/* Functions to make fuzzy comparisons between strings
- Copyright (C) 1988-1989, 1992-1993, 1995, 2001-2003, 2006, 2008
- Free Software Foundation, Inc.
+ Copyright (C) 1988-1989, 1992-1993, 1995, 2001-2003, 2006, 2008-2014 Free
+ Software Foundation, Inc.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
already allocated memory, store the allocated memory per thread. Free
it only when the thread exits. */
-static gl_tls_key_t buffer_key; /* TLS key for a 'int *' */
-static gl_tls_key_t bufmax_key; /* TLS key for a 'size_t' */
+static gl_tls_key_t buffer_key; /* TLS key for a 'int *' */
+static gl_tls_key_t bufmax_key; /* TLS key for a 'size_t' */
static void
keys_init (void)
if (lower_bound > 0)
{
/* Compute a quick upper bound.
- Each edit is an insertion or deletion of an element, hence modifies
- the length of the sequence by at most 1.
- Therefore, when starting from a sequence X and ending at a sequence Y,
- with N edits, | yvec_length - xvec_length | <= N. (Proof by
- induction over N.)
- So, at the end, we will have
- edit_count >= | xvec_length - yvec_length |.
- and hence
- result
- = (xvec_length + yvec_length - edit_count)
- / (xvec_length + yvec_length)
- <= (xvec_length + yvec_length - | yvec_length - xvec_length |)
- / (xvec_length + yvec_length)
- = 2 * min (xvec_length, yvec_length) / (xvec_length + yvec_length).
+ Each edit is an insertion or deletion of an element, hence modifies
+ the length of the sequence by at most 1.
+ Therefore, when starting from a sequence X and ending at a sequence Y,
+ with N edits, | yvec_length - xvec_length | <= N. (Proof by
+ induction over N.)
+ So, at the end, we will have
+ edit_count >= | xvec_length - yvec_length |.
+ and hence
+ result
+ = (xvec_length + yvec_length - edit_count)
+ / (xvec_length + yvec_length)
+ <= (xvec_length + yvec_length - | yvec_length - xvec_length |)
+ / (xvec_length + yvec_length)
+ = 2 * min (xvec_length, yvec_length) / (xvec_length + yvec_length).
*/
volatile double upper_bound =
- (double) (2 * MIN (xvec_length, yvec_length))
- / (xvec_length + yvec_length);
+ (double) (2 * MIN (xvec_length, yvec_length))
+ / (xvec_length + yvec_length);
if (upper_bound < lower_bound) /* Prob: 74% */
- /* Return an arbitrary value < LOWER_BOUND. */
- return 0.0;
+ /* Return an arbitrary value < LOWER_BOUND. */
+ return 0.0;
#if CHAR_BIT <= 8
/* When X and Y are both small, avoid the overhead of setting up an
- array of size 256. */
+ array of size 256. */
if (xvec_length + yvec_length >= 20) /* Prob: 99% */
- {
- /* Compute a less quick upper bound.
- Each edit is an insertion or deletion of a character, hence
- modifies the occurrence count of a character by 1 and leaves the
- other occurrence counts unchanged.
- Therefore, when starting from a sequence X and ending at a
- sequence Y, and denoting the occurrence count of C in X with
- OCC (X, C), with N edits,
- sum_C | OCC (X, C) - OCC (Y, C) | <= N.
- (Proof by induction over N.)
- So, at the end, we will have
- edit_count >= sum_C | OCC (X, C) - OCC (Y, C) |,
- and hence
- result
- = (xvec_length + yvec_length - edit_count)
- / (xvec_length + yvec_length)
- <= (xvec_length + yvec_length - sum_C | OCC(X,C) - OCC(Y,C) |)
- / (xvec_length + yvec_length).
- */
- int occ_diff[UCHAR_MAX + 1]; /* array C -> OCC(X,C) - OCC(Y,C) */
- int sum;
-
- /* Determine the occurrence counts in X. */
- memset (occ_diff, 0, sizeof (occ_diff));
- for (i = xvec_length - 1; i >= 0; i--)
- occ_diff[(unsigned char) string1[i]]++;
- /* Subtract the occurrence counts in Y. */
- for (i = yvec_length - 1; i >= 0; i--)
- occ_diff[(unsigned char) string2[i]]--;
- /* Sum up the absolute values. */
- sum = 0;
- for (i = 0; i <= UCHAR_MAX; i++)
- {
- int d = occ_diff[i];
- sum += (d >= 0 ? d : -d);
- }
-
- upper_bound = 1.0 - (double) sum / (xvec_length + yvec_length);
-
- if (upper_bound < lower_bound) /* Prob: 66% */
- /* Return an arbitrary value < LOWER_BOUND. */
- return 0.0;
- }
+ {
+ /* Compute a less quick upper bound.
+ Each edit is an insertion or deletion of a character, hence
+ modifies the occurrence count of a character by 1 and leaves the
+ other occurrence counts unchanged.
+ Therefore, when starting from a sequence X and ending at a
+ sequence Y, and denoting the occurrence count of C in X with
+ OCC (X, C), with N edits,
+ sum_C | OCC (X, C) - OCC (Y, C) | <= N.
+ (Proof by induction over N.)
+ So, at the end, we will have
+ edit_count >= sum_C | OCC (X, C) - OCC (Y, C) |,
+ and hence
+ result
+ = (xvec_length + yvec_length - edit_count)
+ / (xvec_length + yvec_length)
+ <= (xvec_length + yvec_length - sum_C | OCC(X,C) - OCC(Y,C) |)
+ / (xvec_length + yvec_length).
+ */
+ int occ_diff[UCHAR_MAX + 1]; /* array C -> OCC(X,C) - OCC(Y,C) */
+ int sum;
+
+ /* Determine the occurrence counts in X. */
+ memset (occ_diff, 0, sizeof (occ_diff));
+ for (i = xvec_length - 1; i >= 0; i--)
+ occ_diff[(unsigned char) string1[i]]++;
+ /* Subtract the occurrence counts in Y. */
+ for (i = yvec_length - 1; i >= 0; i--)
+ occ_diff[(unsigned char) string2[i]]--;
+ /* Sum up the absolute values. */
+ sum = 0;
+ for (i = 0; i <= UCHAR_MAX; i++)
+ {
+ int d = occ_diff[i];
+ sum += (d >= 0 ? d : -d);
+ }
+
+ upper_bound = 1.0 - (double) sum / (xvec_length + yvec_length);
+
+ if (upper_bound < lower_bound) /* Prob: 66% */
+ /* Return an arbitrary value < LOWER_BOUND. */
+ return 0.0;
+ }
#endif
}
/* Need more memory. */
bufmax = 2 * bufmax;
if (fdiag_len > bufmax)
- bufmax = fdiag_len;
+ bufmax = fdiag_len;
/* Calling xrealloc would be a waste: buffer's contents does not need
- to be preserved. */
+ to be preserved. */
if (buffer != NULL)
- free (buffer);
+ free (buffer);
buffer = (int *) xnmalloc (bufmax, 2 * sizeof (int));
gl_tls_set (buffer_key, buffer);
gl_tls_set (bufmax_key, (void *) (uintptr_t) bufmax);
ctxt.edit_count += ctxt.edit_count_limit;
/* The result is
- ((number of chars in common) / (average length of the strings)).
+ ((number of chars in common) / (average length of the strings)).
The numerator is
- = xvec_length - (number of calls to NOTE_DELETE)
- = yvec_length - (number of calls to NOTE_INSERT)
- = 1/2 * (xvec_length + yvec_length - (number of edits)).
+ = xvec_length - (number of calls to NOTE_DELETE)
+ = yvec_length - (number of calls to NOTE_INSERT)
+ = 1/2 * (xvec_length + yvec_length - (number of edits)).
This is admittedly biased towards finding that the strings are
similar, however it does produce meaningful results. */
return ((double) (xvec_length + yvec_length - ctxt.edit_count)
- / (xvec_length + yvec_length));
+ / (xvec_length + yvec_length));
}
projects / gnulib.git / blobdiff