Previous: spoco Up: ../linpack.html Next: spofa
SUBROUTINE SPODI(A,LDA,N,DET,JOB)
INTEGER LDA,N,JOB
REAL A(LDA,1)
REAL DET(2)
C
C SPODI COMPUTES THE DETERMINANT AND INVERSE OF A CERTAIN
C REAL SYMMETRIC POSITIVE DEFINITE MATRIX (SEE BELOW)
C USING THE FACTORS COMPUTED BY SPOCO, SPOFA OR SQRDC.
C
C ON ENTRY
C
C A REAL(LDA, N)
C THE OUTPUT A FROM SPOCO OR SPOFA
C OR THE OUTPUT X FROM SQRDC.
C
C LDA INTEGER
C THE LEADING DIMENSION OF THE ARRAY A .
C
C N INTEGER
C THE ORDER OF THE MATRIX A .
C
C JOB INTEGER
C = 11 BOTH DETERMINANT AND INVERSE.
C = 01 INVERSE ONLY.
C = 10 DETERMINANT ONLY.
C
C ON RETURN
C
C A IF SPOCO OR SPOFA WAS USED TO FACTOR A THEN
C SPODI PRODUCES THE UPPER HALF OF INVERSE(A) .
C IF SQRDC WAS USED TO DECOMPOSE X THEN
C SPODI PRODUCES THE UPPER HALF OF INVERSE(TRANS(X)*X)
C WHERE TRANS(X) IS THE TRANSPOSE.
C ELEMENTS OF A BELOW THE DIAGONAL ARE UNCHANGED.
C IF THE UNITS DIGIT OF JOB IS ZERO, A IS UNCHANGED.
C
C DET REAL(2)
C DETERMINANT OF A OR OF TRANS(X)*X IF REQUESTED.
C OTHERWISE NOT REFERENCED.
C DETERMINANT = DET(1) * 10.0**DET(2)
C WITH 1.0 .LE. DET(1) .LT. 10.0
C OR DET(1) .EQ. 0.0 .
C
C ERROR CONDITION
C
C A DIVISION BY ZERO WILL OCCUR IF THE INPUT FACTOR CONTAINS
C A ZERO ON THE DIAGONAL AND THE INVERSE IS REQUESTED.
C IT WILL NOT OCCUR IF THE SUBROUTINES ARE CALLED CORRECTLY
C AND IF SPOCO OR SPOFA HAS SET INFO .EQ. 0 .
C
C LINPACK. THIS VERSION DATED 08/14/78 .
C CLEVE MOLER, UNIVERSITY OF NEW MEXICO, ARGONNE NATIONAL LAB.
C
C SUBROUTINES AND FUNCTIONS
C
C BLAS SAXPY,SSCAL
C FORTRAN MOD
C