-- File:        Gauss.cdl
-- Created:     Mon May 13 15:45:42 1991
-- Author:      Laurent PAINNOT
--              <lpa@topsn3>
---Copyright:    Matra Datavision 1991, 1992



class Gauss from math 
    ---Purpose:
    -- This class implements the Gauss LU decomposition (Crout algorithm) 
    -- with partial pivoting (rows interchange) of a square matrix and 
    -- the different possible derived calculation : 
    --    - solution of a set of linear equations.
    --    - inverse of a matrix.
    --    - determinant of a matrix.


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

raises NotSquare from math, 
       DimensionError from Standard,
       NotDone from StdFail

is 

    Create(A: Matrix; MinPivot: Real = 1.0e-20)
    ---Purpose:
    -- Given an input n X n matrix A this constructor performs its LU 
    -- decomposition with partial pivoting (interchange of rows).
    -- This LU decomposition is stored internally and may be used to
    -- do subsequent calculation.
    -- If the largest pivot found is less than MinPivot the matrix A is 
    -- considered as singular.
    -- Exception NotSquare is raised if A is not a square matrix.

    returns Gauss
    raises NotSquare;

    
    
    IsDone(me)
    	---Purpose: Returns true if the computations are successful, otherwise returns false
       	---C++: inline
     returns Boolean
     is static;


    Solve(me; B: Vector; X : out Vector)
    ---Purpose:
    -- Given the input Vector B this routine returns the solution X of the set
    -- of linear equations A . X = B. 
    -- Exception NotDone is raised if the decomposition of A was not done
    -- successfully. 
    -- Exception DimensionError is raised if the range of B is not 
    -- equal to the number of rows of A.
    
    raises NotDone, 
    	   DimensionError
    is static;


    Solve(me; B: in out Vector)
    ---Purpose:
    -- Given the input Vector B this routine solves the set of linear 
    -- equations A . X = B. B is replaced by the vector solution X. 
    -- Exception NotDone is raised if the decomposition of A was not done
    -- successfully.
    -- Exception DimensionError is raised if the range of B is not 
    -- equal to the number of rows of A.

    raises DimensionError
    is static;
    
    
    Determinant(me)
    ---Purpose:
    -- This routine returns the value of the determinant of the previously LU 
    -- decomposed matrix A.
    -- Exception NotDone may be raised if the decomposition of A was not done
    -- successfully, zero is returned if the matrix A was considered as singular.

    returns Real
    raises NotDone
    is static;


    Invert(me; Inv: out Matrix)
    ---Purpose:
    -- This routine outputs Inv the inverse of the previously LU decomposed
    -- matrix A.
    -- Exception DimensionError is raised if the ranges of B are not 
    -- equal to the ranges of A.

    raises DimensionError
    is static;


    Dump(me; o: in out OStream)
    	---Purpose: Prints on the stream o information on the current state 
    	--          of the object.
    	--          Is used to redefine the operator <<.

    is static;


fields

Done:     Boolean;
Singular: Boolean is protected;
LU:       Matrix is protected;
Index:    IntegerVector is protected;
D:        Real is protected;



end Gauss;