sdfg::transformations::LoopSkewing Class Reference

Loop skewing transformation for nested loops. More...

#include <sdfg/transformations/loop_skewing.h>

Inheritance diagram for sdfg::transformations::LoopSkewing:

Public Member Functions
	LoopSkewing (structured_control_flow::StructuredLoop &outer_loop, structured_control_flow::StructuredLoop &inner_loop, int skew_factor=1)
	Construct a new Loop Skewing transformation.
virtual std::string	name () const override
	Get the name of this transformation.
virtual bool	can_be_applied (builder::StructuredSDFGBuilder &builder, analysis::AnalysisManager &analysis_manager) override
	Check if this transformation can be safely applied.
virtual void	apply (builder::StructuredSDFGBuilder &builder, analysis::AnalysisManager &analysis_manager) override
	Apply this transformation to the SDFG.
virtual void	to_json (nlohmann::json &j) const override
	Serialize this transformation to JSON.
Public Member Functions inherited from sdfg::transformations::Transformation
virtual	~Transformation ()=default
virtual void	set_report (PassReportConsumer *report)
	Set the report consumer for transformation feedback.
virtual bool	try_apply (builder::StructuredSDFGBuilder &builder, analysis::AnalysisManager &analysis_manager)
	Attempt to apply the transformation if possible.

Static Public Member Functions
static LoopSkewing	from_json (builder::StructuredSDFGBuilder &builder, const nlohmann::json &j)

Additional Inherited Members
Protected Attributes inherited from sdfg::transformations::Transformation
PassReportConsumer *	report_ = nullptr

Detailed Description

Loop skewing transformation for nested loops.

This transformation applies loop skewing to two nested loops by adjusting the inner loop's iteration space to depend on the outer loop's iteration variable.

Loop skewing is useful for:

• Exposing parallelism in loops with loop-carried dependencies
• Improving cache locality by changing the iteration order
• Enabling other transformations like wavefront parallelization

Transformation: for (i = lb_i; i < ub_i; i++) for (j = lb_j; j < ub_j; j++) body[i][j]

Becomes: for (i' = lb_i; i' < ub_i; i'++) for (j' = lb_j + skew_factor * (i' - lb_i); j' < ub_j + skew_factor * (i' - lb_i); j'++) body[i'][j' - skew_factor * (i' - lb_i)]

Implementation:

• Uses builder.update_loop() to modify the inner loop in place
• Uses root().replace() to update memory access patterns
• No new loops are created, transformation modifies existing loop

Prerequisites:

• Two properly nested loops (outer loop contains only inner loop)
• Both loops can be any StructuredLoop (For or Map)
• Inner loop update must not depend on the outer loop iteration variable
• Non-zero skew factor

Constructor & Destructor Documentation

LoopSkewing()

sdfg::transformations::LoopSkewing::LoopSkewing	(	structured_control_flow::StructuredLoop &	outer_loop,
		structured_control_flow::StructuredLoop &	inner_loop,
		int	skew_factor = 1 )

Construct a new Loop Skewing transformation.

Parameters

outer_loop	The outer loop to skew
inner_loop	The inner loop to skew
skew_factor	The skewing factor (default: 1)

Member Function Documentation

apply()

virtual void sdfg::transformations::LoopSkewing::apply ( builder::StructuredSDFGBuilder & builder, analysis::AnalysisManager & analysis_manager )

overridevirtual

Apply this transformation to the SDFG.

Parameters

builder	The SDFG builder
analysis_manager	The analysis manager (may be invalidated)

Implements sdfg::transformations::Transformation.

can_be_applied()

virtual bool sdfg::transformations::LoopSkewing::can_be_applied ( builder::StructuredSDFGBuilder & builder, analysis::AnalysisManager & analysis_manager )

overridevirtual

Check if this transformation can be safely applied.

Parameters

builder	The SDFG builder
analysis_manager	The analysis manager providing necessary analyses

Returns

true if all preconditions are met

Implements sdfg::transformations::Transformation.

from_json()

LoopSkewing sdfg::transformations::LoopSkewing::from_json ( builder::StructuredSDFGBuilder & builder, const nlohmann::json & j )

static

name()

virtual std::string sdfg::transformations::LoopSkewing::name ( ) const

overridevirtual

Get the name of this transformation.

Returns

The transformation name (e.g., "LoopInterchange")

Implements sdfg::transformations::Transformation.

to_json()

virtual void sdfg::transformations::LoopSkewing::to_json ( nlohmann::json & j ) const

overridevirtual

Serialize this transformation to JSON.

Parameters

j	JSON object to populate with transformation description

Exceptions

std::logic_error

if not implemented

Implements sdfg::transformations::Transformation.

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

• opt/include/sdfg/transformations/loop_skewing.h