Random numbers. More...

Functions/Subroutines
subroutine	gbrshi (n, a)
	F.Gutbrod random number generator.

subroutine	gbrtim
	GBRSHI initialization using TIME().

real(mps) function	uran ()
	Random number U(0,1) using RANSHI.

real(mps) function	gran ()
	Gauss random number.

Detailed Description

Random numbers.

Author: Volker Blobel, University Hamburg, 2005-2009 (initial Fortran77 version); Claus Kleinwort, DESY (maintenance and developement)

Copyright: Copyright (c) 2009 - 2015 Deutsches Elektronen-Synchroton, Member of the Helmholtz Association, (DESY), HAMBURG, GERMANY

This library is free software; you can redistribute it and/or modify it under the terms of the GNU Library General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public License for more details.

You should have received a copy of the GNU Library General Public License along with this program (see the file COPYING.LIB for more details); if not, write to the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

Random number generators for Uniform and Normal distribution:

URAN() for U(0,1)
GRAN() for N(0,1)

Definition in file randoms.f90.

Function/Subroutine Documentation

◆ gbrshi()

subroutine gbrshi	(	integer(mpi), intent(in)	n,
		real(mps), dimension(*), intent(out)	a
	)

F.Gutbrod random number generator.

Return N random numbers U(0,1) in array A(N). Initialization by entry GBRVIN.

Parameters

[in]	n	number of requested random number
[out]	a	array of requested random number

Definition at line 40 of file randoms.f90.

    USE mpdef
 
    IMPLICIT NONE
    INTEGER(mpi) :: i
    INTEGER(mpi) :: ian
    INTEGER(mpi) :: iboost
    INTEGER(mpi) :: ic
    INTEGER(mpi) :: idum
    INTEGER(mpi) :: irotor
    INTEGER(mpi) :: iseed
    INTEGER(mpi) :: it
    INTEGER(mpi) :: iwarm
    INTEGER(mpi) :: j
    INTEGER(mpi) :: jseed
    INTEGER(mpi) :: jwarm
    INTEGER(mpi) :: k
    INTEGER(mpi) :: m
    INTEGER(mpi) :: mbuff
 
    INTEGER(mpi), INTENT(IN)                      :: n
    REAL(mps), INTENT(OUT)                        :: a(*)
    INTEGER(mpi), PARAMETER :: nb=511
    INTEGER(mpi), PARAMETER :: ia=16807
    INTEGER(mpi), PARAMETER :: im=2147483647
    INTEGER(mpi), PARAMETER :: iq=127773
    INTEGER(mpi), PARAMETER :: ir=2836
    REAL(mps), PARAMETER :: aeps=1.0e-10
    REAL(mps), PARAMETER :: scalin=4.6566125e-10
    common/ranbuf/mbuff(0:nb),ian,ic,iboost
 
    INTEGER(mpi) :: istart
 
    irotor(m,n)=ieor(ior(ishft(m,17),ishft(m,-15)),n)
    DATA istart/0/,iwarm/10/,iseed/4711/
    IF(istart /= 0) GO TO 20
    WRITE(*,*) ' Automatic GBRSHI initialization using:'
    !     initialize buffer
10  idum=iseed+9876543          ! prevent damage, if iseed=0
    WRITE(*,*) '           ISEED=',iseed,'   IWARM=',iwarm
    DO j=0,nb+1                 ! fill buffer
        k=idum/iq                  ! minimal standard generator
        idum=ia*(idum-k*iq)-ir*k   !    with Schrages method
        IF(idum < 0) idum=idum+im !
        mbuff(j)=ishft(idum,1)     ! fill in leading bit
    END DO
    ian=iand(ian,nb)            ! mask angle
    ic=1                        ! set pointer
    iboost=0
    DO j=1,iwarm*nb             ! warm up a few times
        it=mbuff(ian)              ! hit ball angle
        mbuff(ian)=irotor(it,ic)   ! new spin
        ic=it                      ! replace red spin
        ian=iand(it+iboost,nb)     ! boost and mask angle
        iboost=iboost+1            ! increment boost
    END DO
    IF(istart < 0) RETURN      ! return for RBNVIN
    istart=1                    ! set done-flag
    !     generate array of r.n.
    20   DO i=1,n
        it=mbuff(ian)              ! hit ball angle
        mbuff(ian)=irotor(it,ic)   ! new spin
        ic=it                      ! replace red spin
        ian=iand(it+iboost,nb)     ! boost and mask angle
        a(i)=real(ishft(it,-1),mps)*scalin+aeps ! avoid zero output
        iboost=iboost+1            ! increment boost
    END DO
    iboost=iand(iboost,nb)
    RETURN
 
    entry gbrvin(jseed,jwarm)   ! initialize, but only once
    IF(istart == 0) THEN
        WRITE(*,*) ' Gbrshi initialization by GBRVIN-call using:'
        iseed=jseed              ! copy seed and
        iwarm=jwarm              ! warm-up parameter
        istart=-1                ! start flag
        GO TO 10
    END IF

◆ gbrtim()

subroutine gbrtim

GBRSHI initialization using TIME().

Definition at line 121 of file randoms.f90.

    USE mpdef
 
    IMPLICIT NONE
    INTEGER(mpi) :: jseed
    REAL(mps) :: time
 
    LOGICAL :: done
    DATA    done/.false./
    IF(done) RETURN
    jseed=time()
    WRITE(*,*) ' Gbrshi initialialization using Time()'
    CALL gbrvin(jseed,10)
    done=.true.

◆ gran()

real(mps) function gran

Gauss random number.

Returns: random number N(0,1)

Definition at line 161 of file randoms.f90.

    USE mpdef
 
    IMPLICIT NONE
    REAL(mps) :: al
    REAL(mps) :: cs
    INTEGER(mpi) :: indx
    INTEGER(mpi) :: kn
    INTEGER(mpi) :: ndim
    REAL(mps) :: radsq
    REAL(mps) :: rn1
    REAL(mps) :: rn2
    REAL(mps) :: sn
 
    parameter(ndim=100)
    REAL(mps) :: buffer(ndim)
    DATA indx/ndim/,kn/1/
    SAVE indx,buffer,kn,cs,al
    !     ...
    IF(kn <= 1) THEN
        !        two U(-1,+1) random numbers
10      indx=mod(indx,ndim)+2
        IF(indx == 2) CALL gbrshi(ndim,buffer)
        rn1=buffer(indx-1)-1.0+buffer(indx-1)
        rn2=buffer(indx  )-1.0+buffer(indx)
        radsq=rn1*rn1+rn2*rn2
        IF(radsq > 1.0) GO TO 10 ! test point inside circle?
        !        sine and cosine for random phi
        sn=rn1/sqrt(radsq)
        cs=rn2/sqrt(radsq)
        !        transform to gaussians
        al=sqrt(-2.0*log(radsq))
        kn =2
        gran=sn*al
    ELSE
        kn =1
        gran=cs*al
    END IF

◆ uran()

real(mps) function uran

Random number U(0,1) using RANSHI.

Returns: random number U(0,1)

Definition at line 141 of file randoms.f90.