46 lines
1.2 KiB
Plaintext
46 lines
1.2 KiB
Plaintext
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MODULE NUMERICAL
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USE DECLARATIONS
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CONTAINS
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SUBROUTINE ELGS (A,N,INDX)
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! Subroutine to perform the partial-pivoting Gaussian elimination.
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! A(N,N) is the original matrix in the input and transformed matrix
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! plus the pivoting element ratios below the diagonal in the output.
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! INDX(N) records the pivoting order. Copyright (c) Tao Pang 2001.
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IMPLICIT NONE
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INTEGER, INTENT (IN) :: N
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INTEGER :: I,J,K,ITMP
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INTEGER, INTENT (OUT), DIMENSION (N) :: INDX
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REAL :: C1,PI,PI1,PJ
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REAL, INTENT (INOUT), DIMENSION (N,N) :: A
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REAL, DIMENSION (N) :: C
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WRITE(*,*) 'Calculating...'
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! Initialize the index
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DO I = 1, N
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INDX(I) = I
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END DO
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! Find the rescaling factors, one from each row
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DO I = 1, N
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C1= 0.0
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DO J = 1, N
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C1 = AMAX1(C1,ABS(A(I,J)))
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END DO
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C(I) = C1
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END DO
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! Search the pivoting (largest) element from each column
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DO J = 1, N-1
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PI1 = 0.0
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DO I = J, N
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PI = ABS(A(INDX(I),J))/C(INDX(I))
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IF (PI.GT.PI1) THEN
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PI1 = PI
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K = I
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ENDIF
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END DO
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! Search the pivoting (largest) element from each column
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! Interchange the rows via INDX(N) to record pivoting order
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! etc ....
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END DO
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END SUBROUTINE ELGS
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END MODULE NUMERICAL
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