cosmopolitan/third_party/python/Modules/_decimal/libmpdec/convolute.c

/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:4;tab-width:8;coding:utf-8 -*-│
│vi: set net ft=c ts=4 sts=4 sw=4 fenc=utf-8                                :vi│
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright (c) 2008-2016 Stefan Krah. All rights reserved.                    │
│                                                                              │
│ Redistribution and use in source and binary forms, with or without           │
│ modification, are permitted provided that the following conditions           │
│ are met:                                                                     │
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│ 1. Redistributions of source code must retain the above copyright            │
│    notice, this list of conditions and the following disclaimer.             │
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│ 2. Redistributions in binary form must reproduce the above copyright         │
│    notice, this list of conditions and the following disclaimer in           │
│    the documentation and/or other materials provided with the                │
│    distribution.                                                             │
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│ THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS "AS IS" AND         │
│ ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE        │
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│ PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS         │
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╚─────────────────────────────────────────────────────────────────────────────*/
#include "third_party/python/Modules/_decimal/libmpdec/bits.h"
#include "third_party/python/Modules/_decimal/libmpdec/constants.h"
#include "third_party/python/Modules/_decimal/libmpdec/convolute.h"
#include "third_party/python/Modules/_decimal/libmpdec/fnt.h"
#include "third_party/python/Modules/_decimal/libmpdec/fourstep.h"
#include "third_party/python/Modules/_decimal/libmpdec/mpdecimal.h"
#include "third_party/python/Modules/_decimal/libmpdec/numbertheory.h"
#include "third_party/python/Modules/_decimal/libmpdec/sixstep.h"
#include "third_party/python/Modules/_decimal/libmpdec/umodarith.h"
/* clang-format off */

asm(".ident\t\"\\n\\n\
libmpdec (BSD-2)\\n\
Copyright 2008-2016 Stefan Krah\"");
asm(".include \"libc/disclaimer.inc\"");


/* Bignum: Fast convolution using the Number Theoretic Transform.
   Used for the multiplication of very large coefficients. */


/* Convolute the data in c1 and c2. Result is in c1. */
int
fnt_convolute(mpd_uint_t *c1, mpd_uint_t *c2, mpd_size_t n, int modnum)
{
    int (*fnt)(mpd_uint_t *, mpd_size_t, int);
    int (*inv_fnt)(mpd_uint_t *, mpd_size_t, int);
    mpd_uint_t n_inv, umod;
    mpd_size_t i;
    SETMODULUS(modnum);
    n_inv = POWMOD(n, (umod-2));
    if (ispower2(n)) {
        if (n > SIX_STEP_THRESHOLD) {
            fnt = six_step_fnt;
            inv_fnt = inv_six_step_fnt;
        }
        else {
            fnt = std_fnt;
            inv_fnt = std_inv_fnt;
        }
    }
    else {
        fnt = four_step_fnt;
        inv_fnt = inv_four_step_fnt;
    }
    if (!fnt(c1, n, modnum)) {
        return 0;
    }
    if (!fnt(c2, n, modnum)) {
        return 0;
    }
    for (i = 0; i < n-1; i += 2) {
        mpd_uint_t x0 = c1[i];
        mpd_uint_t y0 = c2[i];
        mpd_uint_t x1 = c1[i+1];
        mpd_uint_t y1 = c2[i+1];
        MULMOD2(&x0, y0, &x1, y1);
        c1[i] = x0;
        c1[i+1] = x1;
    }
    if (!inv_fnt(c1, n, modnum)) {
        return 0;
    }
    for (i = 0; i < n-3; i += 4) {
        mpd_uint_t x0 = c1[i];
        mpd_uint_t x1 = c1[i+1];
        mpd_uint_t x2 = c1[i+2];
        mpd_uint_t x3 = c1[i+3];
        MULMOD2C(&x0, &x1, n_inv);
        MULMOD2C(&x2, &x3, n_inv);
        c1[i] = x0;
        c1[i+1] = x1;
        c1[i+2] = x2;
        c1[i+3] = x3;
    }
    return 1;
}

/* Autoconvolute the data in c1. Result is in c1. */
int
fnt_autoconvolute(mpd_uint_t *c1, mpd_size_t n, int modnum)
{
    int (*fnt)(mpd_uint_t *, mpd_size_t, int);
    int (*inv_fnt)(mpd_uint_t *, mpd_size_t, int);
    mpd_uint_t n_inv, umod;
    mpd_size_t i;
    SETMODULUS(modnum);
    n_inv = POWMOD(n, (umod-2));
    if (ispower2(n)) {
        if (n > SIX_STEP_THRESHOLD) {
            fnt = six_step_fnt;
            inv_fnt = inv_six_step_fnt;
        }
        else {
            fnt = std_fnt;
            inv_fnt = std_inv_fnt;
        }
    }
    else {
        fnt = four_step_fnt;
        inv_fnt = inv_four_step_fnt;
    }
    if (!fnt(c1, n, modnum)) {
        return 0;
    }
    for (i = 0; i < n-1; i += 2) {
        mpd_uint_t x0 = c1[i];
        mpd_uint_t x1 = c1[i+1];
        MULMOD2(&x0, x0, &x1, x1);
        c1[i] = x0;
        c1[i+1] = x1;
    }
    if (!inv_fnt(c1, n, modnum)) {
        return 0;
    }
    for (i = 0; i < n-3; i += 4) {
        mpd_uint_t x0 = c1[i];
        mpd_uint_t x1 = c1[i+1];
        mpd_uint_t x2 = c1[i+2];
        mpd_uint_t x3 = c1[i+3];
        MULMOD2C(&x0, &x1, n_inv);
        MULMOD2C(&x2, &x3, n_inv);
        c1[i] = x0;
        c1[i+1] = x1;
        c1[i+2] = x2;
        c1[i+3] = x3;
    }
    return 1;
}