Compile-time generated 2D array in D - multidimensional-array

Question

In my program I need to generate array with powers' (from 0 to 5) sum of numbers from 1 to 100,000.
So I tried to compile this code:
const enum size_t MAX_ARRAY_SIZE = 100_000 + 1;
const enum size_t MAX_POWER_SIZE = 5 + 1;
const enum power_sum = calc_power_sum();
// some unimportant code here
pure ulong[MAX_POWER_SIZE][MAX_ARRAY_SIZE] calc_power_sum() {
ulong[MAX_POWER_SIZE][MAX_ARRAY_SIZE] power_sum;
power_sum[0][] = 1;
foreach (x, ref element; power_sum[1]) {
element = x;
}
foreach (n; 2 .. MAX_POWER_SIZE) {
foreach (x, ref element; power_sum[n]) {
element = power_sum[n - 1][x] * power_sum[1][x];
}
}
foreach (ref power; power_sum) {
foreach (x; 1 .. MAX_ARRAY_SIZE) {
power[x] += power[x - 1]; // error appears here
}
}
return power_sum;
}
But compiler says:
$ dmd problem.d
problem.d(130): Error: array index 6 is out of bounds [1LU, 2LU, 3LU, 4LU, 5LU, 6LU][0 .. 6]
problem.d(15): called from here: calc_power_sum()
What am I doing wrong?

Answer 1

At first glance looks like you have simply misunderstood array dimension order. You have
ulong[MAX_POWER_SIZE][MAX_ARRAY_SIZE]
and your code assumes directly opposite
ulong[MAX_ARRAY_SIZE][MAX_POWER_SIZE]
Also I am afraid 100 000 may be a bit too much, after above mentioned fix I get an internal compiler error. Works for smaller MAX_ARRAY_SIZE values though.

Answer 2

As Mihail said, you should reverse the order of dimensions.
However, you most likely won't be able to do what you plan for all sizes because the maximum size of static array is limited in D ( http://dlang.org/arrays.html ) :
The total size of a static array cannot exceed 16Mb.