Generic Constraint for max Value of Unpacked Array element

SystemVerilog
,
1

I have following code ::


 class bad_sum1 ;

  rand bit [7:0] b[] ;
  rand bit [7:0] max ;
 
  randc int size_randc ;

  constraint SUM { b.sum() with ( 10'( item ) )  < 1024 ; }  

  constraint SIZE { b.size() == size_randc ; }

  constraint RANDC { size_randc inside { [1:8] } ; }
  
  
  constraint MAX_VALUE {   
                         ( 1023 / ( size_randc ) ) == max ;  // Any issue here ? 
		       }				


  constraint ELEMENT { 
                            foreach( b[i] ) 
			 {
                             b[i] == max ; // [A]
		         }

	             }		  
                                 
                       
  function void post_randomize() ;

     $display("b.sum() is %0d", (b.sum() with ( 10'( item ) ) ) ) ;
     
	 $display("b is %0p",b );

  endfunction

 endclass

 bad_sum1 bs ;

 initial begin

   bs = new();

   repeat(7) // Since size() is 1-7 !!

  if ( bs.randomize() )
    begin
       $display("==========================") ;
    end
  else 
    begin
       $display("Fails") ;
    end


    $display("%0d",int'(1023/5));
    $display("%0d",int'(1023/6));


 end

[Q1] Is the Constraint correct ? I observe that on certain Simulators Constraint Failure occurs and I success only when size is 4/5/6/7 .

Is there any discrepancy with Constraint :: ( 1023 / ( size_randc ) ) == max ?

If the real value ( of 1023 / size_randc ) is X.5 OR X.6 will max be constrained to ( X+1 ) OR X ?

Also ( 1023 / 5 ) has real value of 204.6 so shouldn’t Output be rounded off to 205 ?
Similarly I expected ( 1023 / 6 ) to give 171 rounded off value .

2

In reply to Have_A_Doubt:

Integer division truncates. There is no fractional piece to be rounded.

Regarding the failure, this is an open issue in the LRM:

The semantics of random-cyclical variables requires that they be solved before other random variables. A set of constraints that includes both rand and randc variables shall be solved so that the randc variables are solved first, and this can sometimes cause randomize() to fail.

See 04680: Order of solving randc variables needs to explain how that can cause randomize() to fail - Accellera Mantis