spftrs.f(3) [centos man page]

```spftrs.f(3)							      LAPACK							       spftrs.f(3)

NAME
spftrs.f -

SYNOPSIS
Functions/Subroutines
subroutine spftrs (TRANSR, UPLO, N, NRHS, A, B, LDB, INFO)
SPFTRS

Function/Subroutine Documentation
subroutine spftrs (characterTRANSR, characterUPLO, integerN, integerNRHS, real, dimension( 0: * )A, real, dimension( ldb, * )B, integerLDB,
integerINFO)
SPFTRS

Purpose:

SPFTRS solves a system of linear equations A*X = B with a symmetric
positive definite matrix A using the Cholesky factorization
A = U**T*U or A = L*L**T computed by SPFTRF.

Parameters:
TRANSR

TRANSR is CHARACTER*1
= 'N':  The Normal TRANSR of RFP A is stored;
= 'T':  The 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.

NRHS

NRHS is INTEGER
The number of right hand sides, i.e., the number of columns
of the matrix B.  NRHS >= 0.

A

A is REAL array, dimension ( N*(N+1)/2 )
The triangular factor U or L from the Cholesky factorization
of RFP A = U**H*U or RFP A = L*L**T, as computed by SPFTRF.
See note below for more details about RFP A.

B

B is REAL array, dimension (LDB,NRHS)
On entry, the right hand side matrix B.
On exit, the solution matrix X.

LDB

LDB is INTEGER
The leading dimension of the array B.  LDB >= max(1,N).

INFO

INFO is INTEGER
= 0:  successful exit
< 0:  if INFO = -i, the i-th argument had an illegal value

Author:
Univ. of Tennessee

Univ. of California Berkeley

NAG Ltd.

Date:
November 2011

Further Details:

We first consider Rectangular Full Packed (RFP) 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
the 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
the transpose of the last three columns of AP lower.
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 = 'T'. RFP A in both UPLO cases is just the
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 then consider Rectangular Full Packed (RFP) 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
the 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
the transpose of the last two columns of AP lower.
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 = 'T'. RFP A in both UPLO cases is just the
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 200 of file spftrs.f.

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