NCEPLIBS-w3emc/ver-2.9.2/w3reddat_8f_source.html

      subroutine w3reddat(it,rinc,dinc)

!$$$   SUBPROGRAM  DOCUMENTATION  BLOCK

!

! SUBPROGRAM: W3REDDAT       REDUCE A TIME INTERVAL TO A CANONICAL FORM

!   AUTHOR: MARK IREDELL     ORG: WP23       DATE: 98-01-05

!

! ABSTRACT: THIS SUBPROGRAM REDUCES AN NCEP RELATIVE TIME INTERVAL

!   INTO ONE OF SEVEN CANONICAL FORMS, DEPENDING ON THE INPUT IT VALUE.

!

!   First reduced format type (IT=-1):

!        RINC(1) is an arbitrary integer.

!        RINC(2) is an integer between 00 and 23, inclusive.

!        RINC(3) is an integer between 00 and 59, inclusive.

!        RINC(4) is an integer between 00 and 59, inclusive.

!        RINC(5) is an integer between 000 and 999, inclusive.

!      If RINC(1) is negative, then the time interval is negative.

!

!   Second reduced format type (IT=0):

!      If the time interval is not negative, then the format is:

!        RINC(1) is zero or a positive integer.

!        RINC(2) is an integer between 00 and 23, inclusive.

!        RINC(3) is an integer between 00 and 59, inclusive.

!        RINC(4) is an integer between 00 and 59, inclusive.

!        RINC(5) is an integer between 000 and 999, inclusive.

!      Otherwise if the time interval is negative, then the format is:

!        RINC(1) is zero or a negative integer.

!        RINC(2) is an integer between 00 and -23, inclusive.

!        RINC(3) is an integer between 00 and -59, inclusive.

!        RINC(4) is an integer between 00 and -59, inclusive.

!        RINC(5) is an integer between 000 and -999, inclusive.

!

!   Days format type (IT=1):

!        RINC(1) is arbitrary.

!        RINC(2) is zero.

!        RINC(3) is zero.

!        RINC(4) is zero.

!        RINC(5) is zero.

!

!   Hours format type (IT=2):

!        RINC(1) is zero.

!        RINC(2) is arbitrary.

!        RINC(3) is zero.

!        RINC(4) is zero.

!        RINC(5) is zero.

!      (This format should not express time intervals longer than 300 years.)

!

!   Minutes format type (IT=3):

!        RINC(1) is zero.

!        RINC(2) is zero.

!        RINC(3) is arbitrary.

!        RINC(4) is zero.

!        RINC(5) is zero.

!      (This format should not express time intervals longer than five years.)

!

!   Seconds format type (IT=4):

!        RINC(1) is zero.

!        RINC(2) is zero.

!        RINC(3) is zero.

!        RINC(4) is arbitrary.

!        RINC(5) is zero.

!      (This format should not express time intervals longer than one month.)

!

!   Milliseconds format type (IT=5):

!        RINC(1) is zero.

!        RINC(2) is zero.

!        RINC(3) is zero.

!        RINC(4) is zero.

!        RINC(5) is arbitrary.

!     (This format should not express time intervals longer than one hour.)

!

! PROGRAM HISTORY LOG:

!   98-01-05  MARK IREDELL

!

! USAGE:  CALL W3REDDAT(IT,RINC,DINC)

!

!   INPUT VARIABLES:

!     IT         INTEGER RELATIVE TIME INTERVAL FORMAT TYPE

!                (-1 FOR FIRST REDUCED TYPE (HOURS ALWAYS POSITIVE),

!                 0 FOR SECOND REDUCED TYPE (HOURS CAN BE NEGATIVE),

!                 1 FOR DAYS ONLY, 2 FOR HOURS ONLY, 3 FOR MINUTES ONLY,

!                 4 FOR SECONDS ONLY, 5 FOR MILLISECONDS ONLY)

!     RINC       REAL (5) NCEP RELATIVE TIME INTERVAL

!                (DAYS, HOURS, MINUTES, SECONDS, MILLISECONDS)

!

!   OUTPUT VARIABLES:

!     DINC       REAL (5) NCEP RELATIVE TIME INTERVAL

!                (DAYS, HOURS, MINUTES, SECONDS, MILLISECONDS)

!

! SUBPROGRAMS CALLED:

!

! ATTRIBUTES:

!   LANGUAGE: FORTRAN 90

!

!$$$

      real rinc(5),dinc(5)

!  parameters for number of units in a day

!  and number of milliseconds in a unit

!  and number of next smaller units in a unit, respectively

      integer,dimension(5),parameter:: itd=(/1,24,1440,86400,86400000/),

     &                                 itm=itd(5)/itd

      integer,dimension(4),parameter:: itn=itd(2:5)/itd(1:4)

      integer,parameter:: np=16

      integer iinc(4),jinc(5),kinc(5)

! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

!  first reduce to the first reduced form

      iinc=floor(rinc(1:4))

!  convert all positive fractional parts to milliseconds

!  and determine canonical milliseconds

      jinc(5)=nint(dot_product(rinc(1:4)-iinc,real(itm(1:4)))+rinc(5))

      kinc(5)=modulo(jinc(5),itn(4))

!  convert remainder to seconds and determine canonical seconds

      jinc(4)=iinc(4)+(jinc(5)-kinc(5))/itn(4)

      kinc(4)=modulo(jinc(4),itn(3))

!  convert remainder to minutes and determine canonical minutes

      jinc(3)=iinc(3)+(jinc(4)-kinc(4))/itn(3)

      kinc(3)=modulo(jinc(3),itn(2))

!  convert remainder to hours and determine canonical hours

      jinc(2)=iinc(2)+(jinc(3)-kinc(3))/itn(2)

      kinc(2)=modulo(jinc(2),itn(1))

!  convert remainder to days and compute milliseconds of the day

      kinc(1)=iinc(1)+(jinc(2)-kinc(2))/itn(1)

      ms=dot_product(kinc(2:5),itm(2:5))

! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

!  next reduce to either single value canonical form

!  or to one of the two reduced forms

      if(it.ge.1.and.it.le.5) then

!  ensure that exact multiples of 1./np are expressed exactly

!  (other fractions may have precision errors)

        rp=(np*ms)/itm(it)+mod(np*ms,itm(it))/real(itm(it))

        dinc=0

        dinc(it)=real(kinc(1))*itd(it)+rp/np

      else

!  the reduced form is done except the second reduced form is modified

!  for negative time intervals with fractional days

        dinc=kinc

        if(it.eq.0.and.kinc(1).lt.0.and.ms.gt.0) then

          dinc(1)=dinc(1)+1

          dinc(2:5)=mod(ms-itm(1),itm(1:4))/itm(2:5)

        endif

      endif

! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

      end