Expression Language¶

PHPBench has a general purpose expression language which is used when writing assertions.

Comparators ¶

comparator	description
<	Less than
<=	Less than or equal
=	Equal
>	Greater than
>=	Greater than or equal

Examples:

10 microseconds < 20 microseconds

Logical Operators ¶

comparator	description
and	Logical and
or	Logical or

Examples:

1 < 2 and 3 < 4
(1 < 2 and 3 < 4) or true

String Operators ¶

comparator	description
`~`	Concatenate

Examples:

"mode: " ~ mode([12, 12, 12]) ~ " \o/"

Arithmetic ¶

comparator	description
`+`	Addition
`-`	Subtraction
`/`	Divide
`*`	Multiply

Examples:

+ 1 = 2
+ 3 * 4 + 5 = 19
+ (3 * 4) + 5 = 19
(2 + 3) * 4 + 5 = 25

Time Units ¶

The base unit for time in PHPBench is microseconds. By specifying a timeunit you can represent other units - internally the unit will be converted to microseconds:

unit	description
microsecond	1,000,000th of a second
millisecond	1,000th of a second
second	1 second
minute	60 seconds
hour	3,600 seconds
day	86,400 seconds
time	Automatic

Examples:

milliseconds
seconds < 20 days
days = (3600 seconds * 24) * 360

Memory Units:¶

unit	description
byte	1 byte
kilobyte	1,000 bytes
megabyte	1,000,000 bytes
gigabyte	1,000,000,000 bytes
memory	Automatic

For example:

1 megabytes < 2 megabytes
1 bytes + 2 megabytes

Display As ¶

Parameterized values (e.g. variant.time.avg) are always provided the base unit. You can use as to display these values in a specified unit:

1000000 as seconds = 1 second

This will force the unit conversion to happen only when displaying the evaluated expression.

You can also specify the precision:

1000000 as seconds precision 4 = 1 second

Will ensure that the result is displayed with the given number of digits after the decimal point.

Tolerance ¶

In practice two runs will rarely return exactly the same result. To allow a tolerable variance you can specify a tolerance as follows:

9 milliseconds <= 10 milliseconds +/- 10%

With the above values within 8 to 12 milliseconds will be tolerated.

You can also specify a percentage value:

9 milliseconds <= 10 milliseconds +/- 2 milliseconds

Functions ¶

max ¶

Return the max value in a set of values:

max([10, 12, 4, 20]) = 20

mean ¶

Return the mean (i.e. average) value in a set of values:

mean([1, 2, 1, 2]) = 1.5

min ¶

Return the min value in a set of values:

min([10, 12, 4, 20]) = 4

mode ¶

Return the KDE mode value in a set of values:

mode([1, 2, 1, 2]) = 1.5 +/- 0.00000000001

In PHPBench the mode is generally the best predictor.

percent_diff ¶

Return the percentage difference between two values

percent_diff(1, 2) = 100

stdev ¶

Return the standard deviation for a set of values:

stdev([1,2]) = 0.5

rstdev ¶

Return the relative standard deviation for a set of values:

rstdev([1,2]) = 33.3333 +/- 0.0001
rstdev([1,2], true) = 47.1405 +/- 0.0001
format("%2.4f%%", rstdev([1,2])) = "33.3333%"

variance ¶

Return the variance for a set of values:

variance([1,2]) = 0.25

format ¶

Format values as a string - uses sprintf:

format("hello %s", "daniel") = "hello daniel"
format("%2.4f%%", rstdev([1,2])) = "33.3333%"

join ¶

Join values with a delimiter

join(",", ["one", "two"]) = "one,two"

first ¶

Return the first element in an array, or throw an evaluation error.

first(["one", "two"]) = "one"

coalesce ¶

Return the first non-null element from the given arguments:

coalesce(null, null, 10) = 10

display_as_time ¶

Similar to Display As but also allows specification of the “mode”

display_as_time(100000, "seconds", 2, "throughput") = 100000