double[] arr1, arr2, arr3, arr4;
var task1 = Task.Factory.StartNew(() =>
{
arr1 = new double[0];//вызов функции
});
var task2 = Task.Factory.StartNew(() =>
{
arr2 = new double[0];//вызов функции
});
var task3 = Task.Factory.StartNew(() =>
{
arr3 = new double[0];//вызов функции
});
var task4 = Task.Factory.StartNew(() =>
{
arr4 = new double[0];//вызов функции
});
Task.WaitAll(task1, task2, task3, task4);