Root class TDecompQRH  how to use 
The question is actually: How to ubderstand a completely misleading description of the class?
The question has been raised in RootTalk  TDecompQRH  how to use the householder decomposition?  but was not answered properly by the author, Eddy Offermann .
Here is a snpashot of the description from the Root User's Guide v5.26:
Having inspected the code, I found that the code may be ok, but the description is wrong and requires the following corrections line by line:
original  comment / corrected version 

Decompose an (m x n)matrix A with m ≥ n.  ok 
A = QRH  A = QR

Q : orthogonal (m x n)  matrix, stored in fQ;  Everything wrong! "Orthogonal"  yes, but :
can be expessed via as where That allows the matrix Q to be stored implicitly via a set of (in fQ and fUp, see below) and  for faster computations in future  a set of (in fW). Now we can describe what does fQ contain?

R : upper triangular (n x n)matrix, stored in fR;  It is found as , calculated iteratively: (to be noted: ) First, R is computed and placed into upper part of fQ, then copied into fR 
H : (n x n)Householder matrix, stored through;  The H matrix is a nonsence: as we see, the involved matrices are of dimension (m x m), and the Householder matrices of dimensions (m x m), (m1 x m1), ... . 
fUp : nvector with Householder up‘s;  Correct if one deciphers the "Householder up‘s" as upper components of Householder vectors , i.e. 
fW : nvector with Householder beta‘s.  Similarly, an explicit definition is much better: 
The decomposition fails if in the formation of reflectors a zero appears, i.e. singularity.  ? (I did not check this statement) 
I  Attachment  History  Action  Size  Date  Who  Comment 

djvu  Golub_VanLoan.Matr_comp_2ed_ru.djvu  r1  manage  7867.5 K  20110502  04:37  AlexanderFedotov  
Golub_VanLoan.Matr_comp_3ed.pdf  r1  manage  11833.8 K  20110502  04:25  AlexanderFedotov  
gif  QRH_userguide526.gif  r1  manage  15.3 K  20110503  20:05  AlexanderFedotov 
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