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101 lines
3.5 KiB
C
101 lines
3.5 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2023 Justine Alexandra Roberts Tunney │
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│ │
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│ Permission to use, copy, modify, and/or distribute this software for │
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│ any purpose with or without fee is hereby granted, provided that the │
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│ above copyright notice and this permission notice appear in all copies. │
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│ │
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│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
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│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
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│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
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│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
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│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
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│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
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│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
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│ PERFORMANCE OF THIS SOFTWARE. │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/mem/alg.h"
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#include "libc/mem/mem.h"
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#include "libc/runtime/runtime.h"
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#include "libc/str/str.h"
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// Credit: Andrew Schein. 2009. Open-source C++ implementation of Radix
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// Sort for double-precision floating points. (2009).
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#define HIST_SIZE (size_t)2048
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#define get_byte_0(v) ((v)&0x7FF)
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#define get_byte_1(v) (((v) >> 11) & 0x7FF)
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#define get_byte_2_flip_sign(v) (((unsigned)(v) >> 22) ^ 0x200)
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bool radix_sort_int32(int32_t *A, size_t n) {
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int32_t *T, *reader, *writer;
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size_t i, pos, sum0, sum1, sum2, tsum, *b0, *b1, *b2;
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if (n < HIST_SIZE) {
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_intsort(A, n);
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return true;
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}
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if (!(T = (int32_t *)malloc(n * sizeof(int32_t)))) {
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return false;
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}
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if (!(b0 = (size_t *)calloc(HIST_SIZE * 3, sizeof(size_t)))) {
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free(T);
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return false;
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}
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b1 = b0 + HIST_SIZE;
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b2 = b1 + HIST_SIZE;
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for (i = 0; i < n; i++) {
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b0[get_byte_0(A[i])]++;
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b1[get_byte_1(A[i])]++;
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b2[get_byte_2_flip_sign(A[i])]++;
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}
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sum0 = sum1 = sum2 = tsum = 0;
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for (i = 0; i < HIST_SIZE; i++) {
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tsum = b0[i] + sum0;
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b0[i] = sum0 - 1;
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sum0 = tsum;
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tsum = b1[i] + sum1;
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b1[i] = sum1 - 1;
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sum1 = tsum;
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tsum = b2[i] + sum2;
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b2[i] = sum2 - 1;
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sum2 = tsum;
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}
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writer = T;
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reader = A;
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for (i = 0; i < n; i++) {
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pos = get_byte_0(reader[i]);
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writer[++b0[pos]] = reader[i];
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}
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writer = A;
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reader = T;
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for (i = 0; i < n; i++) {
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pos = get_byte_1(reader[i]);
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writer[++b1[pos]] = reader[i];
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}
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writer = T;
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reader = A;
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for (i = 0; i < n; i++) {
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pos = get_byte_2_flip_sign(reader[i]);
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writer[++b2[pos]] = reader[i];
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}
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memcpy(A, T, n * sizeof(int));
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free(b0);
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free(T);
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return true;
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}
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