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SUBROUTINE <a name="CTPSV.1"></a><a href="ctpsv.f.html#CTPSV.1">CTPSV</a>(UPLO,TRANS,DIAG,N,AP,X,INCX)
<span class="comment">*</span><span class="comment"> .. Scalar Arguments ..
</span> INTEGER INCX,N
CHARACTER DIAG,TRANS,UPLO
<span class="comment">*</span><span class="comment"> ..
</span><span class="comment">*</span><span class="comment"> .. Array Arguments ..
</span> COMPLEX AP(*),X(*)
<span class="comment">*</span><span class="comment"> ..
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> Purpose
</span><span class="comment">*</span><span class="comment"> =======
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> <a name="CTPSV.13"></a><a href="ctpsv.f.html#CTPSV.1">CTPSV</a> solves one of the systems of equations
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> A*x = b, or A'*x = b, or conjg( A' )*x = b,
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> where b and x are n element vectors and A is an n by n unit, or
</span><span class="comment">*</span><span class="comment"> non-unit, upper or lower triangular matrix, supplied in packed form.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> No test for singularity or near-singularity is included in this
</span><span class="comment">*</span><span class="comment"> routine. Such tests must be performed before calling this routine.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> Arguments
</span><span class="comment">*</span><span class="comment"> ==========
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> UPLO - CHARACTER*1.
</span><span class="comment">*</span><span class="comment"> On entry, UPLO specifies whether the matrix is an upper or
</span><span class="comment">*</span><span class="comment"> lower triangular matrix as follows:
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> UPLO = 'U' or 'u' A is an upper triangular matrix.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> UPLO = 'L' or 'l' A is a lower triangular matrix.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> Unchanged on exit.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> TRANS - CHARACTER*1.
</span><span class="comment">*</span><span class="comment"> On entry, TRANS specifies the equations to be solved as
</span><span class="comment">*</span><span class="comment"> follows:
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> TRANS = 'N' or 'n' A*x = b.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> TRANS = 'T' or 't' A'*x = b.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> TRANS = 'C' or 'c' conjg( A' )*x = b.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> Unchanged on exit.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> DIAG - CHARACTER*1.
</span><span class="comment">*</span><span class="comment"> On entry, DIAG specifies whether or not A is unit
</span><span class="comment">*</span><span class="comment"> triangular as follows:
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> DIAG = 'U' or 'u' A is assumed to be unit triangular.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> DIAG = 'N' or 'n' A is not assumed to be unit
</span><span class="comment">*</span><span class="comment"> triangular.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> Unchanged on exit.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> N - INTEGER.
</span><span class="comment">*</span><span class="comment"> On entry, N specifies the order of the matrix A.
</span><span class="comment">*</span><span class="comment"> N must be at least zero.
</span><span class="comment">*</span><span class="comment"> Unchanged on exit.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> AP - COMPLEX array of DIMENSION at least
</span><span class="comment">*</span><span class="comment"> ( ( n*( n + 1 ) )/2 ).
</span><span class="comment">*</span><span class="comment"> Before entry with UPLO = 'U' or 'u', the array AP must
</span><span class="comment">*</span><span class="comment"> contain the upper triangular matrix packed sequentially,
</span><span class="comment">*</span><span class="comment"> column by column, so that AP( 1 ) contains a( 1, 1 ),
</span><span class="comment">*</span><span class="comment"> AP( 2 ) and AP( 3 ) contain a( 1, 2 ) and a( 2, 2 )
</span><span class="comment">*</span><span class="comment"> respectively, and so on.
</span><span class="comment">*</span><span class="comment"> Before entry with UPLO = 'L' or 'l', the array AP must
</span><span class="comment">*</span><span class="comment"> contain the lower triangular matrix packed sequentially,
</span><span class="comment">*</span><span class="comment"> column by column, so that AP( 1 ) contains a( 1, 1 ),
</span><span class="comment">*</span><span class="comment"> AP( 2 ) and AP( 3 ) contain a( 2, 1 ) and a( 3, 1 )
</span><span class="comment">*</span><span class="comment"> respectively, and so on.
</span><span class="comment">*</span><span class="comment"> Note that when DIAG = 'U' or 'u', the diagonal elements of
</span><span class="comment">*</span><span class="comment"> A are not referenced, but are assumed to be unity.
</span><span class="comment">*</span><span class="comment"> Unchanged on exit.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> X - COMPLEX array of dimension at least
</span><span class="comment">*</span><span class="comment"> ( 1 + ( n - 1 )*abs( INCX ) ).
</span><span class="comment">*</span><span class="comment"> Before entry, the incremented array X must contain the n
</span><span class="comment">*</span><span class="comment"> element right-hand side vector b. On exit, X is overwritten
</span><span class="comment">*</span><span class="comment"> with the solution vector x.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> INCX - INTEGER.
</span><span class="comment">*</span><span class="comment"> On entry, INCX specifies the increment for the elements of
</span><span class="comment">*</span><span class="comment"> X. INCX must not be zero.
</span><span class="comment">*</span><span class="comment"> Unchanged on exit.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> Level 2 Blas routine.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> -- Written on 22-October-1986.
</span><span class="comment">*</span><span class="comment"> Jack Dongarra, Argonne National Lab.
</span><span class="comment">*</span><span class="comment"> Jeremy Du Croz, Nag Central Office.
</span><span class="comment">*</span><span class="comment"> Sven Hammarling, Nag Central Office.
</span><span class="comment">*</span><span class="comment"> Richard Hanson, Sandia National Labs.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> .. Parameters ..
</span> COMPLEX ZERO
PARAMETER (ZERO= (0.0E+0,0.0E+0))
<span class="comment">*</span><span class="comment"> ..
</span><span class="comment">*</span><span class="comment"> .. Local Scalars ..
</span> COMPLEX TEMP
INTEGER I,INFO,IX,J,JX,K,KK,KX
LOGICAL NOCONJ,NOUNIT
<span class="comment">*</span><span class="comment"> ..
</span><span class="comment">*</span><span class="comment"> .. External Functions ..
</span> LOGICAL <a name="LSAME.111"></a><a href="lsame.f.html#LSAME.1">LSAME</a>
EXTERNAL <a name="LSAME.112"></a><a href="lsame.f.html#LSAME.1">LSAME</a>
<span class="comment">*</span><span class="comment"> ..
</span><span class="comment">*</span><span class="comment"> .. External Subroutines ..
</span> EXTERNAL <a name="XERBLA.115"></a><a href="xerbla.f.html#XERBLA.1">XERBLA</a>
<span class="comment">*</span><span class="comment"> ..
</span><span class="comment">*</span><span class="comment"> .. Intrinsic Functions ..
</span> INTRINSIC CONJG
<span class="comment">*</span><span class="comment"> ..
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> Test the input parameters.
</span><span class="comment">*</span><span class="comment">
</span> INFO = 0
IF (.NOT.<a name="LSAME.124"></a><a href="lsame.f.html#LSAME.1">LSAME</a>(UPLO,<span class="string">'U'</span>) .AND. .NOT.<a name="LSAME.124"></a><a href="lsame.f.html#LSAME.1">LSAME</a>(UPLO,<span class="string">'L'</span>)) THEN
INFO = 1
ELSE IF (.NOT.<a name="LSAME.126"></a><a href="lsame.f.html#LSAME.1">LSAME</a>(TRANS,<span class="string">'N'</span>) .AND. .NOT.<a name="LSAME.126"></a><a href="lsame.f.html#LSAME.1">LSAME</a>(TRANS,<span class="string">'T'</span>) .AND.
+ .NOT.<a name="LSAME.127"></a><a href="lsame.f.html#LSAME.1">LSAME</a>(TRANS,<span class="string">'C'</span>)) THEN
INFO = 2
ELSE IF (.NOT.<a name="LSAME.129"></a><a href="lsame.f.html#LSAME.1">LSAME</a>(DIAG,<span class="string">'U'</span>) .AND. .NOT.<a name="LSAME.129"></a><a href="lsame.f.html#LSAME.1">LSAME</a>(DIAG,<span class="string">'N'</span>)) THEN
INFO = 3
ELSE IF (N.LT.0) THEN
INFO = 4
ELSE IF (INCX.EQ.0) THEN
INFO = 7
END IF
IF (INFO.NE.0) THEN
CALL <a name="XERBLA.137"></a><a href="xerbla.f.html#XERBLA.1">XERBLA</a>(<span class="string">'<a name="CTPSV.137"></a><a href="ctpsv.f.html#CTPSV.1">CTPSV</a> '</span>,INFO)
RETURN
END IF
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> Quick return if possible.
</span><span class="comment">*</span><span class="comment">
</span> IF (N.EQ.0) RETURN
<span class="comment">*</span><span class="comment">
</span> NOCONJ = <a name="LSAME.145"></a><a href="lsame.f.html#LSAME.1">LSAME</a>(TRANS,<span class="string">'T'</span>)
NOUNIT = <a name="LSAME.146"></a><a href="lsame.f.html#LSAME.1">LSAME</a>(DIAG,<span class="string">'N'</span>)
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> Set up the start point in X if the increment is not unity. This
</span><span class="comment">*</span><span class="comment"> will be ( N - 1 )*INCX too small for descending loops.
</span><span class="comment">*</span><span class="comment">
</span> IF (INCX.LE.0) THEN
KX = 1 - (N-1)*INCX
ELSE IF (INCX.NE.1) THEN
KX = 1
END IF
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> Start the operations. In this version the elements of AP are
</span><span class="comment">*</span><span class="comment"> accessed sequentially with one pass through AP.
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