Manual Reference Pages - reshape (3fortran)
reshape
NAME
RESHAPE(3) - [ARRAY:RESHAPE] Function to reshape an array
SYNOPSIS
result = reshape( source, shape [,pad] [,order] )
type(TYPE(kind=KIND)) function reshapetype(TYPE(kind=KIND)),intent(in) :: source(..) integer(kind=**),intent(in) :: shape(:) type(TYPE(kind=KIND)),intent(in),optional :: pad(..) integer(kind=**),intent(in),optional :: order(:)
CHARACTERISTICS
o SOURCE is an array of any type o SHAPE defines a Fortran shape and therefore an integer vector (of rank one) of constant size of up to 16 non-negative values. o PAD is the same type as SOURCE o ORDER is the same shape as SHAPE o The result is an array of shape SHAPE with the same type as SOURCE. o a kind designated as ** may be any supported kind for the type
DESCRIPTION
RESHAPE constructs an array of arbitrary shape SHAPE using the elements from SOURCE and possibly PAD to fill it.
If necessary, the new array may be padded with elements from PAD or permuted as defined by ORDER.
Among many other uses, RESHAPE can be used to reorder a Fortran array to match C array ordering before the array is passed from Fortran to a C procedure.
OPTIONS
o SOURCE : an array containing the elements to be copied to the result. there must be enough elements in the source to fill the new shape if PAD is omitted or has size zero. Expressed in Fortran ... if(.not.present(pad))then if(size(source) < product(shape))then stop ’not enough elements in the old array to fill the new one’ endif endif
o SHAPE : This is the shape of the new array being generated. Being by definition a shape; all elements are either positive integers or zero, the size but be 1 or greater, it may have up to 16 elements but must be of constant fixed size and rank one. o PAD : used to fill in extra values if the result array is larger than SOURCE. It will be used repeatedly after all the elements of SOURCE have been placed in the result until the result has all elements assigned. : If it is absent or is a zero-sized array, you can only make SOURCE into another array of the same size as SOURCE or smaller. o ORDER : used to insert elements in the result in an order other than the normal Fortran array element order, in which the first dimension varies fastest. : By definition of ranks the values have to be a permutation of the numbers from 1 to n, where n is the rank of SHAPE. : the elements of SOURCE and pad are placed into the result in order; changing the left-most rank most rapidly by default. To change the order by which the elements are placed in the result use ORDER.
RESULT
The result is an array of shape SHAPE with the same type and type parameters as SOURCE. It is first filled with the values of elements of SOURCE, with the remainder filled with repeated copies of PAD until all elements are filled. The new array may be smaller than SOURCE.
EXAMPLES
Sample program:
program demo_reshape implicit none ! notice the use of "shape(box)" on the RHS integer :: box(3,4)=reshape([1,2,3,4,5,6,7,8,9,10,11,12],shape(box)) integer,allocatable :: v(:,:) integer :: rc(2) ! basics0 ! what is the current shape of the array? call printi(’shape of box is ’,box) ! change the shape call printi(’reshaped ’,reshape(box,[2,6])) call printi(’reshaped ’,reshape(box,[4,3]))Results:! fill in row column order using order v=reshape([1,2,3,4,10,20,30,40,100,200,300,400],[1,12]) call printi(’here is some data to shape’,v) call printi(’normally fills columns first ’,reshape([v],[3,4])) call printi(’fill rows first’, reshape([v],[3,4],order=[2,1]))
! if we take the data and put in back in filling ! rows first instead of columns, and flipping the ! height and width of the box we not only fill in ! a vector using row-column order we actually ! transpose it. rc(2:1:-1)=shape(box) ! copy the data in changing column number fastest v=reshape(box,rc,order=[2,1]) call printi(’reshaped and reordered’,v) ! of course we could have just done a transpose call printi(’transposed’,transpose(box))
! making the result bigger than source using pad v=reshape(box,rc*2,pad=[-1,-2,-3],order=[2,1]) call printi(’bigger and padded and reordered’,v) contains
subroutine printi(title,arr) implicit none
!@(#) print small 2d integer arrays in row-column format
character(len=*),parameter :: all=’(*(g0,1x))’ ! a handy format character(len=*),intent(in) :: title integer,intent(in) :: arr(:,:) integer :: i character(len=:),allocatable :: biggest
print all print all, trim(title),’:(’,shape(arr),’)’ ! print title biggest=’ ’ ! make buffer to write integer into ! find how many characters to use for integers write(biggest,’(i0)’)ceiling(log10(max(1.0,real(maxval(abs(arr))))))+2 ! use this format to write a row biggest=’(" > [",*(i’//trim(biggest)//’:,","))’ ! print one row of array at a time do i=1,size(arr,dim=1) write(*,fmt=biggest,advance=’no’)arr(i,:) write(*,’(" ]")’) enddo
end subroutine printi
end program demo_reshape
shape of box is :( 3 4 ) > [ 1, 4, 7, 10 ] > [ 2, 5, 8, 11 ] > [ 3, 6, 9, 12 ]reshaped :( 2 6 ) > [ 1, 3, 5, 7, 9, 11 ] > [ 2, 4, 6, 8, 10, 12 ]
reshaped :( 4 3 ) > [ 1, 5, 9 ] > [ 2, 6, 10 ] > [ 3, 7, 11 ] > [ 4, 8, 12 ]
here is some data to shape :( 1 12 ) > [ 1, 2, 3, 4, 10, 20, 30, 40, 100, 200, 300, 400 ]
normally fills columns first :( 3 4 ) > [ 1, 4, 30, 200 ] > [ 2, 10, 40, 300 ] > [ 3, 20, 100, 400 ]
fill rows first :( 3 4 ) > [ 1, 2, 3, 4 ] > [ 10, 20, 30, 40 ] > [ 100, 200, 300, 400 ]
reshaped and reordered :( 4 3 ) > [ 1, 2, 3 ] > [ 4, 5, 6 ] > [ 7, 8, 9 ] > [ 10, 11, 12 ]
transposed :( 4 3 ) > [ 1, 2, 3 ] > [ 4, 5, 6 ] > [ 7, 8, 9 ] > [ 10, 11, 12 ]
bigger and padded and reordered :( 8 6 ) > [ 1, 2, 3, 4, 5, 6 ] > [ 7, 8, 9, 10, 11, 12 ] > [ -1, -2, -3, -1, -2, -3 ] > [ -1, -2, -3, -1, -2, -3 ] > [ -1, -2, -3, -1, -2, -3 ] > [ -1, -2, -3, -1, -2, -3 ] > [ -1, -2, -3, -1, -2, -3 ] > [ -1, -2, -3, -1, -2, -3 ]
STANDARD
Fortran 95
SEE ALSO
SHAPE(3), PACK(3), TRANSPOSE(3)
fortran-lang intrinsic descriptions (license: MIT) @urbanjost
| Nemo Release 3.1 | reshape (3fortran) | April 28, 2024 |
