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/**
@file
@ingroup cudd
@brief Functions for cache insertion and lookup.
@author Fabio Somenzi
@copyright@parblock
Copyright (c) 1995-2015, Regents of the University of Colorado
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
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.
Neither the name of the University of Colorado nor the names of its
contributors may be used to endorse or promote products derived from
this software without specific prior written permission.
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 OWNER 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.
@endparblock
*/
#include "util.h"
#include "cuddInt.h"
/*---------------------------------------------------------------------------*/
/* Constant declarations */
/*---------------------------------------------------------------------------*/
#ifdef DD_CACHE_PROFILE
#define DD_HYSTO_BINS 8
#endif
/*---------------------------------------------------------------------------*/
/* Stucture declarations */
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
/* Type declarations */
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
/* Variable declarations */
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
/* Macro declarations */
/*---------------------------------------------------------------------------*/
/** \cond */
/*---------------------------------------------------------------------------*/
/* Static function prototypes */
/*---------------------------------------------------------------------------*/
/** \endcond */
/*---------------------------------------------------------------------------*/
/* Definition of exported functions */
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
/* Definition of internal functions */
/*---------------------------------------------------------------------------*/
/**
@brief Initializes the computed table.
@details It is called by Cudd_Init.
@return 1 in case of success; 0 otherwise.
@sideeffect None
@see Cudd_Init
*/
int
cuddInitCache(
DdManager * unique /**< unique table */,
unsigned int cacheSize /**< initial size of the cache */,
unsigned int maxCacheSize /**< cache size beyond which no resizing occurs */)
{
int i;
unsigned int logSize;
#ifndef DD_CACHE_PROFILE
DdNodePtr *mem;
ptruint offset;
#endif
/* Round cacheSize to largest power of 2 not greater than the requested
** initial cache size. */
logSize = cuddComputeFloorLog2(ddMax(cacheSize,unique->slots/2));
cacheSize = 1U << logSize;
unique->acache = ALLOC(DdCache,cacheSize+1);
if (unique->acache == NULL) {
unique->errorCode = CUDD_MEMORY_OUT;
return(0);
}
/* If the size of the cache entry is a power of 2, we want to
** enforce alignment to that power of two. This happens when
** DD_CACHE_PROFILE is not defined. */
#ifdef DD_CACHE_PROFILE
unique->cache = unique->acache;
unique->memused += (cacheSize) * sizeof(DdCache);
#else
mem = (DdNodePtr *) unique->acache;
offset = (ptruint) mem & (sizeof(DdCache) - 1);
mem += (sizeof(DdCache) - offset) / sizeof(DdNodePtr);
unique->cache = (DdCache *) mem;
assert(((ptruint) unique->cache & (sizeof(DdCache) - 1)) == 0);
unique->memused += (cacheSize+1) * sizeof(DdCache);
#endif
unique->cacheSlots = cacheSize;
unique->cacheShift = sizeof(int) * 8 - logSize;
unique->maxCacheHard = maxCacheSize;
/* If cacheSlack is non-negative, we can resize. */
unique->cacheSlack = (int) ddMin(maxCacheSize,
DD_MAX_CACHE_TO_SLOTS_RATIO*unique->slots) -
2 * (int) cacheSize;
Cudd_SetMinHit(unique,DD_MIN_HIT);
/* Initialize to avoid division by 0 and immediate resizing. */
unique->cacheMisses = (double) (int) (cacheSize * unique->minHit + 1);
unique->cacheHits = 0;
unique->totCachehits = 0;
/* The sum of cacheMisses and totCacheMisses is always correct,
** even though cacheMisses is larger than it should for the reasons
** explained above. */
unique->totCacheMisses = -unique->cacheMisses;
unique->cachecollisions = 0;
unique->cacheinserts = 0;
unique->cacheLastInserts = 0;
unique->cachedeletions = 0;
/* Initialize the cache */
for (i = 0; (unsigned) i < cacheSize; i++) {
unique->cache[i].h = 0; /* unused slots */
unique->cache[i].data = NULL; /* invalid entry */
#ifdef DD_CACHE_PROFILE
unique->cache[i].count = 0;
#endif
}
return(1);
} /* end of cuddInitCache */
/**
@brief Inserts a result in the cache for a function with three
operands.
@details The operator tag (see cuddInt.h for details) is split and
stored into unused bits of the first two pointers.
@sideeffect None
@see cuddCacheInsert2 cuddCacheInsert1
*/
void
cuddCacheInsert(
DdManager * table,
ptruint op,
DdNode * f,
DdNode * g,
DdNode * h,
DdNode * data)
{
int posn;
DdCache *entry;
ptruint uf, ug, uh;
uf = (ptruint) f | (op & 0xe);
ug = (ptruint) g | (op >> 4);
uh = (ptruint) h;
posn = ddCHash2(uh,uf,ug,table->cacheShift);
entry = &table->cache[posn];
table->cachecollisions += entry->data != NULL;
table->cacheinserts++;
entry->f = (DdNode *) uf;
entry->g = (DdNode *) ug;
entry->h = uh;
entry->data = data;
#ifdef DD_CACHE_PROFILE
entry->count++;
#endif
} /* end of cuddCacheInsert */
/**
@brief Inserts a result in the cache for a function with two
operands.
@sideeffect None
@see cuddCacheInsert cuddCacheInsert1
*/
void
cuddCacheInsert2(
DdManager * table,
DD_CTFP op,
DdNode * f,
DdNode * g,
DdNode * data)
{
int posn;
DdCache *entry;
posn = ddCHash2(op,f,g,table->cacheShift);
entry = &table->cache[posn];
if (entry->data != NULL) {
table->cachecollisions++;
}
table->cacheinserts++;
entry->f = f;
entry->g = g;
entry->h = (ptruint) op;
entry->data = data;
#ifdef DD_CACHE_PROFILE
entry->count++;
#endif
} /* end of cuddCacheInsert2 */
/**
@brief Inserts a result in the cache for a function with two
operands.
@sideeffect None
@see cuddCacheInsert cuddCacheInsert2
*/
void
cuddCacheInsert1(
DdManager * table,
DD_CTFP1 op,
DdNode * f,
DdNode * data)
{
int posn;
DdCache *entry;
posn = ddCHash2(op,f,f,table->cacheShift);
entry = &table->cache[posn];
if (entry->data != NULL) {
table->cachecollisions++;
}
table->cacheinserts++;
entry->f = f;
entry->g = f;
entry->h = (ptruint) op;
entry->data = data;
#ifdef DD_CACHE_PROFILE
entry->count++;
#endif
} /* end of cuddCacheInsert1 */
/**
@brief Looks up in the cache for the result of op applied to f,
g, and h.
@return the result if found; it returns NULL if no result is found.
@sideeffect None
@see cuddCacheLookup2 cuddCacheLookup1
*/
DdNode *
cuddCacheLookup(
DdManager * table,
ptruint op,
DdNode * f,
DdNode * g,
DdNode * h)
{
int posn;
DdCache *en,*cache;
DdNode *data;
ptruint uf, ug, uh;
uf = (ptruint) f | (op & 0xe);
ug = (ptruint) g | (op >> 4);
uh = (ptruint) h;
cache = table->cache;
#ifdef DD_DEBUG
if (cache == NULL) {
return(NULL);
}
#endif
posn = ddCHash2(uh,uf,ug,table->cacheShift);
en = &cache[posn];
if (en->data != NULL && en->f==(DdNodePtr)uf && en->g==(DdNodePtr)ug &&
en->h==uh) {
data = Cudd_Regular(en->data);
table->cacheHits++;
if (data->ref == 0) {
cuddReclaim(table,data);
}
return(en->data);
}
/* Cache miss: decide whether to resize. */
table->cacheMisses++;
if (table->cacheSlack >= 0 &&
table->cacheHits > table->cacheMisses * table->minHit) {
cuddCacheResize(table);
}
return(NULL);
} /* end of cuddCacheLookup */
/**
@brief Looks up in the cache for the result of op applied to f,
g, and h.
@return the result if found; it returns NULL if no result is found.
@sideeffect None
@see cuddCacheLookup2Zdd cuddCacheLookup1Zdd
*/
DdNode *
cuddCacheLookupZdd(
DdManager * table,
ptruint op,
DdNode * f,
DdNode * g,
DdNode * h)
{
int posn;
DdCache *en,*cache;
DdNode *data;
ptruint uf, ug, uh;
uf = (ptruint) f | (op & 0xe);
ug = (ptruint) g | (op >> 4);
uh = (ptruint) h;
cache = table->cache;
#ifdef DD_DEBUG
if (cache == NULL) {
return(NULL);
}
#endif
posn = ddCHash2(uh,uf,ug,table->cacheShift);
en = &cache[posn];
if (en->data != NULL && en->f==(DdNodePtr)uf && en->g==(DdNodePtr)ug &&
en->h==uh) {
data = Cudd_Regular(en->data);
table->cacheHits++;
if (data->ref == 0) {
cuddReclaimZdd(table,data);
}
return(en->data);
}
/* Cache miss: decide whether to resize. */
table->cacheMisses++;
if (table->cacheSlack >= 0 &&
table->cacheHits > table->cacheMisses * table->minHit) {
cuddCacheResize(table);
}
return(NULL);
} /* end of cuddCacheLookupZdd */
/**
@brief Looks up in the cache for the result of op applied to f
and g.
@return the result if found; it returns NULL if no result is found.
@sideeffect None
@see cuddCacheLookup cuddCacheLookup1
*/
DdNode *
cuddCacheLookup2(
DdManager * table,
DD_CTFP op,
DdNode * f,
DdNode * g)
{
int posn;
DdCache *en,*cache;
DdNode *data;
cache = table->cache;
#ifdef DD_DEBUG
if (cache == NULL) {
return(NULL);
}
#endif
posn = ddCHash2(op,f,g,table->cacheShift);
en = &cache[posn];
if (en->data != NULL && en->f==f && en->g==g && en->h==(ptruint)op) {
data = Cudd_Regular(en->data);
table->cacheHits++;
if (data->ref == 0) {
cuddReclaim(table,data);
}
return(en->data);
}
/* Cache miss: decide whether to resize. */
table->cacheMisses++;
if (table->cacheSlack >= 0 &&
table->cacheHits > table->cacheMisses * table->minHit) {
cuddCacheResize(table);
}
return(NULL);
} /* end of cuddCacheLookup2 */
/**
@brief Looks up in the cache for the result of op applied to f.
@return the result if found; it returns NULL if no result is found.
@sideeffect None
@see cuddCacheLookup cuddCacheLookup2
*/
DdNode *
cuddCacheLookup1(
DdManager * table,
DD_CTFP1 op,
DdNode * f)
{
int posn;
DdCache *en,*cache;
DdNode *data;
cache = table->cache;
#ifdef DD_DEBUG
if (cache == NULL) {
return(NULL);
}
#endif
posn = ddCHash2(op,f,f,table->cacheShift);
en = &cache[posn];
if (en->data != NULL && en->f==f && en->h==(ptruint)op) {
data = Cudd_Regular(en->data);
table->cacheHits++;
if (data->ref == 0) {
cuddReclaim(table,data);
}
return(en->data);
}
/* Cache miss: decide whether to resize. */
table->cacheMisses++;
if (table->cacheSlack >= 0 &&
table->cacheHits > table->cacheMisses * table->minHit) {
cuddCacheResize(table);
}
return(NULL);
} /* end of cuddCacheLookup1 */
/**
@brief Looks up in the cache for the result of op applied to f
and g.
@return the result if found; it returns NULL if no result is found.
@sideeffect None
@see cuddCacheLookupZdd cuddCacheLookup1Zdd
*/
DdNode *
cuddCacheLookup2Zdd(
DdManager * table,
DD_CTFP op,
DdNode * f,
DdNode * g)
{
int posn;
DdCache *en,*cache;
DdNode *data;
cache = table->cache;
#ifdef DD_DEBUG
if (cache == NULL) {
return(NULL);
}
#endif
posn = ddCHash2(op,f,g,table->cacheShift);
en = &cache[posn];
if (en->data != NULL && en->f==f && en->g==g && en->h==(ptruint)op) {
data = Cudd_Regular(en->data);
table->cacheHits++;
if (data->ref == 0) {
cuddReclaimZdd(table,data);
}
return(en->data);
}
/* Cache miss: decide whether to resize. */
table->cacheMisses++;
if (table->cacheSlack >= 0 &&
table->cacheHits > table->cacheMisses * table->minHit) {
cuddCacheResize(table);
}
return(NULL);
} /* end of cuddCacheLookup2Zdd */
/**
@brief Looks up in the cache for the result of op applied to f.
@return the result if found; it returns NULL if no result is found.
@sideeffect None
@see cuddCacheLookupZdd cuddCacheLookup2Zdd
*/
DdNode *
cuddCacheLookup1Zdd(
DdManager * table,
DD_CTFP1 op,
DdNode * f)
{
int posn;
DdCache *en,*cache;
DdNode *data;
cache = table->cache;
#ifdef DD_DEBUG
if (cache == NULL) {
return(NULL);
}
#endif
posn = ddCHash2(op,f,f,table->cacheShift);
en = &cache[posn];
if (en->data != NULL && en->f==f && en->h==(ptruint)op) {
data = Cudd_Regular(en->data);
table->cacheHits++;
if (data->ref == 0) {
cuddReclaimZdd(table,data);
}
return(en->data);
}
/* Cache miss: decide whether to resize. */
table->cacheMisses++;
if (table->cacheSlack >= 0 &&
table->cacheHits > table->cacheMisses * table->minHit) {
cuddCacheResize(table);
}
return(NULL);
} /* end of cuddCacheLookup1Zdd */
/**
@brief Looks up in the cache for the result of op applied to f,
g, and h.
@details Assumes that the calling procedure (e.g.,
Cudd_bddIteConstant) is only interested in whether the result is
constant or not.
@return the result if found (possibly DD_NON_CONSTANT); otherwise it
returns NULL.
@sideeffect None
@see cuddCacheLookup
*/
DdNode *
cuddConstantLookup(
DdManager * table,
ptruint op,
DdNode * f,
DdNode * g,
DdNode * h)
{
int posn;
DdCache *en,*cache;
ptruint uf, ug, uh;
uf = (ptruint) f | (op & 0xe);
ug = (ptruint) g | (op >> 4);
uh = (ptruint) h;
cache = table->cache;
#ifdef DD_DEBUG
if (cache == NULL) {
return(NULL);
}
#endif
posn = ddCHash2(uh,uf,ug,table->cacheShift);
en = &cache[posn];
/* We do not reclaim here because the result should not be
* referenced, but only tested for being a constant.
*/
if (en->data != NULL &&
en->f == (DdNodePtr)uf && en->g == (DdNodePtr)ug && en->h == uh) {
table->cacheHits++;
return(en->data);
}
/* Cache miss: decide whether to resize. */
table->cacheMisses++;
if (table->cacheSlack >= 0 &&
table->cacheHits > table->cacheMisses * table->minHit) {
cuddCacheResize(table);
}
return(NULL);
} /* end of cuddConstantLookup */
/**
@brief Computes and prints a profile of the cache usage.
@return 1 if successful; 0 otherwise.
@sideeffect None
*/
int
cuddCacheProfile(
DdManager * table,
FILE * fp)
{
DdCache *cache = table->cache;
int slots = table->cacheSlots;
int nzeroes = 0;
int i, retval;
double exUsed;
#ifdef DD_CACHE_PROFILE
double count, mean, meansq, stddev, expected;
long max, min;
int imax, imin;
double *hystogramQ, *hystogramR; /* histograms by quotient and remainder */
int nbins = DD_HYSTO_BINS;
int bin;
long thiscount;
double totalcount, exStddev;
meansq = mean = expected = 0.0;
max = min = (long) cache[0].count;
imax = imin = 0;
totalcount = 0.0;
hystogramQ = ALLOC(double, nbins);
if (hystogramQ == NULL) {
table->errorCode = CUDD_MEMORY_OUT;
return(0);
}
hystogramR = ALLOC(double, nbins);
if (hystogramR == NULL) {
FREE(hystogramQ);
table->errorCode = CUDD_MEMORY_OUT;
return(0);
}
for (i = 0; i < nbins; i++) {
hystogramQ[i] = 0;
hystogramR[i] = 0;
}
for (i = 0; i < slots; i++) {
thiscount = (long) cache[i].count;
if (thiscount > max) {
max = thiscount;
imax = i;
}
if (thiscount < min) {
min = thiscount;
imin = i;
}
if (thiscount == 0) {
nzeroes++;
}
count = (double) thiscount;
mean += count;
meansq += count * count;
totalcount += count;
expected += count * (double) i;
bin = (i * nbins) / slots;
hystogramQ[bin] += (double) thiscount;
bin = i % nbins;
hystogramR[bin] += (double) thiscount;
}
mean /= (double) slots;
meansq /= (double) slots;
/* Compute the standard deviation from both the data and the
** theoretical model for a random distribution. */
stddev = sqrt(meansq - mean*mean);
exStddev = sqrt((1 - 1/(double) slots) * totalcount / (double) slots);
retval = fprintf(fp,"Cache average accesses = %g\n", mean);
if (retval == EOF) return(0);
retval = fprintf(fp,"Cache access standard deviation = %g ", stddev);
if (retval == EOF) return(0);
retval = fprintf(fp,"(expected = %g)\n", exStddev);
if (retval == EOF) return(0);
retval = fprintf(fp,"Cache max accesses = %ld for slot %d\n", max, imax);
if (retval == EOF) return(0);
retval = fprintf(fp,"Cache min accesses = %ld for slot %d\n", min, imin);
if (retval == EOF) return(0);
exUsed = 100.0 * (1.0 - exp(-totalcount / (double) slots));
retval = fprintf(fp,"Cache used slots = %.2f%% (expected %.2f%%)\n",
100.0 - (double) nzeroes * 100.0 / (double) slots,
exUsed);
if (retval == EOF) return(0);
if (totalcount > 0) {
expected /= totalcount;
retval = fprintf(fp,"Cache access hystogram for %d bins", nbins);
if (retval == EOF) return(0);
retval = fprintf(fp," (expected bin value = %g)\nBy quotient:",
expected);
if (retval == EOF) return(0);
for (i = nbins - 1; i>=0; i--) {
retval = fprintf(fp," %.0f", hystogramQ[i]);
if (retval == EOF) return(0);
}
retval = fprintf(fp,"\nBy residue: ");
if (retval == EOF) return(0);
for (i = nbins - 1; i>=0; i--) {
retval = fprintf(fp," %.0f", hystogramR[i]);
if (retval == EOF) return(0);
}
retval = fprintf(fp,"\n");
if (retval == EOF) return(0);
}
FREE(hystogramQ);
FREE(hystogramR);
#else
for (i = 0; i < slots; i++) {
nzeroes += cache[i].h == 0;
}
exUsed = 100.0 *
(1.0 - exp(-(table->cacheinserts - table->cacheLastInserts) /
(double) slots));
retval = fprintf(fp,"Cache used slots = %.2f%% (expected %.2f%%)\n",
100.0 - (double) nzeroes * 100.0 / (double) slots,
exUsed);
if (retval == EOF) return(0);
#endif
return(1);
} /* end of cuddCacheProfile */
/**
@brief Resizes the cache.
@sideeffect None
*/
void
cuddCacheResize(
DdManager * table)
{
DdCache *cache, *oldcache, *oldacache, *entry, *old;
int i;
int posn, shift;
unsigned int slots, oldslots;
double offset;
int moved = 0;
extern DD_OOMFP MMoutOfMemory;
DD_OOMFP saveHandler;
#ifndef DD_CACHE_PROFILE
ptruint misalignment;
DdNodePtr *mem;
#endif
oldcache = table->cache;
oldacache = table->acache;
oldslots = table->cacheSlots;
slots = table->cacheSlots = oldslots << 1;
#ifdef DD_VERBOSE
(void) fprintf(table->err,"Resizing the cache from %d to %d entries\n",
oldslots, slots);
(void) fprintf(table->err,
"\thits = %g\tmisses = %g\thit ratio = %5.3f\n",
table->cacheHits, table->cacheMisses,
table->cacheHits / (table->cacheHits + table->cacheMisses));
#endif
saveHandler = MMoutOfMemory;
MMoutOfMemory = table->outOfMemCallback;
table->acache = cache = ALLOC(DdCache,slots+1);
MMoutOfMemory = saveHandler;
/* If we fail to allocate the new table we just give up. */
if (cache == NULL) {
#ifdef DD_VERBOSE
(void) fprintf(table->err,"Resizing failed. Giving up.\n");
#endif
table->cacheSlots = oldslots;
table->acache = oldacache;
/* Do not try to resize again. */
table->maxCacheHard = oldslots - 1;
table->cacheSlack = - (int) (oldslots + 1);
return;
}
/* If the size of the cache entry is a power of 2, we want to
** enforce alignment to that power of two. This happens when
** DD_CACHE_PROFILE is not defined. */
#ifdef DD_CACHE_PROFILE
table->cache = cache;
#else
mem = (DdNodePtr *) cache;
misalignment = (ptruint) mem & (sizeof(DdCache) - 1);
mem += (sizeof(DdCache) - misalignment) / sizeof(DdNodePtr);
table->cache = cache = (DdCache *) mem;
assert(((ptruint) table->cache & (sizeof(DdCache) - 1)) == 0);
#endif
shift = --(table->cacheShift);
table->memused += (slots - oldslots) * sizeof(DdCache);
table->cacheSlack -= slots; /* need these many slots to double again */
/* Clear new cache. */
for (i = 0; (unsigned) i < slots; i++) {
cache[i].data = NULL;
cache[i].h = 0;
#ifdef DD_CACHE_PROFILE
cache[i].count = 0;
#endif
}
/* Copy from old cache to new one. */
for (i = 0; (unsigned) i < oldslots; i++) {
old = &oldcache[i];
if (old->data != NULL) {
posn = ddCHash2(old->h,old->f,old->g,shift);
entry = &cache[posn];
entry->f = old->f;
entry->g = old->g;
entry->h = old->h;
entry->data = old->data;
#ifdef DD_CACHE_PROFILE
entry->count = 1;
#endif
moved++;
}
}
FREE(oldacache);
/* Reinitialize measurements so as to avoid division by 0 and
** immediate resizing.
*/
offset = (double) (int) (slots * table->minHit + 1);
table->totCacheMisses += table->cacheMisses - offset;
table->cacheMisses = offset;
table->totCachehits += table->cacheHits;
table->cacheHits = 0;
table->cacheLastInserts = table->cacheinserts - (double) moved;
} /* end of cuddCacheResize */
/**
@brief Flushes the cache.
@sideeffect None
*/
void
cuddCacheFlush(
DdManager * table)
{
int i, slots;
DdCache *cache;
slots = table->cacheSlots;
cache = table->cache;
for (i = 0; i < slots; i++) {
table->cachedeletions += cache[i].data != NULL;
cache[i].data = NULL;
}
table->cacheLastInserts = table->cacheinserts;
return;
} /* end of cuddCacheFlush */
/**
@brief Returns the floor of the logarithm to the base 2.
@details The input value is assumed to be greater than 0.
@sideeffect None
*/
int
cuddComputeFloorLog2(
unsigned int value)
{
int floorLog = 0;
#ifdef DD_DEBUG
assert(value > 0);
#endif
while (value > 1) {
floorLog++;
value >>= 1;
}
return(floorLog);
} /* end of cuddComputeFloorLog2 */
/*---------------------------------------------------------------------------*/
/* Definition of static functions */
/*---------------------------------------------------------------------------*/