robot36/utils/radix2.c

/*
Copyright 2015 Ahmet Inan <xdsopl@googlemail.com>

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
 */

#include <math.h>
#include <complex.h>
#include <stdio.h>

int main()
{
	const int N = 512;
	const int dir = -1;
	printf("/* code generated by 'utils/radix2.c' */\n");
	printf("static const int radix2_N = %d;\n", N);
	printf("static const complex_t radix2_z[%d] = {\n", N / 2);
	for (int n = 0; n < N / 2; n++) {
		complex double z = cexp(dir * I * n * 2.0 * M_PI / N);
		printf("\t{ %a, %a }%s\n", creal(z), cimag(z), n < (N/2-1) ? "," : "");
	}
	printf("};\n");
	printf("static inline void dit4(complex_t *out, float *in)\n{\n");
	printf("\tfwd4(out, out + 1, out + 2, out + 3, in[0], in[%i], in[%i], in[%i]);\n}\n", N / 4, N / 2, 3 * N / 4);
	for (int n = 4, s = N / 8; n < N; n *= 2, s /= 2) {
		printf("static void ");
		if (n < N / 2)
			printf("dit%i", n * 2);
		else
			printf("forward");
		printf("(complex_t *out, float *in)\n{\n");
		printf("\tdit%i(out, in);\n", n);
		printf("\tdit%i(out + %i, in + %i);\n", n, n, s);
		printf("\tfor (int k0 = 0, k1 = %i, l1 = 0; k0 < %i; ++k0, ++k1, l1 += %i)\n", n, n, s);
		printf("\t\tdft2(out + k0, out + k1, out[k0], cmul(radix2_z[l1], out[k1]));\n");
		printf("}\n");
	}
	return 0;
}