HSpice taking too much time to simulate (stopped at some point)

[srini.pes]

Hi to all
Am simulating one four bit ripple carry adder having four full adders.
In simulation, its taking too much time to respond (literally stopping at the fourth full adder).
When i remove one full adder and connect one half adder its working fine.
Please clarify this to me.
And here am giving the .sto file as a quick reference.

***** HSPICE -- C-2009.03-SP1 32-BIT (May 25 2009) winnt ******
Input File: c:\synopsys\hspice_c-2009.03-sp1\moscnt\adder_mos.sp
lic:
lic: FLEXlm: v8.5b
lic: USER: sridharan HOSTNAME: robolab-dellpc5
lic: HOSTID: 90b11c8bcf82 PID: 988
lic: Using FLEXlm license file:
lic: 2100@10.7.9.36
lic: Checkout 1 hspice
lic: License/Maintenance for hspice will expire on 31-dec-2020/2007.9
lic: NODE LOCKED license on hostid 90b11c8bcf82
lic:
Init: hspice initialization file: C:\synopsys\Hspice_C-2009.03-SP1\hspice.ini
init: begin read circuit files, cpu clock= 4.70E-02
option search = C:\synopsys\Hspice_C-2009.03-SP1\PARTS\behave\
option search = C:\synopsys\Hspice_C-2009.03-SP1\PARTS\AD\
option search = C:\synopsys\Hspice_C-2009.03-SP1\PARTS\XILINX\
option search = C:\synopsys\Hspice_C-2009.03-SP1\PARTS\TLINE\
option search = C:\synopsys\Hspice_C-2009.03-SP1\PARTS\TI\
option search = C:\synopsys\Hspice_C-2009.03-SP1\PARTS\SIGNET\
option search = C:\synopsys\Hspice_C-2009.03-SP1\PARTS\PCI\
option search = C:\synopsys\Hspice_C-2009.03-SP1\PARTS\LIN_TECH\
option search = C:\synopsys\Hspice_C-2009.03-SP1\PARTS\FET\
option search = C:\synopsys\Hspice_C-2009.03-SP1\PARTS\DIO\
option search = C:\synopsys\Hspice_C-2009.03-SP1\PARTS\COMLINE\
option search = C:\synopsys\Hspice_C-2009.03-SP1\PARTS\BURR_BRN\
option search = C:\synopsys\Hspice_C-2009.03-SP1\PARTS\BJT\
option search = C:\synopsys\Hspice_C-2009.03-SP1\PARTS\behave\
option search = C:\synopsys\Hspice_C-2009.03-SP1\PARTS\AD\
option post = 2.00
option runlvl
option method = gear
option post
option autost
option ingold = 2.00
option dcon = 1.00
option gshunt = 1.000E-12
option rmin = 1.000E-15
option abstol = 1.000E-05
option absvdc = 1.000E-04
option reltol = 1.000E-02
option relvdc = 1.000E-02
option numdgt = 4.00
option pivot = 1.00
option parhie = local
option epsmin = 1.000E-99
option expmax = 37.0
init: end read circuit files, cpu clock= 9.20E-02 memory= 392 kb
init: begin check errors, cpu clock= 9.20E-02
init: end check errors, cpu clock= 3.56E+00 memory= 64238 kb
init: begin setup matrix, pivot= 1 cpu clock= 3.56E+00
establish matrix -- done, cpu clock= 3.56E+00 memory= 66314 kb
re-order matrix -- done, cpu clock= 3.57E+00 memory= 66390 kb
init: end setup matrix, cpu clock= 3.57E+00 memory= 68638 kb
output: c:\synopsys\hspice_c-2009.03-sp1\moscnt\adder_mos.tr0
sweep: tran tran0 begin, stop_t= 1.00E-09 #sweeps= 101 cpu clock= 3.73E+00
tran: time= 1.1134E-10 tot_iter= 311 conv_iter= 61 cpu clock= 5.30E+01
tran: time= 2.0200E-10 tot_iter= 320 conv_iter= 65 cpu clock= 5.45E+01
tran: time= 3.0670E-10 tot_iter= 577 conv_iter= 139 cpu clock= 9.79E+01
tran: time= 4.0200E-10 tot_iter= 586 conv_iter= 143 cpu clock= 9.94E+01
tran: time= 5.0100E-10 tot_iter= 839 conv_iter= 213 cpu clock= 1.44E+02
tran: time= 6.0200E-10 tot_iter= 1221 conv_iter= 314 cpu clock= 2.12E+02
tran: time= 7.0100E-10 tot_iter= 1378 conv_iter= 359 cpu clock= 2.40E+0


Regards
SRINI