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# statistics(?Keyword, -Value)

Succeeds if the statistics item Keyword has value Value.

Keyword
  Atom or Variable.
Value
  Prolog term.

## Description

Used to retrieve various statistical information about the running ECLiPSe . To print a list of all the current values, statistics/0 can be used.

The following list details the statistic items:

control_stack_allocated

  Unit : bytes

  Description : The amount of control stack currently allocated. The control stack is allocated in chunks, up to a maximum controlled by the -l command line option. The local and control stacks share the same memory area specified by the -l option, which thus gives the maximum combined allocated size of these two stacks.

control_stack_peak

  Unit : bytes

  Description : The peak allocated size of the control stack during this session. Chunks of memory can be allocated to, and deallocated from, the control stack as it grows and shrinks.

control_stack_used

  Unit : bytes

  Description : The amount of control stack currently in use. This stack holds information needed for backtracking.

cputime

  Unit : seconds (float)

  Description : Returns the cpu time of the calling thread, the same as cputime/1.

dictionary_entries

  Unit : count

  Description : The number of atoms and functors that are currently known to the system. This is equal to the number of solutions that current_functor/1 would return.

dict_hash_usage

  Type : pair of integers Used/Avail

  Description : Returns two numbers: the number of actually used slots in the dictionary hash table, versus the number of available slots.

dict_hash_collisions

  Type : pair of integers Collisions/Entries

  Description : Returns two numbers: the number of dictionary entries that collided with existing hash table entries, versus the total number of dictionary hash table entries.

dict_gc_number

  Unit : count

  Description : The number of dictionary garbage collections performed during this session.

dict_gc_countdown

  Unit : count

  Description : The number of new dictionary entries that can be created before the next dictionary garbage collection is triggered.

dict_gc_running

  Unit : atomic constant 'false' or 'true'

  Description : When 'true', a dictionary garbage collection is currently under way. This can occur in applications with multiple engine threads, while some engines have not yet finished (or are prevented from performing) their share of garbage collection activity.

event_time

  Unit : seconds (float)

  Description : Returns the elapsed real time (session_time) or the elapsed user time (cputime) since the start of a (parallel) ECLiPSe session depending on the value of the after_event_timer flag.

gc_area

  Unit : bytes

  Description : The average area processed by a garbage collection. This number should be close to the value of gc_interval. If it is much higher, gc_interval should be increased.

gc_collected

  Unit : bytes (float)

  Description : The total number of bytes collected in the global stack during all the garbage collections in this session. This value is a float, to avoid overflow.

gc_number

  Unit : count

  Description : The number of global/trail stack garbage collections performed during this session.

gc_ratio

  Unit : percent (float)

  Description : The average percentage of garbage found and collected in the garbage collections performed so far. If this number is low, gc_interval should be increased.

gc_time

  Unit : seconds (float)

  Description : The total time spent for all garbage collections in this session.

private_heap_allocated

  Unit : bytes

  Description : The amount of memory assigned to the private heap. This area will never shrink.

private_heap_used

  Unit : bytes

  Description : The amount of memory currently used for private data.

global_stack_allocated

  Unit : bytes

  Description : The amount of global stack currently allocated. The global stack is allocated in chunks, up to a maximum controlled by the -g command line option. The global stack and trail share the same memory area specified by the -g option, which thus gives the maximum possible combined allocated size of these two stacks.

global_stack_peak

  Unit : bytes

  Description : The peak allocated size of the global stack during this session. Chunks of memory can be allocated to, and deallocated from, the global stack as it grows and shrinks.

global_stack_used

  Unit : bytes

  Description : The amount of global stack currently in use. The global stack holds lists and structures and is subject to garbage collection.

hr_time

  Unit : seconds (float)

  Description : Returns the value of a high-resolution timer in seconds. The precise meaning of this value is operating system and hardware dependent, but the resolution should be better than the other time statistics, usually in the microsecond range. Only the difference between two such times is meaningful, the absolute value does not have any specific meaning. If operating system or hardware do not provide such a timer, the value is the same as session_time.

local_stack_allocated

  Unit : bytes

  Description : The amount of local stack currently allocated. The local stack is allocated in chunks, up to a maximum controlled by the -l command line option. The local and control stacks share the same memory area specified by the -l option, which thus gives the maximum combined allocated size of these two stacks.

local_stack_peak

  Unit : bytes

  Description : The peak allocated size of the local stack during this session. Chunks of memory can be allocated to, and deallocated from, the local stack as it grows and shrinks.

local_stack_used

  Unit : bytes

  Description : The amount of local stack currently in use. This stack holds Prolog variables and return addresses.

global_stack

  Unit : List of bytes

  Description : Returns a list of two numbers for the allocated global stack: the number of bytes currently used, and the number of bytes currently free. It is provided mainly for compatibility.

local_stack

  Unit : List of bytes

  Description : Returns a list of two numbers on the current usage of the allocated local and control stacks. In the original WAM, these two stacks are combined into a single stack. This is provided for compatibility purposes only.

trail

  Unit : List of bytes

  Description : Returns a list of two numbers for the allocated trail: the number of bytes currently used, and the number of bytes currently free. It is provided mainly for compatibility.

runtime

  Unit : List of milliseconds (integers)

  Description : Returns a list of two times: user cpu time since the start of the ECLiPSe session, user cpu time since the last call to statistics(runtime, _). As from ECLiPSe 4.2, these times exclude the time spent in garbage collection. This item is provided primarily for compatibility reasons.

session_time

  Unit : seconds (float)

  Description : Returns the real time elapsed since the start of a (parallel) ECLiPSe session. This is the only timer that can be reliably used in a parallel execution, since it accesses a central clock. All other timers are local to the worker where they are accessed.

shared_heap_allocated

  Unit : bytes

  Description : The amount of memory assigned to the code heap, i.e. the area used for storing compiled Prolog code, atoms, records, non-logical variables, descriptors, buffers etc. This area will never shrink.

shared_heap_used

  Unit : bytes

  Description : The amount of memory currently used for compiled Prolog code, atoms, records, non-logical variables, descriptors, buffers etc.

times

  Unit : List of seconds (floats)

  Description : Returns a list of three times: user cpu time, system cpu time and real time elapsed since the start of the ECLiPSe session. The cpu times are for the whole process, i.e. all threads together. Therefore, in multithreaded programs, process cpu time can be much higher than elapsed real time. For thread cpu time, see statistics(cputime,T) and cputime/1.

trail_stack_allocated

  Unit : bytes

  Description : The amount of trail stack currently allocated. The trail is allocated in chunks, up to a maximum controlled by the -g command line option. The global stack and trail share the same memory area specified by the -g option, which thus gives the maximum possible combined allocated size of these two stacks.

trail_stack_peak

  Unit : bytes

  Description : The peak allocated size of the trail stack during this session. Chunks of memory can be allocated to, and deallocated from, the trail stack as it grows and shrinks.

trail_stack_used

  Unit : bytes

  Description : The amount of trail stack currently in use. The trail stack records information needed for backtracking and is subject to garbage collection.

wake_count

  Unit : count

  Description : The number of times suspensions (delayed goals) were woken up. This is an indicator for the activity of the constraints in a constraint program (but says nothing about whether this activity achieved any domain propagation or search space reduction).

NOTE: library(quintus) contains a compatibility version of statistics/2 which accepts the following different keywords: runtime, system_time, real_time, walltime, memory, program, global_stack, local_stack, trail, choice, stacks, garbage_collection, stack_shifts, atoms, atom_garbage_collection, core, heap.

### Modes and Determinism

- statistics(-, -) is multi
- statistics(+, -) is det

### Exceptions

(5) type error
  Keyword is neither an atom nor variable.

## Examples

    Success:
       [eclipse]: statistics(times, [_,_,T]).
       T = 2848.64
       yes.
       [eclipse]: statistics(global_stack_used, G).
       G = 136
       yes.
    Fail:
       statistics(times, [T]).
    Error:
       statistics("time", T).    (Error 5)

## See Also

set_flag / 2, env / 0, statistics / 0