anchor.diff:       M       XOUT5,XOUT4,XERR,DN_S,DN,
        O       IDSDT,XPT,TPT,I1,I2,I3)
   CMWF        NPATH(IPT)=KPATH
  +        IF (IVERBOSE.GE.5) THEN
   C MWF DEBUG
  -C        WRITE(LU_O,*)' AFTER ELTRACK ELEMENT LOOP T= ',T,
  -C     &       ' IDSDT= ',IDSDT,' TPT= ',TPT(IPT),' IPT= ',IPT,' M= ',M
  -C        WRITE(LU_O,*)' I1= ',I1,' I2= ',I2,' I3= ',I3
  -C        DO K=1,NEQ
  -C           WRITE(LU_O,*)' XPT(',K,',',IPT,')= ',XPT(K + IPT*MAXEQ)
  -C        ENDDO
  +           WRITE(LU_O,*)' AFTER ELTRACK ELEMENT LOOP T= ',T,
  +     &          ' IDSDT= ',IDSDT,' TPT= ',TPT(IPT),' IPT= ',IPT,' M= ',M
  +           WRITE(LU_O,*)' I1= ',I1,' I2= ',I2,' I3= ',I3
  +           DO K=1,NEQ
  +              WRITE(LU_O,*)' XPT(',K,',',IPT,')= ',XPT(K + IPT*MAXEQ)
  +           ENDDO
  +        ENDIF
   C
           IF(IDSDT.EQ.-1)THEN
             MPT(IPT)=M
  
positive.code: C FOR NOW WE KNOW THIS AS INPUT
  C
  C MWF DEBUG
  C        WRITE(LU_O,*)' B4 ELTRACK ELEMENT LOOP T= ',T,' TPT= ',TPT(IPT),
  C     &       ' IPT= ',IPT,' M= ',M
  C        WRITE(LU_O,*)' XS= ',(XS(I),I=1,NEQ)
          CALL EL_VEL_PREP(MAXND,MAXEQ,NNDE,
       &         NNP,NEL,NODE,NEQ,M,IDVE,DIR,
       &         XG,IE,VTL2G,VT1E,VT2E,XW,VT1W,VT2W)
  
negative.code: C     HAVE TO TREAT AS FLAT ARRAY, SINCE MAY BE DIFFERENT SHAPES IN PYTHON (q, versus ebqe)
  C     ASSUME MPT,TPT SET BY CALLING CODE 
  CMWF DEBUG
        IF (IVERBOSE.GE.1) THEN
           WRITE(LU_O,*)'ENTERING PT123'
           WRITE(LU_O,*)'NNP= ',NNP,' NEL= ',NEL,' NNDE= ',NNDE,' NEQ= ',
       &        NEQ,' NPT= ',NPT,' IBF= ',IBF,' LU_O= ',LU_O, ' ATOL= ',
       &        ATOL,' RTOL= ',RTOL, ' SF= ',SF, 'DN_SAFE= ',DN_SAFE
        ENDIF
        DO IPT=1,NPT
           DO I=1,NEQ
              XS(I)=X_I(I + MAXEQ*(IPT-1))
  