Trace number 3284203

Some explanations

A solver is run under the control of another program named runsolver. runsolver is in charge of imposing the CPU time limit and the memory limit to the solver. It also monitors some information about the process. The trace of the execution of a solver is divided into four (or five) parts:
  1. SOLVER DATA
    This is the output of the solver (stdout and stderr).
    Note that some very long lines in this section may be truncated by your web browser ! In such a case, you may want to use the "Download as text" link to get the trace as a text file.

    When the --timestamp option is passed to the runsolver program, each line output by the solver is prepended with a timestamp which indicates at what time the line was output by the solver. Times are relative to the start of the program, given in seconds. The first timestamp (if present) is estimated CPU time. The last timestamp is wall clock time.

    As some 'v lines' may be very long (sometimes several megabytes), the 'v line' output by your solver may be split on several lines to help limit the size of the trace recorded in the database. In any case, the exact output of your solver is preserved in a trace file.
  2. VERIFIER DATA
    The output of the solver is piped to a verifier program which will search a value line "v " and, if found, will check that the given interpretation satisfies all constraints.
  3. CONVERSION SCRIPT DATA (Optionnal)
    When a conversion script is used, this section shows the messages that were output by the conversion script.
  4. WATCHER DATA
    This is the informations gathered by the runsolver program. It first prints the different limits. There's a first limit on CPU time set to X seconds (see the parameters in the trace). After this time has ellapsed, runsolver sends a SIGTERM and 2 seconds later a SIGKILL to the solver. For safety, there's also another limit set to X+30 seconds which will send a SIGXPU to the solver. The last limit is on the virtual memory used by the process (see the parameters in the trace).
    Every ten seconds, the runsolver process fetches the content of /proc/loadavg, /proc/pid/stat and /proc/pid/statm (see man proc) and prints it as raw data. This is only recorded in case we need to investigate the behaviour of a solver. The memory used by the solver (vsize) is also given every ten seconds.
    When the solver exits, runsolver prints some informations such as status and time. CPU usage is the ratio CPU Time/Real Time.
  5. LAUNCHER DATA
    These informations are related to the script which will launch the solver. The most important informations are the command line given to the solver, the md5sum of the different files and the dump of the /proc/cpuinfo and /proc/meminfo which provides some useful information on the computer.

Solver answer on this benchmark

Solver NameAnswerCPU timeWall clock time
glueminisat 2.2.5UNSAT 27.7898 27.7904

General information on the benchmark

Namevelev-pipe-o-uns-1.1-6.cnf
MD5SUMd986f0b849e7c714ed5d3a26373567af
Bench CategoryAPPLICATION (applications instances)
Best result obtained on this benchmarkUNSAT
Best CPU time to get the best result obtained on this benchmark12.6861
Satisfiable
(Un)Satisfiability was proved
Number of variables17710
Number of clauses304026
Sum of the clauses size890580
Maximum clause length131
Minimum clause length1
Number of clauses of size 11
Number of clauses of size 2268354
Number of clauses of size 326401
Number of clauses of size 4173
Number of clauses of size 5120
Number of clauses of size over 58977

Solver Data

27.69/27.78	WARNING: for repeatability, setting FPU to use double precision
27.69/27.78	s UNSATISFIABLE

Verifier Data

No possible verification on an UNSAT instance

Watcher Data

runsolver Copyright (C) 2010-2011 Olivier ROUSSEL

This is runsolver version 3.3.0 (svn: 935)

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

command line: BIN/runsolver --timestamp -w /tmp/evaluation-result-3284203-1303761087/watcher-3284203-1303761087 -o /tmp/evaluation-result-3284203-1303761087/solver-3284203-1303761087 -C 2400 -W 1300 -M 7680 glueminisat -compe HOME/instance-3284203-1303761087.cnf 

running on 2 cores: 4,6

Enforcing CPUTime limit (soft limit, will send SIGTERM then SIGKILL): 2400 seconds
Enforcing CPUTime limit (hard limit, will send SIGXCPU): 2430 seconds
Enforcing wall clock limit (soft limit, will send SIGTERM then SIGKILL): 1300 seconds
Enforcing VSIZE limit (soft limit, will send SIGTERM then SIGKILL): 7864320 KiB
Enforcing VSIZE limit (hard limit, stack expansion will fail with SIGSEGV, brk() and mmap() will return ENOMEM): 7915520 KiB
Current StackSize limit: 10240 KiB


[startup+0 s]
/proc/loadavg: 4.10 3.88 3.35 5/193 9016
/proc/meminfo: memFree=13594240/32951124 swapFree=67111528/67111528
[pid=9016] ppid=9014 vsize=19812 CPUtime=0 cores=4,6
/proc/9016/stat : 9016 (glueminisat) R 9014 9016 8720 0 -1 4202496 797 0 0 0 0 0 0 0 25 0 1 0 487706621 20287488 728 33554432000 4194304 4309791 140734492399328 18446744073709551615 4245417 0 0 4096 8388610 0 0 0 17 4 0 0 0
/proc/9016/statm: 4953 729 215 29 0 1582 0

[startup+0.0777269 s]
/proc/loadavg: 4.10 3.88 3.35 5/193 9016
/proc/meminfo: memFree=13594240/32951124 swapFree=67111528/67111528
[pid=9016] ppid=9014 vsize=29972 CPUtime=0.07 cores=4,6
/proc/9016/stat : 9016 (glueminisat) R 9014 9016 8720 0 -1 4202496 4694 0 0 0 6 1 0 0 25 0 1 0 487706621 30691328 4100 33554432000 4194304 4309791 140734492399328 18446744073709551615 4294433 0 0 4096 8388610 0 0 0 17 4 0 0 0
/proc/9016/statm: 7493 4101 217 29 0 4122 0
Current children cumulated CPU time (s) 0.07
Current children cumulated vsize (KiB) 29972

[startup+0.100736 s]
/proc/loadavg: 4.10 3.88 3.35 5/193 9016
/proc/meminfo: memFree=13594240/32951124 swapFree=67111528/67111528
[pid=9016] ppid=9014 vsize=35580 CPUtime=0.09 cores=4,6
/proc/9016/stat : 9016 (glueminisat) R 9014 9016 8720 0 -1 4202496 6002 0 0 0 8 1 0 0 25 0 1 0 487706621 36433920 5149 33554432000 4194304 4309791 140734492399328 18446744073709551615 255376998155 0 0 4096 8388610 0 0 0 17 4 0 0 0
/proc/9016/statm: 8895 5150 217 29 0 5524 0
Current children cumulated CPU time (s) 0.09
Current children cumulated vsize (KiB) 35580

[startup+0.300682 s]
/proc/loadavg: 4.10 3.88 3.35 5/193 9016
/proc/meminfo: memFree=13594240/32951124 swapFree=67111528/67111528
[pid=9016] ppid=9014 vsize=38940 CPUtime=0.29 cores=4,6
/proc/9016/stat : 9016 (glueminisat) R 9014 9016 8720 0 -1 4202496 7055 0 0 0 28 1 0 0 25 0 1 0 487706621 39874560 6148 33554432000 4194304 4309791 140734492399328 18446744073709551615 4236751 0 0 4096 8388610 0 0 0 17 4 0 0 0
/proc/9016/statm: 9735 6149 225 29 0 6364 0
Current children cumulated CPU time (s) 0.29
Current children cumulated vsize (KiB) 38940

[startup+0.700609 s]
/proc/loadavg: 4.10 3.88 3.35 5/193 9016
/proc/meminfo: memFree=13594240/32951124 swapFree=67111528/67111528
[pid=9016] ppid=9014 vsize=38996 CPUtime=0.69 cores=4,6
/proc/9016/stat : 9016 (glueminisat) R 9014 9016 8720 0 -1 4202496 9127 0 0 0 68 1 0 0 25 0 1 0 487706621 39931904 5903 33554432000 4194304 4309791 140734492399328 18446744073709551615 4253890 0 0 4096 8388610 0 0 0 17 4 0 0 0
/proc/9016/statm: 9749 5903 244 29 0 6378 0
Current children cumulated CPU time (s) 0.69
Current children cumulated vsize (KiB) 38996

[startup+1.50044 s]
/proc/loadavg: 4.10 3.88 3.35 5/194 9017
/proc/meminfo: memFree=13568820/32951124 swapFree=67111528/67111528
[pid=9016] ppid=9014 vsize=43416 CPUtime=1.49 cores=4,6
/proc/9016/stat : 9016 (glueminisat) R 9014 9016 8720 0 -1 4202496 9922 0 0 0 148 1 0 0 25 0 1 0 487706621 44457984 6685 33554432000 4194304 4309791 140734492399328 18446744073709551615 4276015 0 0 4096 8388610 0 0 0 17 4 0 0 0
/proc/9016/statm: 10854 6685 245 29 0 7483 0
Current children cumulated CPU time (s) 1.49
Current children cumulated vsize (KiB) 43416

[startup+3.10114 s]
/proc/loadavg: 4.17 3.90 3.36 5/194 9017
/proc/meminfo: memFree=13562744/32951124 swapFree=67111528/67111528
[pid=9016] ppid=9014 vsize=43416 CPUtime=3.09 cores=4,6
/proc/9016/stat : 9016 (glueminisat) R 9014 9016 8720 0 -1 4202496 13838 0 0 0 307 2 0 0 25 0 1 0 487706621 44457984 7268 33554432000 4194304 4309791 140734492399328 18446744073709551615 4259106 0 0 4096 8388610 0 0 0 17 4 0 0 0
/proc/9016/statm: 10854 7268 245 29 0 7483 0
Current children cumulated CPU time (s) 3.09
Current children cumulated vsize (KiB) 43416

[startup+6.30058 s]
/proc/loadavg: 4.17 3.90 3.36 5/194 9017
/proc/meminfo: memFree=13578492/32951124 swapFree=67111528/67111528
[pid=9016] ppid=9014 vsize=63156 CPUtime=6.29 cores=4,6
/proc/9016/stat : 9016 (glueminisat) R 9014 9016 8720 0 -1 4202496 22652 0 0 0 626 3 0 0 25 0 1 0 487706621 64671744 11626 33554432000 4194304 4309791 140734492399328 18446744073709551615 4253720 0 0 4096 8388610 0 0 0 17 4 0 0 0
/proc/9016/statm: 15789 11626 245 29 0 12418 0
Current children cumulated CPU time (s) 6.29
Current children cumulated vsize (KiB) 63156

[startup+12.7004 s]
/proc/loadavg: 4.14 3.90 3.37 5/194 9017
/proc/meminfo: memFree=13601580/32951124 swapFree=67111528/67111528
[pid=9016] ppid=9014 vsize=74648 CPUtime=12.69 cores=4,6
/proc/9016/stat : 9016 (glueminisat) R 9014 9016 8720 0 -1 4202496 32560 0 0 0 1264 5 0 0 25 0 1 0 487706621 76439552 15326 33554432000 4194304 4309791 140734492399328 18446744073709551615 4277548 0 0 4096 8388610 0 0 0 17 4 0 0 0
/proc/9016/statm: 18662 15326 245 29 0 15291 0
Current children cumulated CPU time (s) 12.69
Current children cumulated vsize (KiB) 74648

[startup+25.501 s]
/proc/loadavg: 4.12 3.90 3.37 5/194 9018
/proc/meminfo: memFree=13557932/32951124 swapFree=67111528/67111528
[pid=9016] ppid=9014 vsize=93504 CPUtime=25.49 cores=4,6
/proc/9016/stat : 9016 (glueminisat) R 9014 9016 8720 0 -1 4202496 36530 0 0 0 2544 5 0 0 25 0 1 0 487706621 95748096 18964 33554432000 4194304 4309791 140734492399328 18446744073709551615 4259224 0 0 4096 8388610 0 0 0 17 4 0 0 0
/proc/9016/statm: 23376 18964 245 29 0 20005 0
Current children cumulated CPU time (s) 25.49
Current children cumulated vsize (KiB) 93504

Solver just ended. Dumping a history of the last processes samples

[startup+27.1007 s]
/proc/loadavg: 4.11 3.90 3.37 5/194 9018
/proc/meminfo: memFree=13554832/32951124 swapFree=67111528/67111528
[pid=9016] ppid=9014 vsize=93504 CPUtime=27.09 cores=4,6
/proc/9016/stat : 9016 (glueminisat) R 9014 9016 8720 0 -1 4202496 37306 0 0 0 2704 5 0 0 25 0 1 0 487706621 95748096 19720 33554432000 4194304 4309791 140734492399328 18446744073709551615 4259441 0 0 4096 8388610 0 0 0 17 4 0 0 0
/proc/9016/statm: 23376 19720 245 29 0 20005 0
Current children cumulated CPU time (s) 27.09
Current children cumulated vsize (KiB) 93504

[startup+27.5067 s]
/proc/loadavg: 4.11 3.90 3.37 5/194 9018
/proc/meminfo: memFree=13551856/32951124 swapFree=67111528/67111528
[pid=9016] ppid=9014 vsize=93504 CPUtime=27.49 cores=4,6
/proc/9016/stat : 9016 (glueminisat) R 9014 9016 8720 0 -1 4202496 37518 0 0 0 2744 5 0 0 25 0 1 0 487706621 95748096 19927 33554432000 4194304 4309791 140734492399328 18446744073709551615 4253853 0 0 4096 8388610 0 0 0 17 4 0 0 0
/proc/9016/statm: 23376 19927 245 29 0 20005 0
Current children cumulated CPU time (s) 27.49
Current children cumulated vsize (KiB) 93504

[startup+27.7006 s]
/proc/loadavg: 4.11 3.90 3.37 5/194 9018
/proc/meminfo: memFree=13551856/32951124 swapFree=67111528/67111528
[pid=9016] ppid=9014 vsize=93504 CPUtime=27.69 cores=4,6
/proc/9016/stat : 9016 (glueminisat) R 9014 9016 8720 0 -1 4202496 37571 0 0 0 2764 5 0 0 25 0 1 0 487706621 95748096 19977 33554432000 4194304 4309791 140734492399328 18446744073709551615 4260191 0 0 4096 8388610 0 0 0 17 4 0 0 0
/proc/9016/statm: 23376 19977 245 29 0 20005 0
Current children cumulated CPU time (s) 27.69
Current children cumulated vsize (KiB) 93504

Child status: 20
Real time (s): 27.7904
CPU time (s): 27.7898
CPU user time (s): 27.7268
CPU system time (s): 0.06299
CPU usage (%): 99.9979
Max. virtual memory (cumulated for all children) (KiB): 105000

getrusage(RUSAGE_CHILDREN,...) data:
user time used= 27.7268
system time used= 0.06299
maximum resident set size= 0
integral shared memory size= 0
integral unshared data size= 0
integral unshared stack size= 0
page reclaims= 37576
page faults= 0
swaps= 0
block input operations= 0
block output operations= 0
messages sent= 0
messages received= 0
signals received= 0
voluntary context switches= 7
involuntary context switches= 306

runsolver used 0.050992 second user time and 0.106983 second system time

The end

Launcher Data

Begin job on node135 at 2011-04-25 21:51:28
IDJOB=3284203
IDBENCH=71718
IDSOLVER=1650
FILE ID=node135/3284203-1303761087
RUNJOBID= node135-1303760327-8739
PBS_JOBID= 13157148
Free space on /tmp= 71244 MiB

SOLVER NAME= glueminisat 2.2.5
BENCH NAME= SAT_RACE06/velev-pipe-o-uns-1.1-6.cnf
COMMAND LINE= glueminisat -compe BENCHNAME
RUNSOLVER COMMAND LINE= BIN/runsolver --timestamp -w /tmp/evaluation-result-3284203-1303761087/watcher-3284203-1303761087 -o /tmp/evaluation-result-3284203-1303761087/solver-3284203-1303761087 -C 2400 -W 1300 -M 7680  glueminisat -compe HOME/instance-3284203-1303761087.cnf

TIME LIMIT= 2400 seconds
MEMORY LIMIT= 7680 MiB
NBCORE= 2

MD5SUM BENCH= d986f0b849e7c714ed5d3a26373567af
RANDOM SEED=1051653656

node135.alineos.net Linux 2.6.18-164.el5 #1 SMP Thu Sep 3 03:28:30 EDT 2009

/proc/cpuinfo:
processor	: 0
vendor_id	: GenuineIntel
cpu family	: 6
model		: 26
model name	: Intel(R) Xeon(R) CPU           X5550  @ 2.67GHz
stepping	: 5
cpu MHz		: 2666.851
cache size	: 8192 KB
physical id	: 0
siblings	: 4
core id		: 0
cpu cores	: 4
apicid		: 0
fpu		: yes
fpu_exception	: yes
cpuid level	: 11
wp		: yes
flags		: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm syscall nx rdtscp lm constant_tsc ida nonstop_tsc pni monitor ds_cpl vmx est tm2 cx16 xtpr popcnt lahf_lm
bogomips	: 5333.70
clflush size	: 64
cache_alignment	: 64
address sizes	: 40 bits physical, 48 bits virtual
power management: [8]

processor	: 1
vendor_id	: GenuineIntel
cpu family	: 6
model		: 26
model name	: Intel(R) Xeon(R) CPU           X5550  @ 2.67GHz
stepping	: 5
cpu MHz		: 2666.851
cache size	: 8192 KB
physical id	: 1
siblings	: 4
core id		: 0
cpu cores	: 4
apicid		: 16
fpu		: yes
fpu_exception	: yes
cpuid level	: 11
wp		: yes
flags		: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm syscall nx rdtscp lm constant_tsc ida nonstop_tsc pni monitor ds_cpl vmx est tm2 cx16 xtpr popcnt lahf_lm
bogomips	: 5332.83
clflush size	: 64
cache_alignment	: 64
address sizes	: 40 bits physical, 48 bits virtual
power management: [8]

processor	: 2
vendor_id	: GenuineIntel
cpu family	: 6
model		: 26
model name	: Intel(R) Xeon(R) CPU           X5550  @ 2.67GHz
stepping	: 5
cpu MHz		: 2666.851
cache size	: 8192 KB
physical id	: 0
siblings	: 4
core id		: 1
cpu cores	: 4
apicid		: 2
fpu		: yes
fpu_exception	: yes
cpuid level	: 11
wp		: yes
flags		: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm syscall nx rdtscp lm constant_tsc ida nonstop_tsc pni monitor ds_cpl vmx est tm2 cx16 xtpr popcnt lahf_lm
bogomips	: 5332.75
clflush size	: 64
cache_alignment	: 64
address sizes	: 40 bits physical, 48 bits virtual
power management: [8]

processor	: 3
vendor_id	: GenuineIntel
cpu family	: 6
model		: 26
model name	: Intel(R) Xeon(R) CPU           X5550  @ 2.67GHz
stepping	: 5
cpu MHz		: 2666.851
cache size	: 8192 KB
physical id	: 1
siblings	: 4
core id		: 1
cpu cores	: 4
apicid		: 18
fpu		: yes
fpu_exception	: yes
cpuid level	: 11
wp		: yes
flags		: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm syscall nx rdtscp lm constant_tsc ida nonstop_tsc pni monitor ds_cpl vmx est tm2 cx16 xtpr popcnt lahf_lm
bogomips	: 6640.14
clflush size	: 64
cache_alignment	: 64
address sizes	: 40 bits physical, 48 bits virtual
power management: [8]

processor	: 4
vendor_id	: GenuineIntel
cpu family	: 6
model		: 26
model name	: Intel(R) Xeon(R) CPU           X5550  @ 2.67GHz
stepping	: 5
cpu MHz		: 2666.851
cache size	: 8192 KB
physical id	: 0
siblings	: 4
core id		: 2
cpu cores	: 4
apicid		: 4
fpu		: yes
fpu_exception	: yes
cpuid level	: 11
wp		: yes
flags		: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm syscall nx rdtscp lm constant_tsc ida nonstop_tsc pni monitor ds_cpl vmx est tm2 cx16 xtpr popcnt lahf_lm
bogomips	: 5332.78
clflush size	: 64
cache_alignment	: 64
address sizes	: 40 bits physical, 48 bits virtual
power management: [8]

processor	: 5
vendor_id	: GenuineIntel
cpu family	: 6
model		: 26
model name	: Intel(R) Xeon(R) CPU           X5550  @ 2.67GHz
stepping	: 5
cpu MHz		: 2666.851
cache size	: 8192 KB
physical id	: 1
siblings	: 4
core id		: 2
cpu cores	: 4
apicid		: 20
fpu		: yes
fpu_exception	: yes
cpuid level	: 11
wp		: yes
flags		: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm syscall nx rdtscp lm constant_tsc ida nonstop_tsc pni monitor ds_cpl vmx est tm2 cx16 xtpr popcnt lahf_lm
bogomips	: 5332.75
clflush size	: 64
cache_alignment	: 64
address sizes	: 40 bits physical, 48 bits virtual
power management: [8]

processor	: 6
vendor_id	: GenuineIntel
cpu family	: 6
model		: 26
model name	: Intel(R) Xeon(R) CPU           X5550  @ 2.67GHz
stepping	: 5
cpu MHz		: 2666.851
cache size	: 8192 KB
physical id	: 0
siblings	: 4
core id		: 3
cpu cores	: 4
apicid		: 6
fpu		: yes
fpu_exception	: yes
cpuid level	: 11
wp		: yes
flags		: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm syscall nx rdtscp lm constant_tsc ida nonstop_tsc pni monitor ds_cpl vmx est tm2 cx16 xtpr popcnt lahf_lm
bogomips	: 5332.74
clflush size	: 64
cache_alignment	: 64
address sizes	: 40 bits physical, 48 bits virtual
power management: [8]

processor	: 7
vendor_id	: GenuineIntel
cpu family	: 6
model		: 26
model name	: Intel(R) Xeon(R) CPU           X5550  @ 2.67GHz
stepping	: 5
cpu MHz		: 2666.851
cache size	: 8192 KB
physical id	: 1
siblings	: 4
core id		: 3
cpu cores	: 4
apicid		: 22
fpu		: yes
fpu_exception	: yes
cpuid level	: 11
wp		: yes
flags		: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm syscall nx rdtscp lm constant_tsc ida nonstop_tsc pni monitor ds_cpl vmx est tm2 cx16 xtpr popcnt lahf_lm
bogomips	: 5332.76
clflush size	: 64
cache_alignment	: 64
address sizes	: 40 bits physical, 48 bits virtual
power management: [8]


/proc/meminfo:
MemTotal:     32951124 kB
MemFree:      13594520 kB
Buffers:       2067728 kB
Cached:       16270312 kB
SwapCached:          0 kB
Active:        7955904 kB
Inactive:     10803440 kB
HighTotal:           0 kB
HighFree:            0 kB
LowTotal:     32951124 kB
LowFree:      13594520 kB
SwapTotal:    67111528 kB
SwapFree:     67111528 kB
Dirty:            5984 kB
Writeback:         164 kB
AnonPages:      420500 kB
Mapped:          15448 kB
Slab:           532624 kB
PageTables:       6252 kB
NFS_Unstable:        0 kB
Bounce:              0 kB
CommitLimit:  83587088 kB
Committed_AS:   639760 kB
VmallocTotal: 34359738367 kB
VmallocUsed:     33868 kB
VmallocChunk: 34359703231 kB
HugePages_Total:     0
HugePages_Free:      0
HugePages_Rsvd:      0
Hugepagesize:     2048 kB

Free space on /tmp at the end= 71244 MiB
End job on node135 at 2011-04-25 21:51:55