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Manual Reference Pages  - spread (3fortran)

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NAME

SPREAD(3) - [ARRAY:CONSTRUCTION] Add a dimension and replicate data

SYNOPSIS

result = spread(source, dim, ncopies)

         TYPE(kind=KIND) function spread(source, dim, ncopies)

          TYPE(kind=KIND)             :: source(..)
          integer(kind=**),intent(in) :: dim
          integer(kind=**),intent(in) :: ncopies

CHARACTERISTICS

o	SOURCE is a scalar or array of any type and a rank less than fifteen.
o	DIM is an integer scalar
o	NCOPIES is an integer scalar

DESCRIPTION

SPREAD(3) replicates a SOURCE array along a specified dimension DIM. The copy is repeated NCOPIES times.

So to add additional rows to a matrix DIM=1 would be used, but to add additional rows DIM=2 would be used, for example.

If SOURCE is scalar, the size of the resulting vector is NCOPIES and each element of the result has a value equal to SOURCE.

OPTIONS

o	SOURCE : the input data to duplicate
o	DIM : The additional dimension value in the range from 1 to N+1, where N equals the rank of SOURCE.
o	NCOPIES : the number of copies of the original data to generate

RESULT

The result is an array of the same type as SOURCE and has rank N+1 where N equals the rank of SOURCE.

EXAMPLES

Sample program:

    program demo_spread
    implicit none

    integer a1(4,3), a2(3,4), v(4), s

       write(*,’(a)’ ) &
       ’TEST SPREAD(3)                                      ’, &
       ’  SPREAD(3) is a FORTRAN90 function which replicates’, &
       ’  an array by adding a dimension.                   ’, &
       ’ ’

       s = 99
       call printi(’suppose we have a scalar S’,s)

       write(*,*) ’to add a new dimension (1) of extent 4 call’
       call printi(’spread( s, dim=1, ncopies=4 )’,spread ( s, 1, 4 ))

       v = [ 1, 2, 3, 4 ]
       call printi(’ first we will set V to’,v)

       write(*,’(a)’)’ and then do "spread ( v, dim=2, ncopies=3 )"’
       a1 = spread ( v, dim=2, ncopies=3 )
       call printi(’uses v as a column and makes 3 columns’,a1)

       a2 = spread ( v, 1, 3 )
       call printi(’ spread(v,1,3) uses v as a row and makes 3 rows’,a2)

    contains
    ! CONVENIENCE ROUTINE; NOT DIRECTLY CONNECTED TO SPREAD(3)
    subroutine printi(title,a)
    use, intrinsic :: iso_fortran_env, only : stderr=>ERROR_UNIT,&
     & stdin=>INPUT_UNIT, stdout=>OUTPUT_UNIT
    implicit none

    !@(#) print small 2d integer scalar, vector, matrix in row-column format

    character(len=*),parameter   :: all=’(" ",*(g0,1x))’
    character(len=*),intent(in)  :: title
    character(len=20)            :: row
    integer,intent(in)           :: a(..)
    integer                      :: i

       write(*,all,advance=’no’)trim(title)
       ! select rank of input
       select rank(a)
       rank (0); write(*,’(a)’)’ (a scalar)’
          write(*,’(" > [ ",i0," ]")’)a
       rank (1); write(*,’(a)’)’ (a vector)’
          ! find how many characters to use for integers
          write(row,’(i0)’)ceiling(log10(max(1.0,real(maxval(abs(a))))))+2
          ! use this format to write a row
          row=’(" > [",*(i’//trim(row)//’:,","))’
          do i=1,size(a)
             write(*,fmt=row,advance=’no’)a(i)
             write(*,’(" ]")’)
          enddo
       rank (2); write(*,’(a)’)’ (a matrix) ’
          ! find how many characters to use for integers
          write(row,’(i0)’)ceiling(log10(max(1.0,real(maxval(abs(a))))))+2
          ! use this format to write a row
          row=’(" > [",*(i’//trim(row)//’:,","))’
          do i=1,size(a,dim=1)
             write(*,fmt=row,advance=’no’)a(i,:)
             write(*,’(" ]")’)
          enddo
       rank default
          write(stderr,*)’*printi* did not expect rank=’, rank(a), &
           & ’shape=’, shape(a),’size=’,size(a)
          stop ’*printi* unexpected rank’
       end select
       write(*,all) ’>shape=’,shape(a),’,rank=’,rank(a),’,size=’,size(a)
       write(*,*)

    end subroutine printi

    end program demo_spread

Results:

     > TEST SPREAD(3)
     >   SPREAD(3) is a FORTRAN90 function which replicates
     >   an array by adding a dimension.
     >
     >  suppose we have a scalar S  (a scalar)
     >  > [ 99 ]
     >  >shape= ,rank= 0 ,size= 1
     >
     >  to add a new dimension (1) of extent 4 call
     >  spread( s, dim=1, ncopies=4 )  (a vector)
     >  > [  99 ]
     >  > [  99 ]
     >  > [  99 ]
     >  > [   0 ]
     >  >shape= 4 ,rank= 1 ,size= 4
     >
     >   first we will set V to  (a vector)
     >  > [  1 ]
     >  > [  2 ]
     >  > [  3 ]
     >  > [  4 ]
     >  >shape= 4 ,rank= 1 ,size= 4
     >
     >  and then do "spread ( v, dim=2, ncopies=3 )"
     >  uses v as a column and makes 3 columns  (a matrix)
     >  > [  1,  1,  1 ]
     >  > [  2,  2,  2 ]
     >  > [  3,  3,  3 ]
     >  > [  4,  4,  4 ]
     >  >shape= 4 3 ,rank= 2 ,size= 12
     >
     >   spread(v,1,3) uses v as a row and makes 3 rows  (a matrix)
     >  > [  1,  2,  3,  4 ]
     >  > [  1,  2,  3,  4 ]
     >  > [  1,  2,  3,  4 ]
     >  >shape= 3 4 ,rank= 2 ,size= 12
     >

STANDARD

Fortran 95

SEE ALSO

MERGE(3), PACK(3), UNPACK(3)

fortran-lang intrinsic descriptions (license: MIT) @urbanjost

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Nemo Release 3.1

spread (3fortran)

April 28, 2024

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