subroutine sgbdi(abd,lda,n,ml,mu,ipvt,det) integer lda,n,ml,mu,ipvt(1) real abd(lda,1),det(2) c c sgbdi computes the determinant of a band matrix c using the factors computed by sgbco or sgbfa. c if the inverse is needed, use sgbsl n times. c c on entry c c abd real(lda, n) c the output from sgbco or sgbfa. c c lda integer c the leading dimension of the array abd . c c n integer c the order of the original matrix. c c ml integer c number of diagonals below the main diagonal. c c mu integer c number of diagonals above the main diagonal. c c ipvt integer(n) c the pivot vector from sgbco or sgbfa. c c on return c c det real(2) c determinant of original matrix. c determinant = det(1) * 10.0**det(2) c with 1.0 .le. abs(det(1)) .lt. 10.0 c or det(1) = 0.0 . 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 fortran abs c c internal variables c real ten integer i,m c c m = ml + mu + 1 det(1) = 1.0e0 det(2) = 0.0e0 ten = 10.0e0 do 50 i = 1, n if (ipvt(i) .ne. i) det(1) = -det(1) det(1) = abd(m,i)*det(1) c ...exit if (det(1) .eq. 0.0e0) go to 60 10 if (abs(det(1)) .ge. 1.0e0) go to 20 det(1) = ten*det(1) det(2) = det(2) - 1.0e0 go to 10 20 continue 30 if (abs(det(1)) .lt. ten) go to 40 det(1) = det(1)/ten det(2) = det(2) + 1.0e0 go to 30 40 continue 50 continue 60 continue return end