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ctftri.f(3)				      LAPACK				      ctftri.f(3)

NAME
       ctftri.f -

SYNOPSIS
   Functions/Subroutines
       subroutine ctftri (TRANSR, UPLO, DIAG, N, A, INFO)
	   CTFTRI

Function/Subroutine Documentation
   subroutine ctftri (characterTRANSR, characterUPLO, characterDIAG, integerN, complex,
       dimension( 0: * )A, integerINFO)
       CTFTRI

       Purpose:

	    CTFTRI computes the inverse of a triangular matrix A stored in RFP
	    format.

	    This is a Level 3 BLAS version of the algorithm.

       Parameters:
	   TRANSR

		     TRANSR is CHARACTER*1
		     = 'N':  The Normal TRANSR of RFP A is stored;
		     = 'C':  The Conjugate-transpose TRANSR of RFP A is stored.

	   UPLO

		     UPLO is CHARACTER*1
		     = 'U':  A is upper triangular;
		     = 'L':  A is lower triangular.

	   DIAG

		     DIAG is CHARACTER*1
		     = 'N':  A is non-unit triangular;
		     = 'U':  A is unit triangular.

	   N

		     N is INTEGER
		     The order of the matrix A.  N >= 0.

	   A

		     A is COMPLEX array, dimension ( N*(N+1)/2 );
		     On entry, the triangular matrix A in RFP format. RFP format
		     is described by TRANSR, UPLO, and N as follows: If TRANSR =
		     'N' then RFP A is (0:N,0:k-1) when N is even; k=N/2. RFP A is
		     (0:N-1,0:k) when N is odd; k=N/2. IF TRANSR = 'C' then RFP is
		     the Conjugate-transpose of RFP A as defined when
		     TRANSR = 'N'. The contents of RFP A are defined by UPLO as
		     follows: If UPLO = 'U' the RFP A contains the nt elements of
		     upper packed A; If UPLO = 'L' the RFP A contains the nt
		     elements of lower packed A. The LDA of RFP A is (N+1)/2 when
		     TRANSR = 'C'. When TRANSR is 'N' the LDA is N+1 when N is
		     even and N is odd. See the Note below for more details.

		     On exit, the (triangular) inverse of the original matrix, in
		     the same storage format.

	   INFO

		     INFO is INTEGER
		     = 0: successful exit
		     < 0: if INFO = -i, the i-th argument had an illegal value
		     > 0: if INFO = i, A(i,i) is exactly zero.	The triangular
			  matrix is singular and its inverse can not be computed.

       Author:
	   Univ. of Tennessee

	   Univ. of California Berkeley

	   Univ. of Colorado Denver

	   NAG Ltd.

       Date:
	   November 2011

       Further Details:

	     We first consider Standard Packed Format when N is even.
	     We give an example where N = 6.

		 AP is Upper		 AP is Lower

	      00 01 02 03 04 05       00
		 11 12 13 14 15       10 11
		    22 23 24 25       20 21 22
		       33 34 35       30 31 32 33
			  44 45       40 41 42 43 44
			     55       50 51 52 53 54 55

	     Let TRANSR = 'N'. RFP holds AP as follows:
	     For UPLO = 'U' the upper trapezoid A(0:5,0:2) consists of the last
	     three columns of AP upper. The lower triangle A(4:6,0:2) consists of
	     conjugate-transpose of the first three columns of AP upper.
	     For UPLO = 'L' the lower trapezoid A(1:6,0:2) consists of the first
	     three columns of AP lower. The upper triangle A(0:2,0:2) consists of
	     conjugate-transpose of the last three columns of AP lower.
	     To denote conjugate we place -- above the element. This covers the
	     case N even and TRANSR = 'N'.

		    RFP A		    RFP A

					   -- -- --
		   03 04 05		   33 43 53
					      -- --
		   13 14 15		   00 44 54
						 --
		   23 24 25		   10 11 55

		   33 34 35		   20 21 22
		   --
		   00 44 45		   30 31 32
		   -- --
		   01 11 55		   40 41 42
		   -- -- --
		   02 12 22		   50 51 52

	     Now let TRANSR = 'C'. RFP A in both UPLO cases is just the conjugate-
	     transpose of RFP A above. One therefore gets:

		      RFP A		      RFP A

		-- -- -- --		   -- -- -- -- -- --
		03 13 23 33 00 01 02	33 00 10 20 30 40 50
		-- -- -- -- --		      -- -- -- -- --
		04 14 24 34 44 11 12	43 44 11 21 31 41 51
		-- -- -- -- -- --		 -- -- -- --
		05 15 25 35 45 55 22	53 54 55 22 32 42 52

	     We next  consider Standard Packed Format when N is odd.
	     We give an example where N = 5.

		AP is Upper		    AP is Lower

	      00 01 02 03 04		  00
		 11 12 13 14		  10 11
		    22 23 24		  20 21 22
		       33 34		  30 31 32 33
			  44		  40 41 42 43 44

	     Let TRANSR = 'N'. RFP holds AP as follows:
	     For UPLO = 'U' the upper trapezoid A(0:4,0:2) consists of the last
	     three columns of AP upper. The lower triangle A(3:4,0:1) consists of
	     conjugate-transpose of the first two   columns of AP upper.
	     For UPLO = 'L' the lower trapezoid A(0:4,0:2) consists of the first
	     three columns of AP lower. The upper triangle A(0:1,1:2) consists of
	     conjugate-transpose of the last two   columns of AP lower.
	     To denote conjugate we place -- above the element. This covers the
	     case N odd  and TRANSR = 'N'.

		    RFP A		    RFP A

					      -- --
		   02 03 04		   00 33 43
						 --
		   12 13 14		   10 11 44

		   22 23 24		   20 21 22
		   --
		   00 33 34		   30 31 32
		   -- --
		   01 11 44		   40 41 42

	     Now let TRANSR = 'C'. RFP A in both UPLO cases is just the conjugate-
	     transpose of RFP A above. One therefore gets:

		      RFP A		      RFP A

		-- -- --		   -- -- -- -- -- --
		02 12 22 00 01		   00 10 20 30 40 50
		-- -- -- --		      -- -- -- -- --
		03 13 23 33 11		   33 11 21 31 41 51
		-- -- -- -- --			 -- -- -- --
		04 14 24 34 44		   43 44 22 32 42 52

       Definition at line 222 of file ctftri.f.

Author
       Generated automatically by Doxygen for LAPACK from the source code.

Version 3.4.2				 Tue Sep 25 2012			      ctftri.f(3)
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