JNI performance

Question

I have a problem with JNI performance. The following simple array manipulation takes twice longer using JNI than pure Java. The dll is compiled under VC++ 4.0. Am I doing something wrong or JNI simply puts out too much overhead when calling C dll?
JNIEXPORT void JNICALL
Java_VisualEffect_zoomR(JNIEnv *env, jobject obj,  jint len,jdoubleArray arr, jintArray arr1, jintArray arr2)
     jint *carr1, *carr2;
     jdouble *rnd;
     jint i;
     carr1=(*env)->GetIntArrayElements(env, arr1, NULL);
     carr2=(*env)->GetIntArrayElements(env, arr2, NULL);
     rnd=(*env)->GetDoubleArrayElements(env, arr, NULL);
     if ( carr1==NULL|| carr2==NULL )
          return 0;
     if ( rnd==NULL )
          return 0;
     for(i=0; i<len; i++)
          carr1= carr2[i]*rnd[i];
(*env)->ReleaseIntArrayElements(env, arr1, carr1,0);
     (*env)->ReleaseIntArrayElements(env, arr2, carr2,0);
     (*env)->ReleaseDoubleArrayElements(env, arr, rnd,0);
Appreciate any suggestions.
Jay

Answer 1

It may also simply be that Java is actually faster than C in this trivial case or there is no difference and so the overhead matters. How big are these arrays?