Round finger widths to grid.

compiler/pinv.py

@@ -6,6 +6,7 @@ from ptx import ptx
 from vector import vector
 from math import ceil
 from globals import OPTS
+from utils import round_to_grid
 
 class pinv(design.design):
     """
@@ -111,10 +112,13 @@ class pinv(design.design):
         # Recompute each mult width and check it isn't too small
         # This could happen if the height is narrow and the size is small
         # User should pick a bigger size to fix it...
-        self.nmos_width = self.nmos_width / self.tx_mults
+        # We also need to round the width to the grid or we will end up with LVS property
+        # mismatch errors when fingers are not a grid length and get rounded in the offset geometry.
+        self.nmos_width = round_to_grid(self.nmos_width / self.tx_mults)
         debug.check(self.nmos_width>=drc["minwidth_tx"],"Cannot finger NMOS transistors to fit cell height.")
-        self.pmos_width = self.pmos_width / self.tx_mults
-        debug.check(self.pmos_width>=drc["minwidth_tx"],"Cannot finger PMOS transistors to fit cell height.")        
+        self.pmos_width = round_to_grid(self.pmos_width / self.tx_mults)
+        debug.check(self.pmos_width>=drc["minwidth_tx"],"Cannot finger PMOS transistors to fit cell height.")
+        
 
     def setup_layout_constants(self):
         """

compiler/utils.py

@@ -7,20 +7,21 @@ from pin_layout import pin_layout
 
 OPTS = globals.OPTS
 
+def round_to_grid(number):
+    """
+    Rounds an arbitrary number to the grid.
+    """
+    grid = tech.drc["grid"]  
+    # this gets the nearest integer value
+    number_grid = int(round(round((number / grid), 2), 0))
+    number_off = number_grid * grid
+    return number_off
+
 def snap_to_grid(offset):
     """
     Changes the coodrinate to match the grid settings
     """
-    grid = tech.drc["grid"]  
-    x = offset[0]
-    y = offset[1]
-    # this gets the nearest integer value
-    xgrid = int(round(round((x / grid), 2), 0))
-    ygrid = int(round(round((y / grid), 2), 0))
-    xoff = xgrid * grid
-    yoff = ygrid * grid
-    out_offset = [xoff, yoff]
-    return out_offset
+    return [round_to_grid(offset[0]),round_to_grid(offset[1])]
 
 def pin_center(boundary):
     """