loki.transformations.transform_loop

Collection of utility routines that provide loop transformations.

Functions

do_loop_fission(routine[, promote, ...])	Search for !$loki loop-fission pragmas in loops and split them.
do_loop_fusion(routine)	Search for loops annotated with the loki loop-fusion pragma and attempt to fuse them into a single loop.
do_loop_interchange(routine[, project_bounds])	Search for loops annotated with the loki loop-interchange pragma and attempt to reorder them.
do_loop_unroll(routine[, warn_iterations_length])	Search for !$loki loop-unroll pragmas in loops and unroll them.
eliminate_variable(polyhedron, index_or_variable)	Eliminate a variable from the polyhedron.
generate_loop_bounds(iteration_space, ...)	Generate loop bounds according to a changed iteration order.
get_loop_components(loops)	Helper routine to extract loop variables, ranges and bodies of list of loops.
get_nested_loops(loop, depth)	Helper routine to extract all loops in a loop nest.
pragma_ranges_to_loop_ranges(parameters, scope)	Convert loop ranges given in the pragma parameters from string to a tuple of LoopRange objects.

Classes

FissionTransformer(loop_pragmas[, active])	Bespoke transformer that splits loops or loop nests at !$loki loop-fission pragmas.
LoopUnrollTransformer([warn_iterations_length])	Transformer that unrolls loops or loop nests at !$loki loop-unroll pragmas.
TransformLoopsTransformation([...])	A Transformation that provides a common location for the various loop transformations to be called in a Scheduler pipeline.

do_loop_interchange(routine, project_bounds=False)

Search for loops annotated with the loki loop-interchange pragma and attempt to reorder them.

Note that this effectively just exchanges variable and bounds for each of the loops, leaving the rest (including bodies, pragmas, etc.) intact.

do_loop_fusion(routine)

Search for loops annotated with the loki loop-fusion pragma and attempt to fuse them into a single loop.

do_loop_fission(routine, promote=True, warn_loop_carries=True)

Search for !$loki loop-fission pragmas in loops and split them.

The expected pragma syntax is !$loki loop-fission [collapse(n)] [promote(var-name, var-name, ...)] where collapse(n) gives the loop nest depth to be split (defaults to n=1) and promote optionally specifies a list of variable names to be promoted by the split iteration space dimensions.

Parameters:

• routine (Subroutine) – The subroutine in which loop fission is to be applied.

• promote (bool, optional) – Try to automatically detect read-after-write across fission points and promote corresponding variables. Note that this does not affect promotion of variables listed directly in the pragma’s promote option.

• warn_loop_carries (bool, optional) – Try to automatically detect loop-carried dependencies and warn when the fission point sits after the initial read and before the final write.

do_loop_unroll(routine, warn_iterations_length=True)

Search for !$loki loop-unroll pragmas in loops and unroll them.

The expected pragma syntax is !$loki loop-unroll [depth(n)] where depth(n) controls the unrolling of nested loops. For instance, depth(1) will only unroll the top most loop of a set of nested loops. However, a child nested loop with a more restrictive depth will not be able to override its parent’s depth. If depth(n) is not specified, then all loops nested under a parent with this pragma will be unrolled. E.g. The code sample below will only unroll A and B, but not C:

! Loop A !$loki loop-unroll depth(1) DO a = 1, 10

! Loop B !$loki loop-unroll DO b = 1, 10

…

END DO ! Loop C - will not be unrolled DO c = 1, 10

…

END DO

END DO

Parameters:

• routine (Subroutine) – The subroutine in which loop unrolling is to be applied.

• warn_iterations_length ('Boolean', optional) – This specifies if warnings should be generated when unrolling loops with a large number of iterations (32). It’s mainly to disable warnings when loops are being unrolled for internal transformations and analysis.

class TransformLoopsTransformation(loop_interchange=False, loop_fusion=False, loop_fission=False, loop_unroll=False, interchange_project_bounds=False, fission_promote=True, fission_warn_loop_carries=True, unroll_warn_iterations_length=True)

Bases: Transformation

A Transformation that provides a common location for the various loop transformations to be called in a Scheduler pipeline.

The transformation applies the following methods in order:

• do_loop_interchange

• do_loop_fusion

• do_loop_fission

• do_loop_unroll

Parameters:

• loop_interchange (bool) – Run the do_loop_interchange utility. Default: False.

• loop_fusion (bool) – Run the do_loop_fusion utility. Default: False.

• loop_fission (bool) – Run the do_loop_fission utility. Default: False.

• loop_unroll (bool) – Run the do_loop_unroll utility. Default: False.

• interchange_project_bounds (bool) – Project loop bounds whilst performing loop interchange. Default: False.

• fission_promote (bool) – Try to automatically detect read-after-write across fission points and promote corresponding variables. Note that this does not affect promotion of variables listed directly in the pragma’s promote option. Default: True.

• fission_warn_loop_carries (bool) – Try to automatically detect loop-carried dependencies and warn when the fission point sits after the initial read and before the final write. Default: True.

• unroll_warn_iterations_length (bool) – This specifies if warnings should be generated when unrolling loops with a large number of iterations (32). It’s mainly to disable warnings when loops are being unrolled for internal transformations and analysis. Default: True.

transform_subroutine(routine, **kwargs)

Defines the transformation to apply to Subroutine items.

For transformations that modify Subroutine objects, this method should be implemented. It gets called via the dispatch method apply().

Parameters:

• routine (Subroutine) – The subroutine to be transformed.

• **kwargs (optional) – Keyword arguments for the transformation.