Functions/Subroutines
subroutine	stpqrt (M, N, L, NB, A, LDA, B, LDB, T, LDT, WORK, INFO)
	STPQRT

Function/Subroutine Documentation

subroutine stpqrt	(	integer	M,
		integer	N,
		integer	L,
		integer	NB,
		real, dimension( lda, * )	A,
		integer	LDA,
		real, dimension( ldb, * )	B,
		integer	LDB,
		real, dimension( ldt, * )	T,
		integer	LDT,
		real, dimension( * )	WORK,
		integer	INFO
	)

STPQRT

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Purpose:

 STPQRT computes a blocked QR factorization of a real 
 "triangular-pentagonal" matrix C, which is composed of a 
 triangular block A and pentagonal block B, using the compact 
 WY representation for Q.

Parameters:

[in]	M	M is INTEGER The number of rows of the matrix B. M >= 0.
[in]	N	N is INTEGER The number of columns of the matrix B, and the order of the triangular matrix A. N >= 0.
[in]	L	L is INTEGER The number of rows of the upper trapezoidal part of B. MIN(M,N) >= L >= 0. See Further Details.
[in]	NB	NB is INTEGER The block size to be used in the blocked QR. N >= NB >= 1.
[in,out]	A	A is REAL array, dimension (LDA,N) On entry, the upper triangular N-by-N matrix A. On exit, the elements on and above the diagonal of the array contain the upper triangular matrix R.
[in]	LDA	LDA is INTEGER The leading dimension of the array A. LDA >= max(1,N).
[in,out]	B	B is REAL array, dimension (LDB,N) On entry, the pentagonal M-by-N matrix B. The first M-L rows are rectangular, and the last L rows are upper trapezoidal. On exit, B contains the pentagonal matrix V. See Further Details.
[in]	LDB	LDB is INTEGER The leading dimension of the array B. LDB >= max(1,M).
[out]	T	T is REAL array, dimension (LDT,N) The upper triangular block reflectors stored in compact form as a sequence of upper triangular blocks. See Further Details.
[in]	LDT	LDT is INTEGER The leading dimension of the array T. LDT >= NB.
[out]	WORK	WORK is REAL array, dimension (NB*N)
[out]	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; Univ. of Colorado Denver; NAG Ltd.

Date:: April 2012

Further Details:

  The input matrix C is a (N+M)-by-N matrix  

               C = [ A ]
                   [ B ]        

  where A is an upper triangular N-by-N matrix, and B is M-by-N pentagonal
  matrix consisting of a (M-L)-by-N rectangular matrix B1 on top of a L-by-N
  upper trapezoidal matrix B2:

               B = [ B1 ]  <- (M-L)-by-N rectangular
                   [ B2 ]  <-     L-by-N upper trapezoidal.

  The upper trapezoidal matrix B2 consists of the first L rows of a
  N-by-N upper triangular matrix, where 0 <= L <= MIN(M,N).  If L=0, 
  B is rectangular M-by-N; if M=L=N, B is upper triangular.  

  The matrix W stores the elementary reflectors H(i) in the i-th column
  below the diagonal (of A) in the (N+M)-by-N input matrix C

               C = [ A ]  <- upper triangular N-by-N
                   [ B ]  <- M-by-N pentagonal

  so that W can be represented as

               W = [ I ]  <- identity, N-by-N
                   [ V ]  <- M-by-N, same form as B.

  Thus, all of information needed for W is contained on exit in B, which
  we call V above.  Note that V has the same form as B; that is, 

               V = [ V1 ] <- (M-L)-by-N rectangular
                   [ V2 ] <-     L-by-N upper trapezoidal.

  The columns of V represent the vectors which define the H(i)'s.  

  The number of blocks is B = ceiling(N/NB), where each
  block is of order NB except for the last block, which is of order 
  IB = N - (B-1)*NB.  For each of the B blocks, a upper triangular block
  reflector factor is computed: T1, T2, ..., TB.  The NB-by-NB (and IB-by-IB 
  for the last block) T's are stored in the NB-by-N matrix T as

               T = [T1 T2 ... TB].

Definition at line 189 of file stpqrt.f.

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