root / src / gaussj.f90 @ 2
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SUBROUTINE gaussj(a,n,np,b,m,mp) |
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IMPLICIT NONE |
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INTEGER, PARAMETER :: KINT=KIND(1) |
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INTEGER, PARAMETER :: KREAL=KIND(1.0D0) |
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INTEGER(KINT) :: m,mp,n,np,NMAX |
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REAL(KREAL) :: a(np,np),b(np,mp) |
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PARAMETER (NMAX=50) |
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INTEGER(KINT) :: i,icol,irow,j,k,l,ll,indxc(NMAX),indxr(NMAX),ipiv(NMAX) |
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REAL(KREAL) :: big,dum,pivinv |
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do 11 j=1,n |
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ipiv(j)=0 |
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11 continue |
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do 22 i=1,n |
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big=0.d0 |
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do 13 j=1,n |
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if(ipiv(j).ne.1)then |
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do 12 k=1,n |
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if (ipiv(k).eq.0) then |
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if (abs(a(j,k)).ge.big)then |
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big=abs(a(j,k)) |
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irow=j |
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icol=k |
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endif |
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else if (ipiv(k).gt.1) then |
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pause 'singular matrix in gaussj' |
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endif |
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12 continue |
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endif |
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13 continue |
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ipiv(icol)=ipiv(icol)+1 |
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if (irow.ne.icol) then |
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do 14 l=1,n |
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dum=a(irow,l) |
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a(irow,l)=a(icol,l) |
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a(icol,l)=dum |
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14 continue |
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do 15 l=1,m |
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dum=b(irow,l) |
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b(irow,l)=b(icol,l) |
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b(icol,l)=dum |
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15 continue |
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endif |
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indxr(i)=irow |
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indxc(i)=icol |
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if (a(icol,icol).eq.0.d0) pause 'singular matrix in gaussj' |
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pivinv=1.d0/a(icol,icol) |
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a(icol,icol)=1.d0 |
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do 16 l=1,n |
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a(icol,l)=a(icol,l)*pivinv |
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16 continue |
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do 17 l=1,m |
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b(icol,l)=b(icol,l)*pivinv |
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17 continue |
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do 21 ll=1,n |
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if(ll.ne.icol)then |
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dum=a(ll,icol) |
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a(ll,icol)=0.d0 |
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do 18 l=1,n |
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a(ll,l)=a(ll,l)-a(icol,l)*dum |
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18 continue |
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do 19 l=1,m |
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b(ll,l)=b(ll,l)-b(icol,l)*dum |
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19 continue |
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endif |
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21 continue |
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22 continue |
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do 24 l=n,1,-1 |
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if(indxr(l).ne.indxc(l))then |
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do 23 k=1,n |
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dum=a(k,indxr(l)) |
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a(k,indxr(l))=a(k,indxc(l)) |
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a(k,indxc(l))=dum |
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23 continue |
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endif |
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24 continue |
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return |
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END |