SUBROUTINE SLVDJI(IOPT,B,R,NEQ,IHALFB,NDIM,MDIM)
C
C   ASYMMETRIC BAND MATRIX EQUATION SOLVER
C   DOCTORED TO IGNORE ZEROS IN LU DECOMP. STEP
C
C   IOPT=1 TRIANGULARIZES THE BAND MATRIX B
C   IOPT=2 SOLVES FOR RIGHT SIDE R, SOLUTION RETURNS IN R
C   IOPT=3 Performs IOPT = 1 THEN IOPT = 2 before returning
C
C    MODIFICATIONS - DOUBLE PRECISION ON ALL REAL VARIABLES
C                  - REVERSE ROW COLUMN ORDERING - I.E. J,I
C
      implicit double precision (a-h,o-z)
      DIMENSION B(MDIM,NDIM),R(NDIM)
      NRS=NEQ-1
      IHBP=IHALFB+1
      IF (IOPT.EQ.2) GO TO 30
C
C  TRIANGULARIZE MATRIX A USING DOOLITTLE METHOD
C
      DO 10 K=1,NRS
      PIVOT=B(IHBP,K)
      PD = 1./PIVOT
C             MULTIPLY IS FASTER THAN DIVIDE
      KK=K+1
      KC=IHBP
      DO 21 I=KK,NEQ
      KC=KC-1
      IF(KC.LE.0) GO TO 10
      C=-B(KC,I)*PD
      IF (C.EQ.0.0) GO TO 21
      B(KC,I)=C
      KI=KC+1
      LIM=KC+IHALFB
      DO 20 J=KI,LIM
      JC=IHBP+J-KC
   20 B(J,I)=B(J,I)+C*B(JC,K)
   21 CONTINUE
   10 CONTINUE
      IF(IOPT.EQ.1)GO TO 100
C
C  MODIFY LOAD VECTOR R
C
   30 NN=NEQ+1
      IBAND=2*IHALFB+1
      DO 40 I=2,NEQ
      JC=IHBP-I+1
      JI=1
      IF (JC.LE.0) GO TO 50
      GO TO 60
   50 JC=1
      JI=I-IHBP+1
   60 SUM=0.0
      DO 70 J=JC,IHALFB
      SUM=SUM+B(J,I)*R(JI)
   70 JI=JI+1
   40 R(I)=R(I)+SUM
C
C   BACK SOLUTION
C
      R(NEQ)=R(NEQ)/B(IHBP,NEQ)
      DO 80 IBACK=2,NEQ
      I=NN-IBACK
      JP=I
      KR=IHBP+1
      MR=MIN0(IBAND,IHALFB+IBACK)
      SUM=0.0
      DO 90 J=KR,MR
      JP=JP+1
   90 SUM=SUM+B(J,I)*R(JP)
   80 R(I)=(R(I)-SUM)/B(IHBP,I)
  100 RETURN
      END