-- File:	Householder.cdl
-- Created:	Wed Aug  7 10:24:48 1991
-- Author:	Laurent PAINNOT
--		<lpa@topsn3>
---Copyright:	 Matra Datavision 1991, 1992



class Householder from math

    	---Purpose: This class implements the least square solution of a set of
    	--          linear equations of m unknowns (n >= m) using the Householder
    	--          method. It solves A.X = B.
    	--          This algorithm has more numerical stability than 
    	--          GaussLeastSquare but is longer.
    	--          It must be used if the matrix is singular or nearly singular.
    	--          It is about 16% longer than GaussLeastSquare if there is only
    	--          one member B to solve.
    	--          It is about 30% longer if there are twenty B members to solve.

uses Matrix from math,
     Vector from math,
     OStream from Standard

raises NotDone from StdFail,
       OutOfRange from Standard,
       DimensionError from Standard,
       ConstructionError from Standard

is

    Create(A, B: Matrix; EPS: Real = 1.0e-20)
    	---Purpose: Given an input matrix A with n>= m, given an input matrix B
    	--          this constructor performs the least square resolution of 
    	--          the set of linear equations A.X = B for each column of B.
    	--          If a column norm is less than EPS, the resolution can't 
    	--          be done.
    	--          Exception DimensionError is raised if the row number of B
    	--          is different from the A row number.

    returns Householder
    raises DimensionError;

    Create(A, B: Matrix; lowerArow, upperArow, lowerAcol, upperAcol: Integer;
           EPS: Real = 1.0e-20)
    	---Purpose: Given an input matrix A with n>= m, given an input matrix B
    	--          this constructor performs the least square resolution of 
    	--          the set of linear equations A.X = B for each column of B.
    	--          If a column norm is less than EPS, the resolution can't 
    	--          be done.
    	--          Exception DimensionError is raised if the row number of B
    	--          is different from the A row number.

    returns Householder
    raises DimensionError;


    Create(A: Matrix; B: Vector; EPS: Real = 1.0e-20)
    	---Purpose: Given an input matrix A with n>= m, given an input vector B
    	--          this constructor performs the least square resolution of 
    	--          the set of linear equations A.X = B.
    	--          If a column norm is less than EPS, the resolution can't 
    	--          be done.
    	--          Exception DimensionError is raised if the length of B
    	--          is different from the A row number.

    returns Householder
    raises DimensionError;


    Perform(me: in out; A, B: Matrix; EPS: Real) 
    	---Purpose: This method is used internally for each constructor 
    	--          above and can't be used directly. 

    is static protected;


    IsDone(me)
    	---Purpose: Returns true if the computations are successful, otherwise returns false.
    	---C++: inline
    returns Boolean
    is static;
    
    
    Value(me; sol : out Vector; Index: Integer = 1)
    	---Purpose: Given the integer Index, this routine returns the 
    	--          corresponding least square solution sol.
    	--          Exception NotDone is raised if the resolution has not be 
    	--          done.
    	--          Exception OutOfRange is raised if Index <=0 or 
    	--          Index is more than the number of columns of B.
    	---C++: inline

    raises NotDone, OutOfRange
    is static;


    AllValues(me)
    	---Purpose: Returns the matrix sol of all the solutions of the system 
    	--          A.X = B.
    	--          Exception NotDone is raised is the resolution has not be 
    	--          done.
    	---C++: inline
    	---C++: return const&

    returns Matrix	    
    raises NotDone, ConstructionError
    is static;
    

    
    Dump(me; o: in out OStream)
    	---Purpose: Prints informations on the current state of the object.

    is static;


fields

Sol:         Matrix;
Q:           Matrix;
Done:        Boolean;
mylowerArow: Integer;
myupperArow: Integer;
mylowerAcol: Integer;
myupperAcol: Integer;

end Householder;