minix/usr.bin/nbperf/nbperf-chm.c

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/* $NetBSD: nbperf-chm.c,v 1.3 2011/10/21 23:47:11 joerg Exp $ */
/*-
* Copyright (c) 2009 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Joerg Sonnenberger.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 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.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#if HAVE_NBTOOL_CONFIG_H
#include "nbtool_config.h"
#endif
#include <sys/cdefs.h>
__RCSID("$NetBSD: nbperf-chm.c,v 1.3 2011/10/21 23:47:11 joerg Exp $");
#include <err.h>
#include <inttypes.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include "nbperf.h"
#ifdef BUILD_CHM3
#include "graph3.h"
#else
#include "graph2.h"
#endif
/*
* A full description of the algorithm can be found in:
* "An optimal algorithm for generating minimal perfect hash functions"
* by Czech, Havas and Majewski in Information Processing Letters,
* 43(5):256-264, October 1992.
*/
/*
* The algorithm is based on random, acyclic graphs.
*
* Each edge in the represents a key. The vertices are the reminder of
* the hash function mod n. n = cm with c > 2, otherwise the propability
* of finding an acyclic graph is very low (for 2-graphs). The constant
* for 3-graphs is 1.24.
*
* After the hashing phase, the graph is checked for cycles.
* A cycle-free graph is either empty or has a vertex of degree 1.
* Removing the edge for this vertex doesn't change this property,
* so applying this recursively reduces the size of the graph.
* If the graph is empty at the end of the process, it was acyclic.
*
* The assignment step now sets g[i] := 0 and processes the edges
* in reverse order of removal. That ensures that at least one vertex
* is always unvisited and can be assigned.
*/
struct state {
#ifdef BUILD_CHM3
struct graph3 graph;
#else
struct graph2 graph;
#endif
uint32_t *g;
uint8_t *visited;
};
static void
assign_nodes(struct state *state)
{
#ifdef BUILD_CHM3
struct edge3 *e;
#else
struct edge2 *e;
#endif
size_t i;
uint32_t e_idx;
for (i = 0; i < state->graph.e; ++i) {
e_idx = state->graph.output_order[i];
e = &state->graph.edges[e_idx];
#ifdef BUILD_CHM3
if (!state->visited[e->left]) {
state->g[e->left] = (2 * state->graph.e + e_idx
- state->g[e->middle] - state->g[e->right])
% state->graph.e;
} else if (!state->visited[e->middle]) {
state->g[e->middle] = (2 * state->graph.e + e_idx
- state->g[e->left] - state->g[e->right])
% state->graph.e;
} else {
state->g[e->right] = (2 * state->graph.e + e_idx
- state->g[e->left] - state->g[e->middle])
% state->graph.e;
}
state->visited[e->left] = 1;
state->visited[e->middle] = 1;
state->visited[e->right] = 1;
#else
if (!state->visited[e->left]) {
state->g[e->left] = (state->graph.e + e_idx
- state->g[e->right]) % state->graph.e;
} else {
state->g[e->right] = (state->graph.e + e_idx
- state->g[e->left]) % state->graph.e;
}
state->visited[e->left] = 1;
state->visited[e->right] = 1;
#endif
}
}
static void
print_hash(struct nbperf *nbperf, struct state *state)
{
uint32_t i, per_line;
const char *g_type;
int g_width;
fprintf(nbperf->output, "#include <stdlib.h>\n\n");
fprintf(nbperf->output, "%suint32_t\n",
nbperf->static_hash ? "static " : "");
fprintf(nbperf->output,
"%s(const void * __restrict key, size_t keylen)\n",
nbperf->hash_name);
fprintf(nbperf->output, "{\n");
if (state->graph.v >= 65536) {
g_type = "uint32_t";
g_width = 8;
per_line = 4;
} else if (state->graph.v >= 256) {
g_type = "uint16_t";
g_width = 4;
per_line = 8;
} else {
g_type = "uint8_t";
g_width = 2;
per_line = 10;
}
fprintf(nbperf->output, "\tstatic const %s g[%" PRId32 "] = {\n",
g_type, state->graph.v);
for (i = 0; i < state->graph.v; ++i) {
fprintf(nbperf->output, "%s0x%0*" PRIx32 ",%s",
(i % per_line == 0 ? "\t " : " "),
g_width, state->g[i],
(i % per_line == per_line - 1 ? "\n" : ""));
}
if (i % per_line != 0)
fprintf(nbperf->output, "\n\t};\n");
else
fprintf(nbperf->output, "\t};\n");
fprintf(nbperf->output, "\tuint32_t h[%zu];\n\n", nbperf->hash_size);
(*nbperf->print_hash)(nbperf, "\t", "key", "keylen", "h");
#ifdef BUILD_CHM3
fprintf(nbperf->output, "\treturn (g[h[0] %% %" PRIu32 "] + "
"g[h[1] %% %" PRIu32 "] + "
"g[h[2] %% %" PRIu32"]) %% %" PRIu32 ";\n",
state->graph.v, state->graph.v, state->graph.v, state->graph.e);
#else
fprintf(nbperf->output, "\treturn (g[h[0] %% %" PRIu32 "] + "
"g[h[1] %% %" PRIu32"]) %% %" PRIu32 ";\n",
state->graph.v, state->graph.v, state->graph.e);
#endif
fprintf(nbperf->output, "}\n");
if (nbperf->map_output != NULL) {
for (i = 0; i < state->graph.e; ++i)
fprintf(nbperf->map_output, "%" PRIu32 "\n", i);
}
}
int
#ifdef BUILD_CHM3
chm3_compute(struct nbperf *nbperf)
#else
chm_compute(struct nbperf *nbperf)
#endif
{
struct state state;
int retval = -1;
uint32_t v, e;
#ifdef BUILD_CHM3
if (nbperf->c == 0)
nbperf-> c = 1.24;
if (nbperf->c < 1.24)
errx(1, "The argument for option -c must be at least 1.24");
if (nbperf->hash_size < 3)
errx(1, "The hash function must generate at least 3 values");
#else
if (nbperf->c == 0)
nbperf-> c = 2;
if (nbperf->c < 2)
errx(1, "The argument for option -c must be at least 2");
if (nbperf->hash_size < 2)
errx(1, "The hash function must generate at least 2 values");
#endif
(*nbperf->seed_hash)(nbperf);
e = nbperf->n;
v = nbperf->c * nbperf->n;
#ifdef BUILD_CHM3
if (v == 1.24 * nbperf->n)
++v;
if (v < 10)
v = 10;
#else
if (v == 2 * nbperf->n)
++v;
#endif
state.g = calloc(sizeof(uint32_t), v);
state.visited = calloc(sizeof(uint8_t), v);
if (state.g == NULL || state.visited == NULL)
err(1, "malloc failed");
#ifdef BUILD_CHM3
graph3_setup(&state.graph, v, e);
if (graph3_hash(nbperf, &state.graph))
goto failed;
if (graph3_output_order(&state.graph))
goto failed;
#else
graph2_setup(&state.graph, v, e);
if (graph2_hash(nbperf, &state.graph))
goto failed;
if (graph2_output_order(&state.graph))
goto failed;
#endif
assign_nodes(&state);
print_hash(nbperf, &state);
retval = 0;
failed:
#ifdef BUILD_CHM3
graph3_free(&state.graph);
#else
graph2_free(&state.graph);
#endif
free(state.g);
free(state.visited);
return retval;
}