greg/stasis-aries-wal
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

Binary search implementations

Browse source
This commit is contained in:
Sears Russell 2008-06-08 20:45:04 +00:00
parent 75f857bc26
commit aaf2f8bc39
1 changed files with 68 additions and 0 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

68
stasis/page/compression/binary_search.h Normal file
View file

@ -0,0 +1,68 @@
#ifndef _ROSE_COMPRESSION_BINARY_SEARCH_H__
#define _ROSE_COMPRESSION_BINARY_SEARCH_H__
// From wikipedia
int binary_search(int * A, int value, intptr_t high, intptr_t low) {
int N = high;
// low = 0;
// high = N;
while (low < high) {
intptr_t mid = low + ((high - low) / 2);
if (A[mid] < value)
low = mid + 1;
else
//can't be high = mid-1: here A[mid] >= value,
//so high can't be < mid if A[mid] == value
high = mid;
}
// high == low, using high or low depends on taste
if ((low < N) && (A[low] == value))
return low; // found
else
return -1; // not found
}
#define rose_binary_search(accessor) do{ \
int64_t bs_N = bs_high; \
int64_t bs_mid; \
while (bs_low < bs_high) { \
bs_mid = bs_low + ((bs_high - bs_low) / 2); \
if (*accessor(bs_mid) /*A[mid]*/ < bs_value) \
bs_low = bs_mid + 1; \
else \
/*can't be high = mid-1: here A[mid] >= value,*/ \
/*so high can't be < mid if A[mid] == value*/ \
bs_high = bs_mid; \
} \
/* high == low, using high or low depends on taste */ \
if ((bs_low < bs_N) && (*accessor(bs_low)/*A[low]*/ == bs_value)) \
bs_ret = bs_low; /* found */ \
else \
bs_ret = -1; /* not found */ \
} while(0)
/** Find the insertion point for a value in the array. Assumes that items stored in the array are unique. */
#define rose_binary_search_greatest_lower(accessor) do{ \
int64_t bs_N = bs_high; \
int64_t bs_mid; \
while (bs_low < bs_high) { \
bs_mid = bs_low + ((bs_high - bs_low) / 2); \
if (accessor(bs_mid) /*A[mid]*/ < bs_value) \
bs_low = bs_mid + 1; \
else \
/*can't be high = mid-1: here A[mid] >= value,*/ \
/*so high can't be < mid if A[mid] == value*/ \
bs_high = bs_mid; \
} \
/* high == low, using high or low depends on taste */ \
if ((bs_low < bs_N)) \
bs_ret = bs_low; /* found */ \
else \
bs_ret = -1; /* not found */ \
} while(0)
#endif // _ROSE_COMPRESSION_BINARY_SEARCH_H__