The --axis <axis spec> option redefines the values in a benchmark's axis. It applies to the benchmark created by the most recent --benchmark argument, or all benchmarks if it precedes all --benchmark arguments (if any).

Valid axis specification follow the form:

• <axis_name>=<value>
• <axis_name>=[<value1>,<value2>,...]
• <axis_name>=[<start>:<stop>]
• <axis_name>=[<start>:<stop>:<stride>]
• <axis_name>[<flags>]=<value>
• <axis_name>[<flags>]=[<value1>,<value2>,...]
• <axis_name>[<flags>]=[<start>:<stop>]
• <axis_name>[<flags>]=[<start>:<stop>:<stride>]

Whitespace is ignored if the argument is quoted.

The axis type is taken from the benchmark definition. Some axes have additional restrictions:

• Numeric axes:
  • A single value, explicit list of values, or strided range may be specified.
  • For int64 axes, the power_of_two flag is specified by adding [pow2] after the axis name.
  • Values may differ from those defined in the benchmark.
• String axes:
  • A single value or explicit list of values may be specified.
  • Values may differ from those defined in the benchmark.
• Type axes:
  • A single value or explicit list of values may be specified.
  • Values MUST be a subset of the types defined in the benchmark.
  • Values MUST match the input strings provided by --list (e.g. I32 for int).
  • Provide a nvbench::type_strings<T> specialization to modify a custom type's input string.

Examples

Single Value

Axis Type	Example	Example Result
Int64	-a InputSize=12345	12345
Int64Pow2	-a InputSize[pow2]=8	256
Float64	-a Quality=0.5	0.5
String	-a RNG=Uniform	"Uniform"
Type	-a ValueType=I32	int32_t

Explicit List

Axis Type	Example	Example Result
Int64	-a InputSize=[1,2,3,4,5]	1, 2, 3, 4, 5
Int64Pow2	-a InputSize[pow2]=[4,6,8,10]	16, 64, 256, 1024
Float64	-a Quality=[0.5,0.75,1.0]	0.5, 0.75, 1.0
String	-a RNG=[Uniform,Gaussian]	"Uniform", "Gaussian"
Type	-a ValueType=[U8,I32,F64]	uint8_t, int32_t, double

Strided Range

Axis Type	Example	Example Result
Int64	-a InputSize=[2:10:2]	2, 4, 6, 8, 10
Int64Pow2	-a InputSize[pow2]=[2:10:2]	4, 16, 64, 256, 1024
Float64	-a Quality=[.5:1:.1]	0.5, 0.6, 0.7, 0.8, 0.9, 1.0
String	[Not supported]
Type	[Not supported]