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# Author: R. W. Ford, STFC Daresbury Lab
'''Module providing a transformation from a PSyIR MINVAL intrinsic to
an equivalent PSyIR loop structure. This could be useful if the MINVAL
operator is not supported by the back-end, the required
parallelisation approach, or if the performance in the inline code is
better than the intrinsic.
'''
from psyclone.psyir.nodes import IntrinsicCall
from psyclone.psyir.transformations.intrinsics.array_reduction_base_trans \
import ArrayReductionBaseTrans
[docs]class Minval2LoopTrans(ArrayReductionBaseTrans):
'''Provides a transformation from a PSyIR MINVAL IntrinsicCall node to
an equivalent PSyIR loop structure that is suitable for running in
parallel on CPUs and GPUs. Validity checks are also performed.
If MINVAL contains a single positional argument which is an array,
the minimum value of all of the elements in the array is returned
in the the scalar R.
.. code-block:: fortran
R = MINVAL(ARRAY)
For example, if the array is two dimensional, the equivalent code
for real data is:
.. code-block:: fortran
R = HUGE(R)
DO J=LBOUND(ARRAY,2),UBOUND(ARRAY,2)
DO I=LBOUND(ARRAY,1),UBOUND(ARRAY,1)
R = MIN(R, ARRAY(I,J))
If the mask argument is provided then the mask is used to
determine whether the minval is applied:
.. code-block:: fortran
R = MINVAL(ARRAY, mask=MOD(ARRAY, 2.0)==1)
If the array is two dimensional, the equivalent code
for real data is:
.. code-block:: fortran
R = HUGE(R)
DO J=LBOUND(ARRAY,2),UBOUND(ARRAY,2)
DO I=LBOUND(ARRAY,1),UBOUND(ARRAY,1)
IF (MOD(ARRAY(I,J), 2.0)==1) THEN
R = MIN(R, ARRAY(I,J))
The dimension argument is currently not supported and will result
in a TransformationError exception being raised.
.. code-block:: fortran
R = MINVAL(ARRAY, dimension=2)
The array passed to MINVAL may use any combination of array
syntax, array notation, array sections and scalar bounds:
.. code-block:: fortran
R = MINVAL(ARRAY) ! array syntax
R = MINVAL(ARRAY(:,:)) ! array notation
R = MINVAL(ARRAY(1:10,lo:hi)) ! array sections
R = MINVAL(ARRAY(1:10,:)) ! mix of array section and array notation
R = MINVAL(ARRAY(1:10,2)) ! mix of array section and scalar bound
For example:
>>> from psyclone.psyir.backend.fortran import FortranWriter
>>> from psyclone.psyir.frontend.fortran import FortranReader
>>> from psyclone.psyir.transformations import Minval2LoopTrans
>>> code = ("subroutine minval_test(array)\\n"
... " real :: array(10,10)\\n"
... " real :: result\\n"
... " result = minval(array)\\n"
... "end subroutine\\n")
>>> psyir = FortranReader().psyir_from_source(code)
>>> sum_node = psyir.children[0].children[0].children[1]
>>> Minval2LoopTrans().apply(sum_node)
>>> print(FortranWriter()(psyir))
subroutine minval_test(array)
real, dimension(10,10) :: array
real :: result
integer :: idx
integer :: idx_1
<BLANKLINE>
result = HUGE(result)
do idx = 1, 10, 1
do idx_1 = 1, 10, 1
result = MIN(result, array(idx_1,idx))
enddo
enddo
<BLANKLINE>
end subroutine minval_test
<BLANKLINE>
'''
_INTRINSIC_NAME = "MINVAL"
_INTRINSIC_TYPE = IntrinsicCall.Intrinsic.MINVAL
def _loop_body(self, lhs, rhs):
'''Provide the body of the nested loop that computes the minimum value
of the lhs and rhs.
:param lhs: the lhs value for the min operation.
:type lhs: :py:class:`psyclone.psyir.nodes.Node`
:param rhs: the rhs value for the min operation.
:type rhs: :py:class:`psyclone.psyir.nodes.Node`
:returns: a MIN IntrinsicCall.
:rtype: :py:class:`psyclone.psyir.nodes.IntrinsicCall`
'''
# return min(lhs,rhs)
return IntrinsicCall.create(IntrinsicCall.Intrinsic.MIN, [lhs, rhs])
def _init_var(self, reference):
'''The initial value for the variable that computes the minimum value
of an array.
:param reference: the reference used to store the final result.
:type reference: :py:class:`psyclone.psyir.node.Reference`
:returns: PSyIR for the value to initialise the variable that
computes the minimum value.
:rtype: :py:class:`psyclone.psyir.nodes.IntrinsicCall`
'''
return IntrinsicCall.create(
IntrinsicCall.Intrinsic.HUGE, [reference.copy()])