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Cadence Skill - Totally Buggy?

cado

skill evaluates 0.142-0.142 as follows 

||(0.142 - 0.142)
||difference --> -5.273559e-16 
and 

if(0.142==0.142) as 

||(0.142 == 0.142)
||equal --> nil 

Is SKILL mad? 
 
min(1,2,3) gives you 1 

but make a list list1='(1,2,3) 

then min(list1) gives you => 

(1,2,3)! 

in SKILL -5.273559e-16 & 0 are the SAME!!! 

and 0.142 is not equal to 0.142!!! 
 
Could anyone try the following script and tell me about the problem?
 
cv=geGetEditCellView()
cell=cv~>cellName
wlist=list()
foreach(x cv~>shapes if(x~>lpp==list("M4" "drawing") then if(x~>width!=nil then wlist=cons(x~>width wlist) nwidth=mapw(x~>width)  
        printf("%s %f\n" "path width= " nwidth)          
        else
 bbx=x~>bBox
 ll=lowerLeft(bbx)
 ur=upperRight(bbx)
 lly=yCoord(ll)
 ury=yCoord(ur)
 llx=xCoord(ll)
 urx=xCoord(ur)
 lx=urx-llx
 ly=ury-lly
 width=min(lx,ly)
 wlist=cons(width wlist)
 nwidth=mapw(width)
 printf("%s %f\n" "Rectangle width= " nwidth)
) ;if x~>width!=nil
) ;if M4
) ; foreach shape
printf( "%s %s\n" "cell: " cell)

procedure(mapw(w)
mapwlist='(0.052,0.066,0.072,0.09,0.1,0.142,0.23)
prog(()
if(w>=0.7 then
 return(w)
 else
 match=0
 foreach(mpl mapwlist
  if(w==mpl then match++)
  )
  if(match>0 then return(w)
     else
     dlist=list()
     foreach(mpl mapwlist
      diff=abs(w-mpl)
      dlist=cons(diff dlist)
      )
       mindiff=()
       dls=0.0
       for(i 0 length(dlist)-1  dls=nth(i dlist)
      if(i!=0 then dlspre=nth(i-1 dlist)
         if(dls>dlspre then  mindiff=dlspre else mindiff=dls) else mindiff=dls)
         )    
     
      foreach(mpl mapwlist
       if(abs(w-mpl)==mindiff then
           return(mpl)
          )
            
      ) ;foreach mpl
      ) ;if match>0
      ) ;if w>0.7
      ) ;prog

)
Parents

  • There are indeed rounding errors in the code (try putting:

      printf("Original Width= %.16f\n" width)

    before the call to mapw(). However, that's not the real problem - it's the fact that your algorithm for finding mindiff is totally wrong! For a start, it's horrendously inefficient:

    1. You traverse the list once to check for an exact match
    2. You traverse the list again finding all the differences from w
    3. You use a for loop to traverse the difference list, using nth() to access each index - which in turn traverses the list from scratch. You should never use nth() within a for loop - that's what foreach is for. Otherwise it's O(N^2) - which is inefficient.
    4. You compare against nth(i-1 dlist) - so again traverse the list within the list - and find if the current difference is bigger than the previous difference - if it is, you set mindiff to be the previous difference. Can't see what purpose this is - it's going to give you the second to last difference in the list in this case (and since the list is reversed, this corresponds to the second entry in mapwlist, i.e. 0.066). A few printf's in the code show that it's getting things wrong.
    5. Then you traverse the list again checking the differences against the found mindiff to find which matches.

    So that's many traversals of the list (including list traversals within list traversals), and an incorrect algorithm. In addition, you should name your functions with a sensible prefix - there's a global name space, and Cadence uses functions with rather similar names - e.g. mapc, map, maplist, mapcar, mapcan - so there's a high risk of clashing with a Cadence function.

    You also should define the function before it's used...

    Anyway, here's a better (simpler and more efficient) implementation of "CADOmapw":

    procedure(CADOmapw(w)
  let((mapwlist mindiff closestw)
    mapwlist='(0.052,0.066,0.072,0.09,0.1,0.142,0.23)
    ;--------------------------------------------------------------------
    ; Return value of the if is the closest w
    ;--------------------------------------------------------------------
    if(w>=0.7 then
      w
    else
      foreach(mpw mapwlist
	delta=abs(w-mpw)
	when(!mindiff || delta<mindiff
	  closestw=mpw
	  mindiff=delta
	) ; when
      ) ; foreach
      closestw
    ) ; if
  ) ; let
) ; procedure

     

    Regards,

    Andrew.

Reply

  • There are indeed rounding errors in the code (try putting:

      printf("Original Width= %.16f\n" width)

    before the call to mapw(). However, that's not the real problem - it's the fact that your algorithm for finding mindiff is totally wrong! For a start, it's horrendously inefficient:

    1. You traverse the list once to check for an exact match
    2. You traverse the list again finding all the differences from w
    3. You use a for loop to traverse the difference list, using nth() to access each index - which in turn traverses the list from scratch. You should never use nth() within a for loop - that's what foreach is for. Otherwise it's O(N^2) - which is inefficient.
    4. You compare against nth(i-1 dlist) - so again traverse the list within the list - and find if the current difference is bigger than the previous difference - if it is, you set mindiff to be the previous difference. Can't see what purpose this is - it's going to give you the second to last difference in the list in this case (and since the list is reversed, this corresponds to the second entry in mapwlist, i.e. 0.066). A few printf's in the code show that it's getting things wrong.
    5. Then you traverse the list again checking the differences against the found mindiff to find which matches.

    So that's many traversals of the list (including list traversals within list traversals), and an incorrect algorithm. In addition, you should name your functions with a sensible prefix - there's a global name space, and Cadence uses functions with rather similar names - e.g. mapc, map, maplist, mapcar, mapcan - so there's a high risk of clashing with a Cadence function.

    You also should define the function before it's used...

    Anyway, here's a better (simpler and more efficient) implementation of "CADOmapw":

    procedure(CADOmapw(w)
  let((mapwlist mindiff closestw)
    mapwlist='(0.052,0.066,0.072,0.09,0.1,0.142,0.23)
    ;--------------------------------------------------------------------
    ; Return value of the if is the closest w
    ;--------------------------------------------------------------------
    if(w>=0.7 then
      w
    else
      foreach(mpw mapwlist
	delta=abs(w-mpw)
	when(!mindiff || delta<mindiff
	  closestw=mpw
	  mindiff=delta
	) ; when
      ) ; foreach
      closestw
    ) ; if
  ) ; let
) ; procedure

     

    Regards,

    Andrew.

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