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//------------------------------------------------------------------------------
// GB_binary_search.h: binary search in a sorted list
//------------------------------------------------------------------------------
// SuiteSparse:GraphBLAS, Timothy A. Davis, (c) 2017-2022, All Rights Reserved.
// SPDX-License-Identifier: Apache-2.0
//------------------------------------------------------------------------------
#ifndef GB_BINARY_SEARCH_H
#define GB_BINARY_SEARCH_H
//------------------------------------------------------------------------------
// GB_TRIM_BINARY_SEARCH: simple binary search
//------------------------------------------------------------------------------
// search for integer i in the list X [pleft...pright]; no zombies.
// The list X [pleft ... pright] is in ascending order. It may have
// duplicates.
#define GB_TRIM_BINARY_SEARCH(i,X,pleft,pright) \
{ \
/* binary search of X [pleft ... pright] for integer i */ \
while (pleft < pright) \
{ \
int64_t pmiddle = (pleft + pright) / 2 ; \
if (X [pmiddle] < i) \
{ \
/* if in the list, it appears in [pmiddle+1..pright] */ \
pleft = pmiddle + 1 ; \
} \
else \
{ \
/* if in the list, it appears in [pleft..pmiddle] */ \
pright = pmiddle ; \
} \
} \
/* binary search is narrowed down to a single item */ \
/* or it has found the list is empty */ \
ASSERT (pleft == pright || pleft == pright + 1) ; \
}
//------------------------------------------------------------------------------
// GB_BINARY_SEARCH: binary search and check if found
//------------------------------------------------------------------------------
// If found is true then X [pleft == pright] == i. If duplicates appear then
// X [pleft] is any one of the entries with value i in the list.
// If found is false then
// X [original_pleft ... pleft-1] < i and
// X [pleft+1 ... original_pright] > i holds.
// The value X [pleft] may be either < or > i.
#define GB_BINARY_SEARCH(i,X,pleft,pright,found) \
{ \
GB_TRIM_BINARY_SEARCH (i, X, pleft, pright) ; \
found = (pleft == pright && X [pleft] == i) ; \
}
//------------------------------------------------------------------------------
// GB_SPLIT_BINARY_SEARCH: binary search, and then partition the list
//------------------------------------------------------------------------------
// If found is true then X [pleft] == i. If duplicates appear then X [pleft]
// is any one of the entries with value i in the list.
// If found is false then
// X [original_pleft ... pleft-1] < i and
// X [pleft ... original_pright] > i holds, and pleft-1 == pright
// If X has no duplicates, then whether or not i is found,
// X [original_pleft ... pleft-1] < i and
// X [pleft ... original_pright] >= i holds.
#define GB_SPLIT_BINARY_SEARCH(i,X,pleft,pright,found) \
{ \
GB_BINARY_SEARCH (i, X, pleft, pright, found) \
if (!found && (pleft == pright)) \
{ \
if (i > X [pleft]) \
{ \
pleft++ ; \
} \
else \
{ \
pright++ ; \
} \
} \
}
//------------------------------------------------------------------------------
// GB_TRIM_BINARY_SEARCH_ZOMBIE: binary search in the presence of zombies
//------------------------------------------------------------------------------
#define GB_TRIM_BINARY_SEARCH_ZOMBIE(i,X,pleft,pright) \
{ \
/* binary search of X [pleft ... pright] for integer i */ \
while (pleft < pright) \
{ \
int64_t pmiddle = (pleft + pright) / 2 ; \
if (i > GB_UNFLIP (X [pmiddle])) \
{ \
/* if in the list, it appears in [pmiddle+1..pright] */ \
pleft = pmiddle + 1 ; \
} \
else \
{ \
/* if in the list, it appears in [pleft..pmiddle] */ \
pright = pmiddle ; \
} \
} \
/* binary search is narrowed down to a single item */ \
/* or it has found the list is empty */ \
ASSERT (pleft == pright || pleft == pright + 1) ; \
}
//------------------------------------------------------------------------------
// GB_BINARY_SEARCH_ZOMBIE: binary search with zombies; check if found
//------------------------------------------------------------------------------
#define GB_BINARY_SEARCH_ZOMBIE(i,X,pleft,pright,found,nzombies,is_zombie) \
{ \
if (nzombies > 0) \
{ \
GB_TRIM_BINARY_SEARCH_ZOMBIE (i, X, pleft, pright) ; \
found = false ; \
is_zombie = false ; \
if (pleft == pright) \
{ \
int64_t i2 = X [pleft] ; \
is_zombie = GB_IS_ZOMBIE (i2) ; \
if (is_zombie) \
{ \
i2 = GB_FLIP (i2) ; \
} \
found = (i == i2) ; \
} \
} \
else \
{ \
is_zombie = false ; \
GB_BINARY_SEARCH(i,X,pleft,pright,found) \
} \
}
//------------------------------------------------------------------------------
// GB_SPLIT_BINARY_SEARCH_ZOMBIE: binary search with zombies; then partition
//------------------------------------------------------------------------------
#define GB_SPLIT_BINARY_SEARCH_ZOMBIE(i,X,pleft,pright,found,nzom,is_zombie) \
{ \
if (nzom > 0) \
{ \
GB_TRIM_BINARY_SEARCH_ZOMBIE (i, X, pleft, pright) ; \
found = false ; \
is_zombie = false ; \
if (pleft == pright) \
{ \
int64_t i2 = X [pleft] ; \
is_zombie = GB_IS_ZOMBIE (i2) ; \
if (is_zombie) \
{ \
i2 = GB_FLIP (i2) ; \
} \
found = (i == i2) ; \
if (!found) \
{ \
if (i > i2) \
{ \
pleft++ ; \
} \
else \
{ \
pright++ ; \
} \
} \
} \
} \
else \
{ \
is_zombie = false ; \
GB_SPLIT_BINARY_SEARCH(i,X,pleft,pright,found) \
} \
}
#endif
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