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postgres/src/backend/optimizer/geqo/geqo_main.c
Tom Lane dc43fc9b3a Suppress variable-set-but-not-used warning from clang 13. 
In the normal configuration where GEQO_DEBUG isn't defined,
recent clang versions have started to complain that geqo_main.c
accumulates the edge_failures count but never does anything
with it.  As a minimal back-patchable fix, insert a void cast
to silence this warning.  (I'd speculated about ripping out the
GEQO_DEBUG logic altogether, but I don't think we'd wish to
back-patch that.)

Per recently-established project policy, this is a candidate
for back-patching into out-of-support branches: it suppresses
an annoying compiler warning but changes no behavior.  Hence,
back-patch all the way to 9.2.

Discussion: https://postgr.es/m/CA+hUKGLTSZQwES8VNPmWO9AO0wSeLt36OCPDAZTccT1h7Q7kTQ@mail.gmail.com
2022-01-23 11:09:00 -05:00

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/*------------------------------------------------------------------------
*
* geqo_main.c
* solution to the query optimization problem
* by means of a Genetic Algorithm (GA)
*
* Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* src/backend/optimizer/geqo/geqo_main.c
*
*-------------------------------------------------------------------------
*/
/* contributed by:
=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
* Martin Utesch * Institute of Automatic Control *
= = University of Mining and Technology =
* utesch@aut.tu-freiberg.de * Freiberg, Germany *
=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
*/
/* -- parts of this are adapted from D. Whitley's Genitor algorithm -- */
#include "postgres.h"
#include <math.h>
#include "optimizer/geqo_misc.h"
#include "optimizer/geqo_mutation.h"
#include "optimizer/geqo_pool.h"
#include "optimizer/geqo_random.h"
#include "optimizer/geqo_selection.h"
/*
* Configuration options
*/
int Geqo_effort;
int Geqo_pool_size;
int Geqo_generations;
double Geqo_selection_bias;
double Geqo_seed;
static int gimme_pool_size(int nr_rel);
static int gimme_number_generations(int pool_size);
/* complain if no recombination mechanism is #define'd */
#if !defined(ERX) && \
!defined(PMX) && \
!defined(CX) && \
!defined(PX) && \
!defined(OX1) && \
!defined(OX2)
#error "must choose one GEQO recombination mechanism in geqo.h"
#endif
/*
* geqo
* solution of the query optimization problem
* similar to a constrained Traveling Salesman Problem (TSP)
*/
RelOptInfo *
geqo(PlannerInfo *root, int number_of_rels, List *initial_rels)
{
GeqoPrivateData private;
int generation;
Chromosome *momma;
Chromosome *daddy;
Chromosome *kid;
Pool *pool;
int pool_size,
number_generations;
#ifdef GEQO_DEBUG
int status_interval;
#endif
Gene *best_tour;
RelOptInfo *best_rel;
#if defined(ERX)
Edge *edge_table; /* list of edges */
int edge_failures = 0;
#endif
#if defined(CX) || defined(PX) || defined(OX1) || defined(OX2)
City *city_table; /* list of cities */
#endif
#if defined(CX)
int cycle_diffs = 0;
int mutations = 0;
#endif
/* set up private information */
root->join_search_private = (void *) &private;
private.initial_rels = initial_rels;
/* initialize private number generator */
geqo_set_seed(root, Geqo_seed);
/* set GA parameters */
pool_size = gimme_pool_size(number_of_rels);
number_generations = gimme_number_generations(pool_size);
#ifdef GEQO_DEBUG
status_interval = 10;
#endif
/* allocate genetic pool memory */
pool = alloc_pool(root, pool_size, number_of_rels);
/* random initialization of the pool */
random_init_pool(root, pool);
/* sort the pool according to cheapest path as fitness */
sort_pool(root, pool); /* we have to do it only one time, since all
* kids replace the worst individuals in
* future (-> geqo_pool.c:spread_chromo ) */
#ifdef GEQO_DEBUG
elog(DEBUG1, "GEQO selected %d pool entries, best %.2f, worst %.2f",
pool_size,
pool->data[0].worth,
pool->data[pool_size - 1].worth);
#endif
/* allocate chromosome momma and daddy memory */
momma = alloc_chromo(root, pool->string_length);
daddy = alloc_chromo(root, pool->string_length);
#if defined (ERX)
#ifdef GEQO_DEBUG
elog(DEBUG2, "using edge recombination crossover [ERX]");
#endif
/* allocate edge table memory */
edge_table = alloc_edge_table(root, pool->string_length);
#elif defined(PMX)
#ifdef GEQO_DEBUG
elog(DEBUG2, "using partially matched crossover [PMX]");
#endif
/* allocate chromosome kid memory */
kid = alloc_chromo(root, pool->string_length);
#elif defined(CX)
#ifdef GEQO_DEBUG
elog(DEBUG2, "using cycle crossover [CX]");
#endif
/* allocate city table memory */
kid = alloc_chromo(root, pool->string_length);
city_table = alloc_city_table(root, pool->string_length);
#elif defined(PX)
#ifdef GEQO_DEBUG
elog(DEBUG2, "using position crossover [PX]");
#endif
/* allocate city table memory */
kid = alloc_chromo(root, pool->string_length);
city_table = alloc_city_table(root, pool->string_length);
#elif defined(OX1)
#ifdef GEQO_DEBUG
elog(DEBUG2, "using order crossover [OX1]");
#endif
/* allocate city table memory */
kid = alloc_chromo(root, pool->string_length);
city_table = alloc_city_table(root, pool->string_length);
#elif defined(OX2)
#ifdef GEQO_DEBUG
elog(DEBUG2, "using order crossover [OX2]");
#endif
/* allocate city table memory */
kid = alloc_chromo(root, pool->string_length);
city_table = alloc_city_table(root, pool->string_length);
#endif
/* my pain main part: */
/* iterative optimization */
for (generation = 0; generation < number_generations; generation++)
{
/* SELECTION: using linear bias function */
geqo_selection(root, momma, daddy, pool, Geqo_selection_bias);
#if defined (ERX)
/* EDGE RECOMBINATION CROSSOVER */
gimme_edge_table(root, momma->string, daddy->string, pool->string_length, edge_table);
kid = momma;
/* are there any edge failures ? */
edge_failures += gimme_tour(root, edge_table, kid->string, pool->string_length);
#elif defined(PMX)
/* PARTIALLY MATCHED CROSSOVER */
pmx(root, momma->string, daddy->string, kid->string, pool->string_length);
#elif defined(CX)
/* CYCLE CROSSOVER */
cycle_diffs = cx(root, momma->string, daddy->string, kid->string, pool->string_length, city_table);
/* mutate the child */
if (cycle_diffs == 0)
{
mutations++;
geqo_mutation(root, kid->string, pool->string_length);
}
#elif defined(PX)
/* POSITION CROSSOVER */
px(root, momma->string, daddy->string, kid->string, pool->string_length, city_table);
#elif defined(OX1)
/* ORDER CROSSOVER */
ox1(root, momma->string, daddy->string, kid->string, pool->string_length, city_table);
#elif defined(OX2)
/* ORDER CROSSOVER */
ox2(root, momma->string, daddy->string, kid->string, pool->string_length, city_table);
#endif
/* EVALUATE FITNESS */
kid->worth = geqo_eval(root, kid->string, pool->string_length);
/* push the kid into the wilderness of life according to its worth */
spread_chromo(root, kid, pool);
#ifdef GEQO_DEBUG
if (status_interval && !(generation % status_interval))
print_gen(stdout, pool, generation);
#endif
}
#if defined(ERX)
#if defined(GEQO_DEBUG)
if (edge_failures != 0)
elog(LOG, "[GEQO] failures: %d, average: %d",
edge_failures, (int) number_generations / edge_failures);
else
elog(LOG, "[GEQO] no edge failures detected");
#else
/* suppress variable-set-but-not-used warnings from some compilers */
(void) edge_failures;
#endif
#endif
#if defined(CX) && defined(GEQO_DEBUG)
if (mutations != 0)
elog(LOG, "[GEQO] mutations: %d, generations: %d",
mutations, number_generations);
else
elog(LOG, "[GEQO] no mutations processed");
#endif
#ifdef GEQO_DEBUG
print_pool(stdout, pool, 0, pool_size - 1);
#endif
#ifdef GEQO_DEBUG
elog(DEBUG1, "GEQO best is %.2f after %d generations",
pool->data[0].worth, number_generations);
#endif
/*
* got the cheapest query tree processed by geqo; first element of the
* population indicates the best query tree
*/
best_tour = (Gene *) pool->data[0].string;
best_rel = gimme_tree(root, best_tour, pool->string_length);
if (best_rel == NULL)
elog(ERROR, "geqo failed to make a valid plan");
/* DBG: show the query plan */
#ifdef NOT_USED
print_plan(best_plan, root);
#endif
/* ... free memory stuff */
free_chromo(root, momma);
free_chromo(root, daddy);
#if defined (ERX)
free_edge_table(root, edge_table);
#elif defined(PMX)
free_chromo(root, kid);
#elif defined(CX)
free_chromo(root, kid);
free_city_table(root, city_table);
#elif defined(PX)
free_chromo(root, kid);
free_city_table(root, city_table);
#elif defined(OX1)
free_chromo(root, kid);
free_city_table(root, city_table);
#elif defined(OX2)
free_chromo(root, kid);
free_city_table(root, city_table);
#endif
free_pool(root, pool);
/* ... clear root pointer to our private storage */
root->join_search_private = NULL;
return best_rel;
}
/*
* Return either configured pool size or a good default
*
* The default is based on query size (no. of relations) = 2^(QS+1),
* but constrained to a range based on the effort value.
*/
static int
gimme_pool_size(int nr_rel)
{
double size;
int minsize;
int maxsize;
/* Legal pool size *must* be at least 2, so ignore attempt to select 1 */
if (Geqo_pool_size >= 2)
return Geqo_pool_size;
size = pow(2.0, nr_rel + 1.0);
maxsize = 50 * Geqo_effort; /* 50 to 500 individuals */
if (size > maxsize)
return maxsize;
minsize = 10 * Geqo_effort; /* 10 to 100 individuals */
if (size < minsize)
return minsize;
return (int) ceil(size);
}
/*
* Return either configured number of generations or a good default
*
* The default is the same as the pool size, which allows us to be
* sure that less-fit individuals get pushed out of the breeding
* population before the run finishes.
*/
static int
gimme_number_generations(int pool_size)
{
if (Geqo_generations > 0)
return Geqo_generations;
return pool_size;
}
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