Groovy concurrency
groovy, multithreading
Solution
ok, 2 things:
Inside of the thread's implicit run() method, you are referencing the 'i' variable. I'd have to step it through a debugger to see exactly what happens, but technically, you shouldn't even have access to 'i' there, because it's not final. So, I'd suggest creating a Runnable object to which you pass 'i' in the constructor. Then start the runnable on the thread.
Groovy has great concurrency support - no reason to roll your own like this. Take a look at GPars
Problem
I have a question to Groovy threads. My task is to translate each file in a given directory in a certain manner and place the resulting output in a file in an other directory. I wrote the following code, which works: ``` static def translateDir(fromDir, targetDir) { def allFiles = new File(fromDir).listFiles() def numFiles = allFiles.length for (i in 0..(numFiles - 1)) translate(allFiles[i].getAbsolutePath(), targetDir) } ``` Now, I tried to parallelize this code like this: ``` static def translateDir(fromDir, targetDir) { def allFiles = new File(fromDir).listFiles() def numFiles = allFiles.length def numCores = Runtime.getRuntime().availableProcessors() for (i in 0..(numCores - 1)) { println("Thread " + i + "starting") Thread.start { for (def j = i; j < numFiles; j += numCores) { println("j = " + j) translate(allFiles[j].getAbsolutePath(), targetDir) } } } } ``` which does not work and provides the output: ``` Thread 0 starting Thread 1 starting Thread 2 starting Thread 3 starting ``` nunCores is 4, and numFiles is 3 in my test case. What is going on here?