private void GenerateDimensionNumbers(int dimension)
{
var di = _directionNumbers.GetInfoForDimension(dimension + 1);
// Read in parameters
var d = (uint)di.Dimension;
var s = di.S;
var a = di.A;
var m = new uint[s + 1];
for (uint i = 1; i <= s; i++)
{
m[i] = di.DirectionNumbers[i - 1];
}
// Compute direction numbers V[1] to V[L], scaled by pow(2,32)
if (_bitsRequired <= s)
{
for (var i = 1; i <= _bitsRequired; i++)
{
_v[dimension][i] = m[i] << (32 - i);
}
}
else
{
for (var i = 1; i <= s; i++)
{
_v[dimension][i] = m[i] << (32 - i);
}
for (var i = s + 1; i <= _bitsRequired; i++)
{
_v[dimension][i] = _v[dimension][i - s] ^ (_v[dimension][i - s] >> (int)s);
for (uint k = 1; k <= s - 1; k++)
{
_v[dimension][i] ^= (((a >> (int)(s - 1 - k)) & 1) * _v[dimension][i - k]);
}
}
}
}
protected void InitDimensions()
{
var nDimensions = _numberOfDimensions + _seed;
//Max number of bits needed
_bitsRequired = (uint)Ceiling(Log(_numberOfPaths + 1.0) / Log(2.0));
//Direction numbers
_v = new uint[nDimensions][];
for (var i = 0; i < (nDimensions); i++)
{
_v[i] = new uint[_bitsRequired];
}
for (var dim = 0; dim < nDimensions; dim++)
{
var v = _v[dim];
//First dim special case
if (dim == 0)
{
for (var i = 0; i < _bitsRequired; i++)
{
v[i] = 1u << (31 - i);
}
}
else
{
var di = _directionNumbers.GetInfoForDimension(dim + 1);
var degree = (int)di.S;
if (_bitsRequired < degree)
{
for (var i = 0; i < _bitsRequired; i++)
{
v[i] = di.DirectionNumbers[i] << (31 - i);
}
}
else
{
for (var i = 0; i < degree; i++)
{
v[i] = di.DirectionNumbers[i] << (31 - i);
}
// The remaining direction numbers are computed as described in
// the Bratley and Fox paper.
// v[i] = a[1]v[i-1] ^ a[2]v[i-2] ^ ... ^ a[v-1]v[i-d+1] ^ v[i-d] ^ v[i-d]/2^d
for (var i = degree; i < _bitsRequired; i++)
{
// First do the v[i-d] ^ v[i-d]/2^d part
v[i] = v[i - degree] ^ (v[i - degree] >> degree);
// Now do the a[1]v[i-1] ^ a[2]v[i-2] ^ ... part
// Note that the coefficients a[] are zero or one and for compactness in
// the input tables they are stored as bits of a single integer. To extract
// the relevant bit we use right shift and mask with 1.
// For example, for a 10 degree polynomial there are ten useful bits in a,
// so to get a[2] we need to right shift 7 times (to get the 8th bit into
// the LSB) and then mask with 1.
for (var j = 1; j < degree; j++)
{
v[i] ^= ((((uint)di.A >> (int)(degree - 1u - j)) & 1) * v[i - j]);
}
}
}
}
}
}