现了displacement

djim2002

小弟刚学ICC，有一些问题想请教：
如下：
There were 138 more cells with legal displacements larger than 5 rows.
Initial legalization:  100% (18 sec)
Optimizations pass 1: 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% (46.7 sec)
Optimizations pass 2: 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% (45.6 sec)
Optimizations pass 3: 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% (44.8 sec)
Warning: Found cells with large displacements during legalization. If the
    cells with large displacements are timing critical these displacements
    may cause problems. Please see the following plots for details.
    The 'max_displacements' plot shows the design with blockages in green
    and the legalized cells with the largest displacements drawn
    with red displacement vectors.
    The 'colored_displacements' plot shows the design with blockages in green
    and with placed cells colored according to their displacements.
    The mapping of colors to displacements can be seen in the
    legend in the lower right.
。。。。。。。。。。。。。。。。。
。。。。。。。。。。。。。。。。。
avg cell displacement:    0.209 um ( 0.36 row height)
max cell displacement:   79.815 um (138.57 row height)
std deviation:            1.040 um ( 1.80 row height)
number of cell moved:   1179408 cells (out of 1179434 cells)
Largest displacement cells:
  Cell: */gen_U1/mem/u_rep/u_tile/dIb2508 (BUFX4B)
    Input location: (977.361 990.440)
    Legal location: (1055.970 1004.264)
    Displacement: 79.815 um, e.g. 138.57 row height.
  Cell: */dIb2132 (BUFX4B)
    Input location: (978.783 989.864)
    Legal location: (1055.970 977.192)
    Displacement: 78.220 um, e.g. 135.80 row height.

这个displacement是什么意思啊？

damonzhao

Largest displacement cells:
  Cell: */gen_U1/mem/u_rep/u_tile/dIb2508 (BUFX4B)
    Input location: (977.361 990.440)
    Legal location: (1055.970 1004.264)
    Displacement: 79.815 um, e.g. 138.57 row height.
  Cell: */dIb2132 (BUFX4B)
    Input location: (978.783 989.864)
    Legal location: (1055.970 977.192)
    Displacement: 78.220 um, e.g. 135.80 row height.

定位一下看看呢

小干爹z2z

在legalize_placement 中location 移动最大的cell
我想是为了表明这些cell在optimization的时候放在这个位置得到比较好的结果
但是legalization的时候移动了，工具给你报出最大的location改变，以便user定位是否在这些cell上有timing drc问题是因为legalization的原因而不是optimization的原因
Input的legalization之前的location
一顿瞎说，不代表本台立场

djim2002

有点道理

reddamm

这个应该是工具做优化时，增加的BUFFER没地方，工具做了尝试，但是还是放不下出的报告。

nature19900303

尝试在floorplan是增加面积看看。