How to find a good saw function for PRNG?
I think this is an effect of the rounding in your implementation or in the histogram.

Let's say your histogram contains 100 columns. Each represents a width of 0.01. The column at 10 shows how many items fall between 9.995 and 10.005. The column at 0 shows how many items fall between -0.005 and 0.005. However, there are no items below 0, so there is nothing between -0.005 and 0. This column will only show halve of the items in the other columns.