How to specify for JVM the stack for ONE specific thread that invokes JNI

Question

Hello all!
I'm 2 days now looking for a solution in several forums but even in Sun Java Forums nobody was able to come up with a solution. If you know a better forum to place it, please let me know.
Description:
I have an application that launches several threads of different types. One of them is quite specific and run a critical JNI C++ process. The remaining ones are just for controling of other stuff... When I call the application by the command line
java -classpath ... -Xss20m -Djava.library.path ... pack.subpack.myApp
the application usually crashes: My computer has 256MB RAM of memory that vanish in seconds and causes an OutOfMemoryException
Sometimes the application works properly, but sometimes the memory usage goes up fast until a general crash.
What I believe that is going on:
When we declare -Xss20m, I undestand that for each thread the JVM will attemp to allocate more 20MB, and if I have 10 threads, it goes up to 200MB and so on; however I'd like to have 20MB just for my critical process (that is called in one specific thread) and not for any thread.
If I try to reduce -Xss parameter to, let's say 10MB, my C++ process overflow the JVM stack for the thread.
So, does any body have know how to solve it? Please... I need experts help!
Thanks a lot,
Calegari

Answer 1

There we go...
I have this class:
package calegari.automata;
* <p>Title: </p>
* <p>Description: </p>
* <p>Copyright: Copyright (c) 2003</p>
* <p>Company: </p>
* @author Aur�lio Calegari
* @version 1.0
public class Native {
* Parameters:
* individuals --> All binary individual (AC rule)
* indivLength --> number of infividuals
* numEval --> number of RIs
* generateUniform --> Uniform distribution of density
* seed --> seed for current generation
public native double[] AutomataIterator(int[][] individuals,
int indvLength,
int numEval,
boolean generateUniform,
long seed
static {
System.loadLibrary("Native");
public Native() {
Then, running
javah -classpath ... calegari.automata.Native
I'll get the following .h
/* DO NOT EDIT THIS FILE - it is machine generated */
#include "jni.h"
/* Header for class calegari_automata_Native */
#ifndef Includedcalegari_automata_Native
#define Includedcalegari_automata_Native
#ifdef __cplusplus
extern "C" {
#endif
* Class: calegari_automata_Native
* Method: AutomataIterator
* Signature: ([[IIIZJ)[D
JNIEXPORT jdoubleArray JNICALL
Java_calegari_automata_Native_AutomataIterator___3_3IIIZJ
(JNIEnv *, jobject, jobjectArray, jint, jint, jboolean, jlong);
#ifdef __cplusplus
#endif
#endif
Next, I built my cpp file which is right bellow
#include <stdio.h>
#include <stdlib.h>
#include <conio.h>
#include "jni.h"
#include "calegari_automata_Native.h"
#include "util.h"
double IndividualEvaluator(long rule[], int automataCells[][149], int numInit1s[],
int numOfACs, int numEvaluations);
char getNext(char simb);
JNIEXPORT jdoubleArray JNICALL
Java_calegari_automata_Native_AutomataIterator___3_3IIIZJ
(JNIEnv *env, jobject jobj, jobjectArray indiv, jint length, jint numEval,
     jboolean isUniform, jlong seed)
printf("Native JVM call for C++ critical block: Started \a[-]");
int ACs[10000][149]; //Will be filled with 100000 Initial states of a cellular automata
int numIndiv = length;
int numOfACs = numEval;
//Dencity of each Initial state of cellular automata
int num1sRIs[10000];
//response
double resp[1000];
//set seed
srand((unsigned int) seed);
//generate Cellular automata states
//Uniform generation
if(isUniform)
for(int i=0;i<numEval;i++)
int num1s;
num1s=0;
for(int j=0;j<149;j++)
ACs[i][j] = ((rand()%numEval)<i+1?0:1);
if(ACs[i][j]==1) num1s++;
num1sRIs[i] = num1s;
printf(" %d ",num1s);
else //not uniform generation
for(int i=0;i<numEval;i++)
int num1s;
num1s=0;
for(int j=0;j<149;j++)
ACs[i][j] = rand()%2;
if(ACs[i][j]==1) num1s++;
num1sRIs[i] = num1s;
//load individuals and start the critical method
char simb = '-';
for(int i=0;i<numIndiv;i++)
jintArray oneDim = (jintArray) env->GetObjectArrayElement(indiv, i);
jint *indiv=env->GetIntArrayElements(oneDim, 0);
simb = getNext(simb);
printf("\b\b%c]",simb);
resp[i] = IndividualEvaluator(indiv,ACs,num1sRIs,numOfACs,300);
jdoubleArray retApts;
retApts = env->NewDoubleArray(numIndiv);
env->SetDoubleArrayRegion((jdoubleArray)retApts,(jsize)0,numIndiv,(jdouble *)resp);
printf("\nReturning to Java plataform: Completed\a\a\n");
return retApts;
char getNext(char simb)
if(simb=='-') simb = '\\';
else if(simb=='\\') simb = '|';
else if(simb=='|') simb = '/';
else if(simb=='/') simb = '-';
return simb;
Then it works fine since we declare the size of the stack to JVM, however, if we don't... We get a crash!
Any idea?
Thanks