Prolog system internal predicates

(Trust) Usage:

Prints statistics about the system.

Usage 1:statistics(Tick_option,Tick_result)

Gather information about clock ticks (either run, user, system or wall tick) since last consult or since start of program. A tick is the smallest amount of time that a clock can measure.

• The following properties should hold at call time:
  (prolog_sys:tick_option/1)Options to get information about execution ticks.
  (basic_props:term/1)Tick_result is any term.
• The following properties should hold upon exit:
  (prolog_sys:tick_option/1)Options to get information about execution ticks.
  (prolog_sys:tick_result/1)Tick_result is a two-element list of numbers. The first number is the number of ticks since the start of the execution; the second number is the number of ticks since the previous consult to tick.

Usage 2:statistics(Clockfreq_option,Clockfreq_result)

Gather information about frequency of the clocks used to measure the ticks (either run-user, system or wall clock). Results are returned in hertz. This value also can be defined as the amount of ticks that a clock can measure in one second.

• The following properties should hold at call time:
  (prolog_sys:clockfreq_option/1)Options to get information about the frequency of clocks used to get the ticks.
  (basic_props:term/1)Clockfreq_result is any term.
• The following properties should hold upon exit:
  (prolog_sys:clockfreq_option/1)Options to get information about the frequency of clocks used to get the ticks.
  (prolog_sys:clockfreq_result/1)Clockfreq_result is a number. It gives the frequency in hertz used by the clock get the ticks.

Usage 3:statistics(Time_option,Time_result)

Gather information about time (either process time or wall time) since last consult or since start of program. Results are returned in milliseconds. Note that internally, time is calculated as:

  Time_result = (Tick_result / Clockfreq_result) * 1000

• The following properties should hold at call time:
  (prolog_sys:time_option/1)Options to get information about execution time. Time_option must be one of runtime, usertime, systemtime or walltime.
  (basic_props:term/1)Time_result is any term.
• The following properties should hold upon exit:
  (prolog_sys:time_option/1)Options to get information about execution time. Time_option must be one of runtime, usertime, systemtime or walltime.
  (prolog_sys:time_result/1)Time_result is a two-element list of numbers. The first number is the time since the start of the execution; the second number is the time since the previous consult to time.

Usage 4:statistics(Memory_option,Memory_result)

Gather information about memory consumption.

• The following properties should hold at call time:
  (prolog_sys:memory_option/1)Options to get information about memory usage.
  (basic_props:term/1)Memory_result is any term.
• The following properties should hold upon exit:
  (prolog_sys:memory_option/1)Options to get information about memory usage.
  (prolog_sys:memory_result/1)Result is a two-element list of integers. The first element is the space taken up by the option selected, measured in bytes; the second integer is zero for program space (which grows as necessary), and the amount of free space otherwise.

Usage 5:statistics(Garbage_collection_option,Gc_result)

Gather information about garbage collection.

• The following properties should hold at call time:
  (prolog_sys:garbage_collection_option/1)Options to get information about garbage collection.
  (basic_props:term/1)Gc_result is any term.
• The following properties should hold upon exit:
  (prolog_sys:garbage_collection_option/1)Options to get information about garbage collection.
  (prolog_sys:gc_result/1)Gc_result is a tree-element list of integers, related to garbage collection and memory management. When stack_shifts is selected, the first one is the number of shifts (reallocations) of the local stack; the second is the number of shifts of the trail, and the third is the time spent in these shifts. When garbage_collection is selected, the numbers are, respectively, the number of garbage collections performed, the number of bytes freed, and the time spent in garbage collection.

Usage 6:statistics(Symbol_option,Symbol_result)

Gather information about number of symbols and predicates.

• The following properties should hold at call time:
  (prolog_sys:symbol_option/1)Option to get information about the number of symbols in the program.
  (basic_props:term/1)Symbol_result is any term.
• The following properties should hold upon exit:
  (prolog_sys:symbol_option/1)Option to get information about the number of symbols in the program.
  (prolog_sys:symbol_result/1)Symbol_result is a two-element list of integers. The first one is the number of atom, functor, and predicate names in the symbol table. The second is the number of predicates known to be defined (although maybe without clauses).

Usage 7:statistics(Option,Arg2)

If Option is unbound, it is bound to the values on the other cases.

• Call and exit should be compatible with:
  (basic_props:term/1)Arg2 is any term.
• The following properties should hold upon exit:
  (basic_props:term/1)Arg2 is any term.

(True) Usage:clockfreq_result(Result)

Result is a number. It gives the frequency in hertz used by the clock get the ticks.

(True) Usage:tick_result(Result)

Result is a two-element list of numbers. The first number is the number of ticks since the start of the execution; the second number is the number of ticks since the previous consult to tick.

(Trust) Usage:new_atom(Atom)

Returns, on success, a new atom, not existing before in the system. The entry argument must be a variable. The idea behind this atom generation is to provide a fast source of identifiers for new objects, concurrent predicates, etc. on the fly.

• The following properties should hold at call time:
  (term_typing:var/1)Atom is a free variable.
• The following properties hold upon exit:
  (basic_props:atm/1)Atom is an atom.

(True) Usage:symbol_result(Result)

Result is a two-element list of integers. The first one is the number of atom, functor, and predicate names in the symbol table. The second is the number of predicates known to be defined (although maybe without clauses).

(True) Usage:gc_result(Result)

Result is a tree-element list of integers, related to garbage collection and memory management. When stack_shifts is selected, the first one is the number of shifts (reallocations) of the local stack; the second is the number of shifts of the trail, and the third is the time spent in these shifts. When garbage_collection is selected, the numbers are, respectively, the number of garbage collections performed, the number of bytes freed, and the time spent in garbage collection.

(True) Usage:memory_result(Result)

Result is a two-element list of integers. The first element is the space taken up by the option selected, measured in bytes; the second integer is zero for program space (which grows as necessary), and the amount of free space otherwise.

(True) Usage:time_result(Result)

Result is a two-element list of numbers. The first number is the time since the start of the execution; the second number is the time since the previous consult to time.

(True) Usage:symbol_option(M)

Option to get information about the number of symbols in the program.

(True) Usage:garbage_collection_option(M)

Options to get information about garbage collection.

(True) Usage:memory_option(M)

Options to get information about memory usage.

(True) Usage:clockfreq_option(M)

Options to get information about the frequency of clocks used to get the ticks.

(True) Usage:tick_option(M)

Options to get information about execution ticks.

(True) Usage:time_option(M)

Options to get information about execution time. M must be one of runtime, usertime, systemtime or walltime.

Usage:predicate_property(Head,Property)

The predicate Head, visible from the current module, (a goal) has the property Property.

• The following properties should hold upon exit:
  (basic_props:callable/1)Head is a term which represents a goal, i.e., an atom or a structure.
  (basic_props:atm/1)Property is an atom.

Test:predicate_property(Head,Prop)

Predicate property of true/0 is compiled

• If the following properties hold at call time:
  (term_basic:= /2)term_basic:Head=true
  then the following properties should hold upon exit:
  (term_basic:= /2)term_basic:Prop=compiled

(Trust) Usage:current_atom(Atom)

Enumerates on backtracking all the existing atoms in the system.

• The following properties hold upon exit:
  (basic_props:atm/1)Atom is an atom.

(Trust) Usage:

Forces garbage collection when called.