list - Groovy built-in to split an array into equal sized subarrays? - Stack Overflow
def partition(array, size) {
def partitions = []
int partitionCount = array.size() / size
partitionCount.times { partitionNumber ->
def start = partitionNumber * size
def end = start + size - 1
partitions << array[start..end]
}
if (array.size() % size) partitions << array[partitionCount * size..-1]
return partitions
}