SLATEC Routines --- CPZERO ---

*DECK CPZERO
      SUBROUTINE CPZERO (IN, A, R, T, IFLG, S)
C***BEGIN PROLOGUE  CPZERO
C***PURPOSE  Find the zeros of a polynomial with complex coefficients.
C***LIBRARY   SLATEC
C***CATEGORY  F1A1B
C***TYPE      COMPLEX (RPZERO-S, CPZERO-C)
C***KEYWORDS  POLYNOMIAL ROOTS, POLYNOMIAL ZEROS, REAL ROOTS
C***AUTHOR  Kahaner, D. K., (NBS)
C***DESCRIPTION
C
C      Find the zeros of the complex polynomial
C         P(Z)= A(1)*Z**N + A(2)*Z**(N-1) +...+ A(N+1)
C
C    Input...
C       IN = degree of P(Z)
C       A = complex vector containing coefficients of P(Z),
C            A(I) = coefficient of Z**(N+1-i)
C       R = N word complex vector containing initial estimates for zeros
C            if these are known.
C       T = 4(N+1) word array used for temporary storage
C       IFLG = flag to indicate if initial estimates of
C              zeros are input.
C            If IFLG .EQ. 0, no estimates are input.
C            If IFLG .NE. 0, the vector R contains estimates of
C               the zeros
C       ** WARNING ****** If estimates are input, they must
C                         be separated, that is, distinct or
C                         not repeated.
C       S = an N word array
C
C    Output...
C       R(I) = Ith zero,
C       S(I) = bound for R(I) .
C       IFLG = error diagnostic
C    Error Diagnostics...
C       If IFLG .EQ. 0 on return, all is well
C       If IFLG .EQ. 1 on return, A(1)=0.0 or N=0 on input
C       If IFLG .EQ. 2 on return, the program failed to converge
C                after 25*N iterations.  Best current estimates of the
C                zeros are in R(I).  Error bounds are not calculated.
C
C***REFERENCES  (NONE)
C***ROUTINES CALLED  CPEVL
C***REVISION HISTORY  (YYMMDD)
C   810223  DATE WRITTEN
C   890531  Changed all specific intrinsics to generic.  (WRB)
C   890531  REVISION DATE from Version 3.2
C   891214  Prologue converted to Version 4.0 format.  (BAB)
C***END PROLOGUE  CPZERO