anchor.diff:        SUBROUTINE TRSTLP (N,M,A,B,RHO,DX,IFULL,IACT,Z,ZDOTA,VMULTC,
        1  SDIRN,DXNEW,VMULTD,IPRINT)
         IMPLICIT DOUBLE PRECISION (A-H,O-Z)
  +      DOUBLE PRECISION TEMP
         DIMENSION A(N,*),B(*),DX(*),IACT(*),Z(N,*),ZDOTA(*),
        1  VMULTC(*),SDIRN(*),DXNEW(*),VMULTD(*)
   C
  
positive.code: C     active set.
  C
        IF (IPRINT .EQ. 3) THEN
           PRINT *, 'TOT, NACT, ICON = ', TOT, NACT, ICON
        END IF
        IF (TOT .NE. 0.0d0) THEN
            NACT=NACT+1
  
negative.code:   470 VMULTC(K)=DMAX1(0.0d0,TEMP*VMULTC(K)+RATIO*VMULTD(K))
        PRINT *, '  3. VMULTC = ', (VMULTC(I),I=1,M+1)
        IF (MCON .EQ. M) RESMAX=RESOLD+RATIO*(RESMAX-RESOLD)
        PRINT *, ' RESMAX, MCON, M, ICON = ', 
       1    RESMAX, MCON, M, ICON
  C
  C     If the full step is not acceptable then begin another iteration.
  C     Otherwise switch to stage two or end the calculation.
  