OutOfMemoryError using JEP

[LUIS ALBERTO RIVERA RIERA]

Hi,

This is Luis, I am working for a Credit Card company and we are using your demo product(Jep java) to evaluate client’s scores and actually we are in a Test stage but we are facing java.lang.OutOfMemoryError problems when we are running a set of 25000 clients.

The application consist in a RPG program that call a Evaluate.jar where we have implemented the logic to evaluate expressions. 

All the clients have 200 expression to evaluate so finally we have a loop for a total = 50000000 repetitions( 25000clients*200expression = 50000000 ).

The count loop reached = 245000 and we got java.lang.OutOfMemoryError.

I would like that you guys can give support with this problem.

This is the code that i am using :

package ec.com.diners.evaluator;

import java.text.DecimalFormat;

import java.util.Locale;

import org.slf4j.Logger;

import org.slf4j.LoggerFactory;

import com.singularsys.jep.Jep;

import com.singularsys.jep.ParseException;

import com.singularsys.jep.configurableparser.StandardConfigurableParser;

public abstract class WrapperEvaluator{

public static String verifyExpression(String expression) throws Exception{

try{

       Jep jep = new Jep(new StandardConfigurableParser());

String[] parms = expression.split("#");

String formula = parms[0];

formula.intern();

for (int i = 1; i < parms.length; i++) {

       if (parms[i] != null) {

           String[] paramList = parms[i].split("=");

           String nombreVariable = paramList[0];

           nombreVariable.intern();

           String valorVariable = paramList[1];

           if(valorVariable.length() > 14){

  char indicadorNegativo; 

  String parteEntera  =  valorVariable.substring(0,9);

  String parteDecimal = valorVariable.substring(9,15);

  indicadorNegativo = parteDecimal.charAt(5);

  if(!Character.isDigit(indicadorNegativo)){

parteDecimal = valorVariable.substring(9,14);

jep.addVariable(nombreVariable,Double.parseDouble(parteEntera+"."+parteDecimal)*-1);

}else

jep.addVariable(nombreVariable,Double.parseDouble(parteEntera+"."+parteDecimal));

}

}

}

   jep.parse(formula);

Object var = jep.evaluate(); 

Locale.setDefault(Locale.US);

   DecimalFormat num = new DecimalFormat("#########.000000");

   jep=null;    

   return num.format(var);

}

catch( ParseException ex){

Logger logger = LoggerFactory.getLogger(WrapperEvaluator.class);

logger.error(ex.getStackTrace().toString());

return ex.getMessage();

}

finally{

Logger logger = LoggerFactory.getLogger(WrapperEvaluator.class);

StringBuffer message = new StringBuffer(100);

long heapMaxSize = Runtime.getRuntime().maxMemory();

long heapSize = Runtime.getRuntime().totalMemory();

long heapFreeSize = Runtime.getRuntime().freeMemory();

message.append(" RESUMEN **** HeapMaxSize: " + heapMaxSize + " HeapSize: " + heapSize + " HeapFreeSize :" + heapFreeSize);

logger.debug(message.toString());

if(heapSize == heapMaxSize){

System.gc();

logger.debug("Llamando al GC: Actual heapFreeSize: "+ heapFreeSize);

}

}

}

}

Thanks in advance.

[Richard Morris]

Hi Luis,

Thats quite a nice test for the system, one of the largest I've seen. A few thoughts.

You are creating a new Jep instance each time verifyExpression() is called. This takes some memory and time it will be better to reuse the same Jep instance. So change

public abstract class WrapperEvaluator{

public static String verifyExpression(String expression) throws Exception{

try{

        Jep jep = new Jep(new StandardConfigurableParser());

                ...

                }

        }

 }

to

public abstract class WrapperEvaluator{

Jep jep = new Jep(new StandardConfigurableParser());

public static String verifyExpression(String expression) throws Exception{

try{

                ...

                }

        }

 }

Keeping the same jep instance has some implications, mainly the variables will be kept. You may want to call

       jep.getVariableTable().clear();

or

        jep.getVariableTable().remove("x");

The other thing I note is the use of String.intern. I don't know much about this method but reading 

http://stackoverflow.com/questions/1091045/is-it-good-practice-to-use-java-lang-string-intern 

seems to indicate problems with garbage collection.

Further investigation might involve static memory analysis to see which classes are using up the space. Some sample expressions might help.

Richard