SUBROUTINE DERIV

COMMON /DELTA1/ IRSS

COMMON /DELTA3/ IDET,ILATNO

COMMON /DELTA4/ IDERIV,IFINIS,IQMATF

COMMON /INVER1/ UI1,VI1,WI1,UI2,VI2,WI2,UI3,VI3,WI3

COMMON /MATR1/ U1,V1,W1,U2,V2,W2,U3,V3,W3

COMMON /QMAT/ ISQ11(519),ISQ12(519),ISQ13(519),

$ ISQ22(519),ISQ23(519),ISQ33(519)

C

C

C SUBROUTINE 'DERIV' ...

C FIND MATRIX TO CALCULATE DERIVATIVE LATTICE

C

C

C

C --- INITIALIZE VARIABLES FOR EACH NEW PROBLEM

IF(IDERIV.NE.1) GO TO 100

IDET = 0

IFINIS = 0

ILATNO = 0

100 CONTINUE

C

C --- INCREMENT DERIVATIVE LATTICE NUMBER, AND COUNT THE NUMBER

C OF UPPER TRIANGULAR MATRICES SELECTED (IDERIV = IQMATF WHEN

C LAST MATRIX IS SELECTED)

ILATNO = ILATNO + 1

IDERIV = IDERIV + 1

C

C --- SELECT AN UPPER TRIANGULAR MATRIX

U1 = ISQ11(IDERIV-1)

V1 = ISQ12(IDERIV-1)

W1 = ISQ13(IDERIV-1)

U2 = 0.0

V2 = ISQ22(IDERIV-1)

W2 = ISQ23(IDERIV-1)

U3 = 0.0

V3 = 0.0

W3 = ISQ33(IDERIV-1)

C

C --- CALCULATE DETERMINANT FOR UPPER TRIANGULAR MATRIX

C (SAVE PREVIOUS VALUE FOR LATER COMPARISON)

IDPRE = IDET

DET = U1*V2*W3 + V1*W2*U3 + W1*U2*V3 - U3*V2*W1 - V3*W2*U1 -

$ W3*U2*V1

IDET = NINT(DET)

C

C --- DO NOT CALCULATE THE TRANSPOSE OF THE INVERSE FOR THE UPPER

C TRIANGULAR MATRIX WHEN SUPERCELLS ARE BEING CALCULATED

C (WHEN BOTH SUPERCELL AND SUBCELL CALCULATIONS ARE TO BE

C DONE, SUPERCELLS ARE CALCULATED FIRST)

IF(IRSS.EQ.1.OR.IRSS.EQ.3) GO TO 300

C

C --- CALCULATE THE TRANSPOSE OF THE INVERSE FOR AN UPPER

C TRIANGULAR MATRIX (USED FOR CALCULATING SUBCELLS)

CALL INVERS(0)

U1 = UI1

V1 = UI2

W1 = UI3

U2 = VI1

V2 = VI2

W2 = VI3

U3 = WI1

V3 = WI2

W3 = WI3

300 CONTINUE

C

C --- CHECK FOR A CHANGE IN THE VALUE OF THE DETERMINANT OF

C THE UPPER TRIANGULAR MATRIX ... ENABLES APPROPRIATE

C SUB-HEADING TO BE WRITTEN

IF(IDET.EQ.IDPRE) GO TO 400

C

C --- CHANGE IN DELTA ENCOUNTERED ... WRITE SUB-HEADING FOR

C DERIVATIVE LATTICES

ILATNO = 1

IF(IRSS.NE.2) CALL OUTPT1(7)

IF(IRSS.EQ.2) CALL OUTPT1(8)

400 CONTINUE

C

C --- WRITE DERIVATIVE LATTICE NUMBER AND TRANSFORMATION MATRIX

C TO DERIVATIVE CELL

CALL OUTPT1(9)

CALL OUTPT1(10)

C

C --- ONLY WHEN THE LAST UPPER TRIANGULAR MATRIX HAS BEEN SELECTED,

C INITIALIZE VARIABLES FOR THE NEXT PROBLEM, OR FOR THE SUBCELL

C CALCULATIONS WHEN BOTH SUPERCELL AND SUBCELL CALCULATIONS ARE

C ARE TO BE DONE

IF(IDERIV-1.LT.IQMATF) GO TO 700

C

C --- LAST UPPER TRIANGULAR MATRIX, CHECK IF FINISHED PROBLEM

IF(IRSS.NE.3) IFINIS = 1

IF(IRSS.NE.3) GO TO 700

C

C --- FINISHED SUPERCELLS, INITIALIZE VARIABLES FOR SUBCELL

C CALCULATION ON NEXT CALL TO SUBROUTINE 'DERIV'

IRSS = 2

IDET = 0

IDERIV = 1

ILATNO = 0

700 CONTINUE

RETURN

END