System statistics

7.24 System statistics

7.24.1 `statistics/0`, `statistics/2`

Templates

: statistics statistics(?atom, ?list)

Description

statistics displays statistics about memory usage and run times.

statistics(Key, Value) unifies Value with the current value of the statistics key Key. Value a list of two elements. Times are in milliseconds, sizes of areas in bytes.

Key	Description	Value
`user_time`	user CPU time	`[SinceStart, SinceLast]`
`system_time`	system CPU time	`[SinceStart, SinceLast]`
`cpu_time`	total CPU time (user + system)	`[SinceStart, SinceLast]`
`real_time`	absolute time	`[SinceStart, SinceLast]`
`local_stack`	local stack sizes (control, environments, choices)	`[UsedSize, FreeSize]`
`global_stack`	global stack sizes (compound terms)	`[UsedSize, FreeSize]`
`trail_stack`	trail stack sizes (variable bindings to undo)	`[UsedSize, FreeSize]`
`cstr_stack`	constraint trail sizes (finite domain constraints)	`[UsedSize, FreeSize]`

Note that the key runtime is recognized as user_time for compatibility purpose.

Errors


`Key` is neither a variable nor a valid key		`domain_error(statistics_key, Key)`

`Value` is neither a variable nor a list of two elements		`domain_error(statistics_value, Value)`

`Value` is a list of two elements and an element `E` is neither a variable nor an integer		`type_error(integer, E)`

Portability

GNU Prolog predicates.

7.24.2 `user_time/1`, `system_time/1`, `cpu_time/1`, `real_time/1`

Templates

: user_time(?integer) system_time(?integer) cpu_time(?integer) real_time(?integer)

Description

user_time(Time) unifies Time with the user CPU time elapsed since the start of Prolog.

system_time(Time) unifies Time with the system CPU time elapsed since the start of Prolog.

cpu_time(Time) unifies Time with the CPU time (user + system) elapsed since the start of Prolog.

real_time(Time) unifies Time with the absolute time elapsed since the start of Prolog.