added precalculated twiddles table, fixed accuracy issues (switched from int32 to int64). Now FFT working correctly

C/FP_math.c

@@ -11,10 +11,12 @@
 
 
 
-int cos_delta_FP_arr[DATA_L] = {0,};
+int64_t cos_delta_FP_arr[DATA_L] = {0,};
-int sin_delta_FP_arr[DATA_L] = {0,};
+int64_t sin_delta_FP_arr[DATA_L] = {0,};
+int64_t wr_arr[DATA_L][DATA_L / 2] = {0,};
+int64_t wi_arr[DATA_L][DATA_L / 2] = {0,};
 
-void FFT_fp(uint32_t* inp, uint32_t inp_L, uint32_t* buf){
+void FFT_fp(int64_t* inp, uint32_t inp_L, int64_t* buf){
 
 	    // buf имеет длину inp_L * 2 (Re, Im, Re, Im, ...)
 	    // inp содержит inp_L значений uint32_t
@@ -25,8 +27,8 @@ void FFT_fp(uint32_t* inp, uint32_t inp_L, uint32_t* buf){
 
 	    // --- копирование входных данных в буфер ---
 	    for (i = 0; i < inp_L; i++) {
-	        buf[i * 2]     = (int)inp[i];  // Re
+	        buf[i * 2]     = inp[i];
-	        buf[i * 2 + 1] = 0;            // Im = 0
+	        buf[i * 2 + 1] = 0;
 	    }
 
 	    // --- bit-reversal перестановка ---
@@ -39,8 +41,8 @@ void FFT_fp(uint32_t* inp, uint32_t inp_L, uint32_t* buf){
 	        }
 	        j |= bit;
 	        if (i < j) {
-	            int tmp_re = buf[i * 2];
+	            int64_t tmp_re = buf[i * 2];
-	            int tmp_im = buf[i * 2 + 1];
+	            int64_t tmp_im = buf[i * 2 + 1];
 	            buf[i * 2]     = buf[j * 2];
 	            buf[i * 2 + 1] = buf[j * 2 + 1];
 	            buf[j * 2]     = tmp_re;
@@ -53,83 +55,85 @@ void FFT_fp(uint32_t* inp, uint32_t inp_L, uint32_t* buf){
 	    while (m <= N) {
 	        uint32_t half = m >> 1;
 
-	        int c_delta_FP = cos_delta_FP_arr[m - 2];
-	        int s_delta_FP = sin_delta_FP_arr[m - 2];
-
 	        for (uint32_t start = 0; start < N; start += m) {
-	            int wr = FP_acc;
+            int64_t *twiddle_re = wr_arr[m - 2];
-	            int wi = 0;
+            int64_t *twiddle_im = wi_arr[m - 2];
 
-	            for (uint32_t k = 0; k < half; k++) {
+            for (uint32_t k = 0; k < half; k++) {
-	                int u_re = buf[(start + k) * 2];
+                int64_t wr = twiddle_re[k];
-	                int u_im = buf[(start + k) * 2 + 1];
+                int64_t wi = twiddle_im[k];
-	                int v_re = buf[(start + k + half) * 2];
+                int64_t u_re = buf[(start + k) * 2];
-	                int v_im = buf[(start + k + half) * 2 + 1];
+                int64_t u_im = buf[(start + k) * 2 + 1];
+                int64_t v_re = buf[(start + k + half) * 2];
+                int64_t v_im = buf[(start + k + half) * 2 + 1];
 
 	                // t = w * v  (в фиксированной точке)
-	                int64_t t_re = ((int64_t)wr * v_re - (int64_t)wi * v_im) / FP_acc;
+	                int64_t t_re = (wr * v_re - wi * v_im) / FP_acc;
-	                int64_t t_im = ((int64_t)wr * v_im + (int64_t)wi * v_re) / FP_acc;
+	                int64_t t_im = (wr * v_im + wi * v_re) / FP_acc;
 
 	                // верх/низ
-	                buf[(start + k) * 2]              = u_re + (int)t_re;
+	                buf[(start + k) * 2]              = u_re + t_re;
-	                buf[(start + k) * 2 + 1]          = u_im + (int)t_im;
+	                buf[(start + k) * 2 + 1]          = u_im + t_im;
-	                buf[(start + k + half) * 2]       = u_re - (int)t_re;
+	                buf[(start + k + half) * 2]       = u_re - t_re;
-	                buf[(start + k + half) * 2 + 1]   = u_im - (int)t_im;
+	                buf[(start + k + half) * 2 + 1]   = u_im - t_im;
 
-	                // w *= w_m (обновление twiddle)
+            }
-	                int64_t wr_new = ((int64_t)wr * c_delta_FP - (int64_t)wi * s_delta_FP) / FP_acc;
+        }
-	                int64_t wi_new = ((int64_t)wr * s_delta_FP + (int64_t)wi * c_delta_FP) / FP_acc;
+        m <<= 1;
-	                wr = (int)wr_new;
+    }
-	                wi = (int)wi_new;
-	            }
-	        }
-	        m <<= 1;
-	    }
 	    for (uint32_t i = 0; i < inp_L; ++i){
 	    	//buf[i*2] /= inp_L;
 	    	//buf[i*2+1] /= inp_L;
-	    	printf("re,im: %d, %d\n", buf[i*2], buf[i*2 +1]);
+	    	printf("re,im: %lld, %lld\n", (long long)buf[i*2], (long long)buf[i*2 +1]);
 	    }
 
 }
 
-void imagery2abs(uint32_t* inp, uint32_t inp_L, uint32_t *out){
+void imagery2abs(int64_t* inp, uint32_t inp_L, int64_t *out){
 	printf("+++++++++++++++++++++\n");
 	printf("calculating abs^2\n");
 	for (uint32_t i = 0; i < inp_L; ++i){
-		int val = (inp[i*2]*inp[i*2] + inp[i*2 +1]*inp[i*2 +1])/FP_acc;
+		int64_t re = inp[i*2];
-		printf("%d\n", val);
+		int64_t im = inp[i*2 +1];
+		int64_t val = (re * re + im * im) / FP_acc;
+		printf("%lld\n", (long long)val);
 		out[i] = val;
 	}
 }
 
 
 
-void sin_cos_filler(int* sin_arr, int* cos_arr, uint32_t L){
+void sin_cos_filler(int64_t* sin_arr, int64_t* cos_arr, uint32_t L){
 	//[int(-sin(2.0 * pi / m) * FP_acc) for m in range(2,inp_L//2 + 2)]
 	for (uint32_t i = 0; i < L; ++i){
 		int m = i + 2;
 		double angle = 2.0* PI/m;
 		sin_arr[i] = lround(-sin(angle) * FP_acc);
 		cos_arr[i] = lround(cos(angle) * FP_acc);
-		printf("i, angle, sin, cos: %d %g %d %d\n", i, angle, sin_arr[i], cos_arr[i]);
+		uint32_t half = m >> 1;
+		for (uint32_t k = 0; k < half; ++k){
+			double tw_angle = angle * k;
+			wr_arr[i][k] = lround(cos(tw_angle) * FP_acc);
+			wi_arr[i][k] = lround(-sin(tw_angle) * FP_acc);
+		}
+		printf("i, angle, sin, cos: %d %g %lld %lld\n", i, angle, (long long)sin_arr[i], (long long)cos_arr[i]);
 	}
 }
 
-void data_generator(uint32_t* X, uint32_t* Y, uint32_t N){
+void data_generator(int64_t* X, int64_t* Y, uint32_t N){
 	for (int i = 0; i < N; ++i){
-		X[i] = (int) i;
+		X[i] = (int64_t)i;
 		Y[i] = lround(sin(((double)i)*2.0* PI/(N/10))*FP_acc);
-//		Y[I] += 10*FP_acc;
+		Y[i] += 1*FP_acc;
 	}
 }
 
 void main(){
 	char* logfilename = "tmp";
-	uint32_t data_X[DATA_L] = {0,};
+	int64_t data_X[DATA_L] = {0,};
-	uint32_t data_Y[DATA_L] = {0,};
+	int64_t data_Y[DATA_L] = {0,};
-	uint32_t data_res_FFT_imag[DATA_L*2] = {0,};
+	int64_t data_res_FFT_imag[DATA_L*2] = {0,};
-	uint32_t data_res_FFT_abs[DATA_L] = {0,};
+	int64_t data_res_FFT_abs[DATA_L] = {0,};
 
 	sin_cos_filler(sin_delta_FP_arr, cos_delta_FP_arr, DATA_L);
 
@@ -145,8 +149,7 @@ void main(){
     logfile_ptr = fopen(logfilename, "w");
     fprintf(logfile_ptr, "X, Y, FFT\n");
 	for (uint32_t i = 0; i < DATA_L; ++i){
-		fprintf(logfile_ptr, "%d, %d, %d \n", data_X[i], data_Y[i],data_res_FFT_abs[i]);
+		fprintf(logfile_ptr, "%lld, %lg, %lg \n", (long long)data_X[i], ((double)data_Y[i])/(double)FP_acc , (double)data_res_FFT_abs[i]/(double)FP_acc);
 	}
 	fclose(logfile_ptr);
 }
-