Algorithm used for PLA_Chol:

  ******************************************************************
      
      Partition  A = / A_TL ||   *  \
                     | =====  ===== |
                     \ A_BL || A_BR /
     	     where A_TL is 0 x 0 
      while A_BR is not 0 x 0 
         Determine block size b
	 Partition  A = / A_TL ||   *  \    / A_00 ||  *   |  *   \ 
                        | =====  ===== | =  | ====    ====   ==== |
                        \ A_BL || A_BR /    | A_10 || A_11 |  *   |
                                            | ----    ----   ---- |
                                            \ A_20 || A_21 | A_22 /
     	        where A_00 = A_TL and A_11 is b x b 
         Update A_11 <- L_11 = Chol. Fact.( A_11 )
         Update A_21 <- L_21 = A_21 inv( L_11' )
	 Update A_22 <- A_22 - L_21 * L_21'
         Continue with
	            A = / A_TL ||   *  \    / A_00 |  *   ||  *   \ 
                        | =====  ===== | =  | ----   ----    ---- |
                        \ A_BL || A_BR /    | A_10 | A_11 ||  *   |
                                            | ====   ====    ==== |
                                            \ A_20 | A_21 || A_22 /
      endwhile
              
  ******************************************************************