Method GenerateTwiddleTable

src/library/generator.stockham.cpp:546–601

		template <Precision PR>
		void GenerateTwiddleTable(const std::vector<size_t> &radices, std::string &twStr)
		{
			const double TWO_PI = -6.283185307179586476925286766559;

			// Make sure the radices vector sums up to N
			size_t sz = 1;
			for(std::vector<size_t>::const_iterator i = radices.begin();
				i != radices.end(); i++)
			{
				sz *= (*i);
			}
			assert(sz == N);

			// Generate the table
			size_t L = 1;
			size_t nt = 0;
			for(std::vector<size_t>::const_iterator i = radices.begin();
				i != radices.end(); i++)
			{
				size_t radix = *i;

				L *= radix;

				// Twiddle factors
				for(size_t k=0; k<(L/radix); k++)
				{
					double theta = TWO_PI * ((double)k)/((double)L);

					for(size_t j=1; j<radix; j++)
					{
						double c = cos(((double)j) * theta);
						double s = sin(((double)j) * theta);

						//if (fabs(c) < 1.0E-12)	c = 0.0;
						//if (fabs(s) < 1.0E-12)	s = 0.0;

						wc[nt]   = c;
						ws[nt++] = s;
					}
				}
			}

			std::string sfx = FloatSuffix<PR>();

			// Stringize the table
			std::stringstream ss;
			ss.imbue(std::locale("C"));
			ss.precision(34);
			for(size_t i = 0; i < (N-1); i++)
			{
				ss << "("; ss << RegBaseType<PR>(2); ss << ")(";
				ss << std::scientific << wc[i] << sfx << ", ";
				ss << std::scientific << ws[i] << sfx << "),\n";
			}
			twStr += ss.str();
		}
    };