diff options
Diffstat (limited to 'gsl-1.9/fft/c_pass_6.c')
| -rw-r--r-- | gsl-1.9/fft/c_pass_6.c | 220 |
1 files changed, 220 insertions, 0 deletions
diff --git a/gsl-1.9/fft/c_pass_6.c b/gsl-1.9/fft/c_pass_6.c new file mode 100644 index 0000000..02e2128 --- /dev/null +++ b/gsl-1.9/fft/c_pass_6.c @@ -0,0 +1,220 @@ +/* fft/c_pass_6.c + * + * Copyright (C) 1996, 1997, 1998, 1999, 2000 Brian Gough + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or (at + * your option) any later version. + * + * This program is distributed in the hope that it will be useful, but + * WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. + */ + +static int +FUNCTION(fft_complex,pass_6) (const BASE in[], + const size_t istride, + BASE out[], + const size_t ostride, + const gsl_fft_direction sign, + const size_t product, + const size_t n, + const TYPE(gsl_complex) twiddle1[], + const TYPE(gsl_complex) twiddle2[], + const TYPE(gsl_complex) twiddle3[], + const TYPE(gsl_complex) twiddle4[], + const TYPE(gsl_complex) twiddle5[]) +{ + + size_t i = 0, j = 0; + size_t k, k1; + + const size_t factor = 6; + const size_t m = n / factor; + const size_t q = n / product; + const size_t p_1 = product / factor; + const size_t jump = (factor - 1) * p_1; + + const ATOMIC tau = sqrt (3.0) / 2.0; + + for (k = 0; k < q; k++) + { + ATOMIC w1_real, w1_imag, w2_real, w2_imag, w3_real, w3_imag, w4_real, + w4_imag, w5_real, w5_imag; + + if (k == 0) + { + w1_real = 1.0; + w1_imag = 0.0; + w2_real = 1.0; + w2_imag = 0.0; + w3_real = 1.0; + w3_imag = 0.0; + w4_real = 1.0; + w4_imag = 0.0; + w5_real = 1.0; + w5_imag = 0.0; + } + else + { + if (sign == gsl_fft_forward) + { + /* forward tranform */ + w1_real = GSL_REAL(twiddle1[k - 1]); + w1_imag = GSL_IMAG(twiddle1[k - 1]); + w2_real = GSL_REAL(twiddle2[k - 1]); + w2_imag = GSL_IMAG(twiddle2[k - 1]); + w3_real = GSL_REAL(twiddle3[k - 1]); + w3_imag = GSL_IMAG(twiddle3[k - 1]); + w4_real = GSL_REAL(twiddle4[k - 1]); + w4_imag = GSL_IMAG(twiddle4[k - 1]); + w5_real = GSL_REAL(twiddle5[k - 1]); + w5_imag = GSL_IMAG(twiddle5[k - 1]); + } + else + { + /* backward tranform: w -> conjugate(w) */ + w1_real = GSL_REAL(twiddle1[k - 1]); + w1_imag = -GSL_IMAG(twiddle1[k - 1]); + w2_real = GSL_REAL(twiddle2[k - 1]); + w2_imag = -GSL_IMAG(twiddle2[k - 1]); + w3_real = GSL_REAL(twiddle3[k - 1]); + w3_imag = -GSL_IMAG(twiddle3[k - 1]); + w4_real = GSL_REAL(twiddle4[k - 1]); + w4_imag = -GSL_IMAG(twiddle4[k - 1]); + w5_real = GSL_REAL(twiddle5[k - 1]); + w5_imag = -GSL_IMAG(twiddle5[k - 1]); + } + } + + for (k1 = 0; k1 < p_1; k1++) + { + const ATOMIC z0_real = REAL(in,istride,i); + const ATOMIC z0_imag = IMAG(in,istride,i); + const ATOMIC z1_real = REAL(in,istride,i+m); + const ATOMIC z1_imag = IMAG(in,istride,i+m); + const ATOMIC z2_real = REAL(in,istride,i+2*m); + const ATOMIC z2_imag = IMAG(in,istride,i+2*m); + const ATOMIC z3_real = REAL(in,istride,i+3*m); + const ATOMIC z3_imag = IMAG(in,istride,i+3*m); + const ATOMIC z4_real = REAL(in,istride,i+4*m); + const ATOMIC z4_imag = IMAG(in,istride,i+4*m); + const ATOMIC z5_real = REAL(in,istride,i+5*m); + const ATOMIC z5_imag = IMAG(in,istride,i+5*m); + + /* compute x = W(6) z */ + + /* W(6) is a combination of sums and differences of W(3) acting + on the even and odd elements of z */ + + /* ta1 = z2 + z4 */ + const ATOMIC ta1_real = z2_real + z4_real; + const ATOMIC ta1_imag = z2_imag + z4_imag; + + /* ta2 = z0 - ta1/2 */ + const ATOMIC ta2_real = z0_real - ta1_real / 2; + const ATOMIC ta2_imag = z0_imag - ta1_imag / 2; + + /* ta3 = (+/-) sin(pi/3)*(z2 - z4) */ + const ATOMIC ta3_real = ((int) sign) * tau * (z2_real - z4_real); + const ATOMIC ta3_imag = ((int) sign) * tau * (z2_imag - z4_imag); + + /* a0 = z0 + ta1 */ + const ATOMIC a0_real = z0_real + ta1_real; + const ATOMIC a0_imag = z0_imag + ta1_imag; + + /* a1 = ta2 + i ta3 */ + const ATOMIC a1_real = ta2_real - ta3_imag; + const ATOMIC a1_imag = ta2_imag + ta3_real; + + /* a2 = ta2 - i ta3 */ + const ATOMIC a2_real = ta2_real + ta3_imag; + const ATOMIC a2_imag = ta2_imag - ta3_real; + + /* tb1 = z5 + z1 */ + const ATOMIC tb1_real = z5_real + z1_real; + const ATOMIC tb1_imag = z5_imag + z1_imag; + + /* tb2 = z3 - tb1/2 */ + const ATOMIC tb2_real = z3_real - tb1_real / 2; + const ATOMIC tb2_imag = z3_imag - tb1_imag / 2; + + /* tb3 = (+/-) sin(pi/3)*(z5 - z1) */ + const ATOMIC tb3_real = ((int) sign) * tau * (z5_real - z1_real); + const ATOMIC tb3_imag = ((int) sign) * tau * (z5_imag - z1_imag); + + /* b0 = z3 + tb1 */ + const ATOMIC b0_real = z3_real + tb1_real; + const ATOMIC b0_imag = z3_imag + tb1_imag; + + /* b1 = tb2 + i tb3 */ + const ATOMIC b1_real = tb2_real - tb3_imag; + const ATOMIC b1_imag = tb2_imag + tb3_real; + + /* b2 = tb2 - i tb3 */ + const ATOMIC b2_real = tb2_real + tb3_imag; + const ATOMIC b2_imag = tb2_imag - tb3_real; + + /* x0 = a0 + b0 */ + const ATOMIC x0_real = a0_real + b0_real; + const ATOMIC x0_imag = a0_imag + b0_imag; + + /* x4 = a1 + b1 */ + const ATOMIC x4_real = a1_real + b1_real; + const ATOMIC x4_imag = a1_imag + b1_imag; + + /* x2 = a2 + b2 */ + const ATOMIC x2_real = a2_real + b2_real; + const ATOMIC x2_imag = a2_imag + b2_imag; + + /* x3 = a0 - b0 */ + const ATOMIC x3_real = a0_real - b0_real; + const ATOMIC x3_imag = a0_imag - b0_imag; + + /* x1 = a1 - b1 */ + const ATOMIC x1_real = a1_real - b1_real; + const ATOMIC x1_imag = a1_imag - b1_imag; + + /* x5 = a2 - b2 */ + const ATOMIC x5_real = a2_real - b2_real; + const ATOMIC x5_imag = a2_imag - b2_imag; + + /* apply twiddle factors */ + + /* to0 = 1 * x0 */ + REAL(out,ostride,j) = x0_real; + IMAG(out,ostride,j) = x0_imag; + + /* to1 = w1 * x1 */ + REAL(out,ostride,j+p_1) = w1_real * x1_real - w1_imag * x1_imag; + IMAG(out,ostride,j+p_1) = w1_real * x1_imag + w1_imag * x1_real; + + /* to2 = w2 * x2 */ + REAL(out,ostride,j+2*p_1) = w2_real * x2_real - w2_imag * x2_imag; + IMAG(out,ostride,j+2*p_1) = w2_real * x2_imag + w2_imag * x2_real; + + /* to3 = w3 * x3 */ + REAL(out,ostride,j+3*p_1) = w3_real * x3_real - w3_imag * x3_imag; + IMAG(out,ostride,j+3*p_1) = w3_real * x3_imag + w3_imag * x3_real; + + /* to4 = w4 * x4 */ + REAL(out,ostride,j+4*p_1) = w4_real * x4_real - w4_imag * x4_imag; + IMAG(out,ostride,j+4*p_1) = w4_real * x4_imag + w4_imag * x4_real; + + /* to5 = w5 * x5 */ + REAL(out,ostride,j+5*p_1) = w5_real * x5_real - w5_imag * x5_imag; + IMAG(out,ostride,j+5*p_1) = w5_real * x5_imag + w5_imag * x5_real; + + i++; + j++; + } + j += jump; + } + return 0; +} |