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SUBROUTINE DTPMV(UPLO,TRANS,DIAG,N,AP,X,INCX)
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* .. Scalar Arguments ..
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CHARACTER DIAG,TRANS,UPLO
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* .. Array Arguments ..
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DOUBLE PRECISION AP(*),X(*)
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* DTPMV performs one of the matrix-vector operations
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* x := A*x, or x := A'*x,
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* where x is an n element vector and A is an n by n unit, or non-unit,
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* upper or lower triangular matrix, supplied in packed form.
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* On entry, UPLO specifies whether the matrix is an upper or
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* lower triangular matrix as follows:
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* UPLO = 'U' or 'u' A is an upper triangular matrix.
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* UPLO = 'L' or 'l' A is a lower triangular matrix.
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* TRANS - CHARACTER*1.
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* On entry, TRANS specifies the operation to be performed as
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* TRANS = 'N' or 'n' x := A*x.
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* TRANS = 'T' or 't' x := A'*x.
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* TRANS = 'C' or 'c' x := A'*x.
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* On entry, DIAG specifies whether or not A is unit
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* triangular as follows:
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* DIAG = 'U' or 'u' A is assumed to be unit triangular.
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* DIAG = 'N' or 'n' A is not assumed to be unit
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* On entry, N specifies the order of the matrix A.
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* N must be at least zero.
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* AP - DOUBLE PRECISION array of DIMENSION at least
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* ( ( n*( n + 1 ) )/2 ).
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* Before entry with UPLO = 'U' or 'u', the array AP must
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* contain the upper triangular matrix packed sequentially,
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* column by column, so that AP( 1 ) contains a( 1, 1 ),
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* AP( 2 ) and AP( 3 ) contain a( 1, 2 ) and a( 2, 2 )
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* respectively, and so on.
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* Before entry with UPLO = 'L' or 'l', the array AP must
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* contain the lower triangular matrix packed sequentially,
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* column by column, so that AP( 1 ) contains a( 1, 1 ),
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* AP( 2 ) and AP( 3 ) contain a( 2, 1 ) and a( 3, 1 )
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* respectively, and so on.
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* Note that when DIAG = 'U' or 'u', the diagonal elements of
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* A are not referenced, but are assumed to be unity.
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* X - DOUBLE PRECISION array of dimension at least
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* ( 1 + ( n - 1 )*abs( INCX ) ).
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* Before entry, the incremented array X must contain the n
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* element vector x. On exit, X is overwritten with the
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* tranformed vector x.
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* On entry, INCX specifies the increment for the elements of
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* X. INCX must not be zero.
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* Level 2 Blas routine.
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* -- Written on 22-October-1986.
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* Jack Dongarra, Argonne National Lab.
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* Jeremy Du Croz, Nag Central Office.
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* Sven Hammarling, Nag Central Office.
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* Richard Hanson, Sandia National Labs.
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PARAMETER (ZERO=0.0D+0)
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* .. Local Scalars ..
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DOUBLE PRECISION TEMP
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INTEGER I,INFO,IX,J,JX,K,KK,KX
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* .. External Functions ..
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* .. External Subroutines ..
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* Test the input parameters.
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IF (.NOT.LSAME(UPLO,'U') .AND. .NOT.LSAME(UPLO,'L')) THEN
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ELSE IF (.NOT.LSAME(TRANS,'N') .AND. .NOT.LSAME(TRANS,'T') .AND.
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+ .NOT.LSAME(TRANS,'C')) THEN
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ELSE IF (.NOT.LSAME(DIAG,'U') .AND. .NOT.LSAME(DIAG,'N')) THEN
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ELSE IF (N.LT.0) THEN
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ELSE IF (INCX.EQ.0) THEN
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CALL XERBLA('DTPMV ',INFO)
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* Quick return if possible.
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NOUNIT = LSAME(DIAG,'N')
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* Set up the start point in X if the increment is not unity. This
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* will be ( N - 1 )*INCX too small for descending loops.
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ELSE IF (INCX.NE.1) THEN
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* Start the operations. In this version the elements of AP are
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* accessed sequentially with one pass through AP.
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IF (LSAME(TRANS,'N')) THEN
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IF (LSAME(UPLO,'U')) THEN
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IF (X(J).NE.ZERO) THEN
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X(I) = X(I) + TEMP*AP(K)
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IF (NOUNIT) X(J) = X(J)*AP(KK+J-1)
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IF (X(JX).NE.ZERO) THEN
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DO 30 K = KK,KK + J - 2
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X(IX) = X(IX) + TEMP*AP(K)
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IF (NOUNIT) X(JX) = X(JX)*AP(KK+J-1)
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IF (X(J).NE.ZERO) THEN
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X(I) = X(I) + TEMP*AP(K)
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IF (NOUNIT) X(J) = X(J)*AP(KK-N+J)
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IF (X(JX).NE.ZERO) THEN
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DO 70 K = KK,KK - (N- (J+1)),-1
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X(IX) = X(IX) + TEMP*AP(K)
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IF (NOUNIT) X(JX) = X(JX)*AP(KK-N+J)
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IF (LSAME(UPLO,'U')) THEN
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IF (NOUNIT) TEMP = TEMP*AP(KK)
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TEMP = TEMP + AP(K)*X(I)
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IF (NOUNIT) TEMP = TEMP*AP(KK)
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DO 110 K = KK - 1,KK - J + 1,-1
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TEMP = TEMP + AP(K)*X(IX)
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IF (NOUNIT) TEMP = TEMP*AP(KK)
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TEMP = TEMP + AP(K)*X(I)
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IF (NOUNIT) TEMP = TEMP*AP(KK)
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DO 150 K = KK + 1,KK + N - J
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TEMP = TEMP + AP(K)*X(IX)