I would think that incremental adding a smaller portion of the sugars would be beneficial. Here's why:
Adding a large amount of sugar at once to a actively fermenting brew will cause a majority of the sugar to drop to the bottom of your fermenter. This dense sugar sludge at the bottom is too highly concentrated for yeast to ferment.
If you have already dumped the sugar in, I would swirl the fermenter for a few days to swirl up the sugars.
Just my thoughts,
Fermenting: Oud Bruin, American Brown, Ginger Mead
Bottled: Super RIS, Imperial Stout, Raspberry&Blueberry Mead, Belgian Strong Ale, Oak Aged Rye Barley Wine
Kegged: APA, Schwarz Braggot, Irish Red, Berliner Weisse
Gallons Brewed in 2012: 76