/* Skandium: A Java(TM) based parallel skeleton library.
*
* Copyright (C) 2009 NIC Labs, Universidad de Chile.
*
* Skandium is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* Skandium is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
* You should have received a copy of the GNU General Public License
* along with Skandium. If not, see <http://www.gnu.org/licenses/>.
*/
package cl.niclabs.skandium.system;
import java.util.ArrayList;
import java.util.List;
import java.util.Stack;
import java.util.concurrent.ExecutionException;
import cl.niclabs.skandium.instructions.Instruction;
import cl.niclabs.skandium.skeletons.AbstractSkeleton;
import cl.niclabs.skandium.skeletons.Skeleton;
import cl.niclabs.skandium.system.Task;
/**
* The interpretation code.
*
* @author mleyton
*/
public class Interpreter {
/**
* This is the main interpretation method.
*
* The method pops instructions from the computation stack, and executes them with the data parameter.
* The data parameter is then updated with the result of the execution. The process is looped until, either
* the stack is empty or children stacks are generated (data parallelism).
*
* In the later case, each child stack is encapsulated along with its data parameter
* into a child {@link Task} object, and submitted for execution.
*
* If an exception is raised during the computation of an instruction, the {@link Task} is notified
* with the exception.
*
* @param task The source of the stack and parameter to compute.
* @return The task holding the current state of the computation (usually the same as the input)
*/
static Task interpret(Task task){
//get the current data, stack and strace
Object P = task.getP();
Stack<Instruction> stack = task.getStack();
@SuppressWarnings("rawtypes")
Skeleton[] strace = null;
try{
//array for storing children if needed
List<Stack<Instruction>> children = new ArrayList<Stack<Instruction>>();
//iterate while there are instructions and no children tasks
while(!stack.empty() && children.size() <= 0){
//pop the instruction and interpret it
Instruction inst = stack.pop();
strace= inst.getSkeletonTrace(); //skeleton trace in case of exception
P = inst.interpret(P, stack, children);
//check that the task has not been canceled
if(task.isCancelled()) return task;
}
//update the task with the latest data
task.setP(P);
//Data parallelism has been reached
if(children.size() > 0){
task.setP(null); //free memory parent not needed any more
task.setStack(stack); //store the stack to merge results later
Object[] Ps = (Object[])P;
if(children.size() != Ps.length){
throw new Exception("Data parallelism error. Substacks size is different than parameter length.");
}
synchronized(task){
//add children tasks
for(int i=0; i < Ps.length; i++){
task.addChild(Ps[i], children.get(i));
}
//schedule children for execution
task.sendChildrenToExecution();
}
return task;
}
}
catch(Throwable t){
setLogicalException(t, strace);
//if exception was raised we send it back to the user
task.setException(new ExecutionException(t));
}
return task;
}
@SuppressWarnings("rawtypes")
private static void setLogicalException(Throwable t, Skeleton[] strace){
ArrayList<StackTraceElement> list = new ArrayList<StackTraceElement>();
//iterate over every trace
for(int i=0;i<t.getStackTrace().length;i++){
String className = t.getStackTrace()[i].getClassName();
Class cls;
try {
cls = Class.forName(className);
} catch (ClassNotFoundException e) {
list.add(t.getStackTrace()[i]);
continue;
}
/* If the trace belongs to an instruction then we replace it.
* We also double check that the "next" trace corresponds to Interperter.
*
* i+1:cl.niclabs.skandium.system.Interpreter.interpret(Interpreter.java:68)
* i:cl.niclabs.skandium.instructions.DaCInst.interpret(DaCInst.java:71) */
if( Instruction.class.isAssignableFrom(cls) &&
t.getStackTrace()[i+1].getClassName().equals(Interpreter.class.getCanonicalName())){
for(int j=strace.length-1; j>=0; j--){
list.add(((AbstractSkeleton)strace[j]).getTrace());
}
}
else{
list.add(t.getStackTrace()[i]);
}
}
t.setStackTrace(list.toArray(new StackTraceElement[list.size()]));
}
}