pyrnm3.f

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C*********************************************************************
 
C...PYRNM3
C...Calculates the running of M3, the SU(3) gluino mass parameter.
 
      FUNCTION pyrnm3(RGUT)
 
C...Double precision and integer declarations.
      IMPLICIT DOUBLE PRECISION(a-h, o-z)
      IMPLICIT INTEGER(i-n)
      INTEGER pyk,pychge,pycomp
 
C...Local variables.
      DOUBLE PRECISION r
      DOUBLE PRECISION tol
      EXTERNAL pyalps
      DOUBLE PRECISION pyalps
      DATA tol/0.001d0/
      DATA r/0.61803399d0/
 
      c=1d0-r
 
      bx=rgut*pyalps(rgut**2)
      ax=min(50d0,bx*0.5d0)
      cx=max(2000d0,2d0*bx)
 
      x0=ax
      x3=cx
      IF(abs(cx-bx).GT.abs(bx-ax))THEN
        x1=bx
        x2=bx+c*(cx-bx)
      ELSE
        x2=bx
        x1=bx-c*(bx-ax)
      ENDIF
      as1=pyalps(x1**2)
      f1=abs(x1-rgut*as1)
      as2=pyalps(x2**2)
      f2=abs(x2-rgut*as2)
  100 IF(abs(x3-x0).GT.tol*(abs(x1)+abs(x2))) THEN
        IF(f2.LT.f1) THEN
          x0=x1
          x1=x2
          x2=r*x1+c*x3
          f1=f2
          as2=pyalps(x2**2)
          f2=abs(x2-rgut*as2)
        ELSE
          x3=x2
          x2=x1
          x1=r*x2+c*x0
          f2=f1
          as1=pyalps(x1**2)
          f1=abs(x1-rgut*as1)
        ENDIF
        goto 100
      ENDIF
      IF(f1.LT.f2) THEN
        pyrnm3=x1
        xmin=x1
      ELSE
        pyrnm3=x2
        xmin=x2
      ENDIF
 
      RETURN
      END