Halide::LoopLevel Class Reference

A reference to a site in a Halide statement at the top of the body of a particular for loop. More...

#include <Schedule.h>

Public Member Functions
int	stage_index () const
	Return the index of the function stage associated with this loop level. More...
	LoopLevel (const Internal::Function &f, const VarOrRVar &v, int stage_index=-1)
	Identify the loop nest corresponding to some dimension of some function. More...
	LoopLevel (const Func &f, const VarOrRVar &v, int stage_index=-1)
	LoopLevel ()
	Construct an undefined LoopLevel. More...
void	set (const LoopLevel &other)
	Mutate our contents to match the contents of 'other'. More...
LoopLevel &	lock ()
std::string	func () const
VarOrRVar	var () const
bool	defined () const
bool	is_inlined () const
bool	is_root () const
std::string	to_string () const
bool	match (const std::string &loop) const
bool	match (const LoopLevel &other) const
bool	operator== (const LoopLevel &other) const
bool	operator!= (const LoopLevel &other) const

Static Public Member Functions
static LoopLevel	inlined ()
	Construct a special LoopLevel value that implies that a function should be inlined away. More...
static LoopLevel	root ()
	Construct a special LoopLevel value which represents the location outside of all for loops. More...

Detailed Description

A reference to a site in a Halide statement at the top of the body of a particular for loop.

Evaluating a region of a halide function is done by generating a loop nest that spans its dimensions. We schedule the inputs to that function by recursively injecting realizations for them at particular sites in this loop nest. A LoopLevel identifies such a site. The site can either be a loop nest within all stages of a function or it can refer to a loop nest within a particular function's stage (initial definition or updates).

Note that a LoopLevel is essentially a pointer to an underlying value; all copies of a LoopLevel refer to the same site, so mutating one copy (via the set() method) will effectively mutate all copies:

Func f;
Var x;
LoopLevel a(f, x);
// Both a and b refer to LoopLevel(f, x)
LoopLevel b = a;
// Now both a and b refer to LoopLevel::root()
a.set(LoopLevel::root());

This is quite useful when splitting Halide code into utility libraries, as it allows a library to schedule code according to a caller's specifications, even if the caller hasn't fully defined its pipeline yet:

Func demosaic(Func input,
             LoopLevel intermed_compute_at,
             LoopLevel intermed_store_at,
             LoopLevel output_compute_at) {
   Func intermed = ...;
   Func output = ...;
   intermed.compute_at(intermed_compute_at).store_at(intermed_store_at);
   output.compute_at(output_compute_at);
   return output;
}
 
void process() {
    // Note that these LoopLevels are all undefined when we pass them to demosaic()
    LoopLevel intermed_compute_at, intermed_store_at, output_compute_at;
    Func input = ...;
    Func demosaiced = demosaic(input, intermed_compute_at, intermed_store_at, output_compute_at);
    Func output = ...;
 
    // We need to ensure all LoopLevels have a well-defined value prior to lowering:
    intermed_compute_at.set(LoopLevel(output, y));
    intermed_store_at.set(LoopLevel(output, y));
    output_compute_at.set(LoopLevel(output, x));
}

Definition at line 176 of file Schedule.h.

Constructor & Destructor Documentation

LoopLevel() [1/3]

Halide::LoopLevel::LoopLevel	(	const Internal::Function &	f,
		const VarOrRVar &	v,
		int	stage_index = -1
	)

Identify the loop nest corresponding to some dimension of some function.

LoopLevel() [2/3]

Halide::LoopLevel::LoopLevel	(	const Func &	f,
		const VarOrRVar &	v,
		int	stage_index = -1
	)

LoopLevel() [3/3]

Halide::LoopLevel::LoopLevel

(

)

Construct an undefined LoopLevel.

Calling any method on an undefined LoopLevel (other than set()) will assert.

Member Function Documentation

stage_index()

int Halide::LoopLevel::stage_index

(

)

const

Return the index of the function stage associated with this loop level.

Asserts if undefined

inlined()

static LoopLevel Halide::LoopLevel::inlined ( )

static

Construct a special LoopLevel value that implies that a function should be inlined away.

Referenced by Halide::Internal::GeneratorParam_LoopLevel::set_from_string().

root()

static LoopLevel Halide::LoopLevel::root ( )

static

Construct a special LoopLevel value which represents the location outside of all for loops.

Referenced by Halide::Internal::GeneratorParam_LoopLevel::set_from_string().

set()

void Halide::LoopLevel::set

(

const LoopLevel &

other

)

Mutate our contents to match the contents of 'other'.

Referenced by Halide::Internal::GeneratorParam_LoopLevel::get_default_value(), and Halide::Internal::GeneratorParam_LoopLevel::set().

lock()

LoopLevel& Halide::LoopLevel::lock

(

)

Referenced by Halide::Internal::GeneratorParam_LoopLevel::get_default_value().

func()

std::string Halide::LoopLevel::func

(

)

const

var()

VarOrRVar Halide::LoopLevel::var

(

)

const

defined()

bool Halide::LoopLevel::defined

(

)

const

is_inlined()

bool Halide::LoopLevel::is_inlined

(

)

const

Referenced by Halide::Internal::GeneratorParam_LoopLevel::get_default_value().

is_root()

bool Halide::LoopLevel::is_root

(

)

const

Referenced by Halide::Internal::GeneratorParam_LoopLevel::get_default_value().

to_string()

std::string Halide::LoopLevel::to_string

(

)

const

match() [1/2]

bool Halide::LoopLevel::match

(

const std::string &

loop

)

const

match() [2/2]

bool Halide::LoopLevel::match

(

const LoopLevel &

other

)

const

operator==()

bool Halide::LoopLevel::operator==

(

const LoopLevel &

other

)

const

operator!=()

bool Halide::LoopLevel::operator!= ( const LoopLevel &  other ) const

inline

Definition at line 250 of file Schedule.h.

---

The documentation for this class was generated from the following file:

• src/Schedule.h