Accumulates: min does not work after retracting fact.

rule "rule1_long"
    when
        accumulate( Fact( $longVal: longVal), $minVal : min($longVal))
        accumulate( Fact( $longVal2: longVal, $longVal2 > $minVal), $minVal2 : min($longVal2))

        $minFact: Fact( longVal == $minVal)
        $minFact2: Fact( longVal == $minVal2)

    then
		System.out.println("Rule ["+kcontext.getRule().getName()+ "] fires!");        
		Long $diff = (Long)$minVal2 - (Long)$minVal;
		$minFact2.setDiff($diff);
//		update($minFact2);
 		String errmsg = $diff == 0?  " !!!!! ERROR !!!!!" : "";
		System.out.println( drools.getRule().getName() + " diff：" + $minFact2.getLongVal()  + " - " + $minFact.getLongVal() + " = " + $diff + errmsg);
		System.out.println("\tretract <= "+$minFact );
		retract($minFact);			

end