# cpftrf.f(3) [centos man page]

```cpftrf.f(3)							      LAPACK							       cpftrf.f(3)

NAME
cpftrf.f -

SYNOPSIS
Functions/Subroutines
subroutine cpftrf (TRANSR, UPLO, N, A, INFO)
CPFTRF

Function/Subroutine Documentation
subroutine cpftrf (characterTRANSR, characterUPLO, integerN, complex, dimension( 0: * )A, integerINFO)
CPFTRF

Purpose:

CPFTRF computes the Cholesky factorization of a complex Hermitian
positive definite matrix A.

The factorization has the form
A = U**H * U,  if UPLO = 'U', or
A = L  * L**H,  if UPLO = 'L',
where U is an upper triangular matrix and L is lower triangular.

This is the block version of the algorithm, calling Level 3 BLAS.

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':  Upper triangle of RFP A is stored;
= 'L':  Lower triangle of RFP A is stored.

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 Hermitian 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 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, if INFO = 0, the factor U or L from the Cholesky
factorization RFP A = U**H*U or RFP A = L*L**H.

INFO

INFO is INTEGER
= 0:  successful exit
< 0:  if INFO = -i, the i-th argument had an illegal value
> 0:  if INFO = i, the leading minor of order i is not
positive definite, and the factorization could not be
completed.

Further Notes on RFP Format:
============================

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

Author:
Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Date:
November 2011

Definition at line 212 of file cpftrf.f.

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

Version 3.4.2							  Tue Sep 25 2012						       cpftrf.f(3)```
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