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-rw-r--r--ccan/strgrp/_info63
1 files changed, 35 insertions, 28 deletions
diff --git a/ccan/strgrp/_info b/ccan/strgrp/_info
index b58344fc..98f9bb2b 100644
--- a/ccan/strgrp/_info
+++ b/ccan/strgrp/_info
@@ -13,10 +13,12 @@
* steps:
*
* 1. For all known strings, calculate the normalised LCS value against the
- * input string
+ * input string
+ *
* 2. Find the maximum normalised LCS value and associated group
- * 3. If the calculated normalised LCS value exceeds the configured threshold,
- * add the input string to the group, otherwise create a new group
+ *
+ * 3. If the calculated maximum normalised LCS value exceeds the configured
+ * threshold add the input string to the group, otherwise create a new group
*
* The clustering operation is expensive; LCS on its own is computationally
* O(mn) on its two input strings and optimally requires O(min(m,n)) memory. In
@@ -26,29 +28,27 @@
*
* strgrp tries to battle this complexity on several fronts:
*
- * 1. Coarse reduction of the required comparisons
- * 1a. Each group has a 'key', which is the string that triggered the creation
- * of the group
- * 1b. Input strings are only compared against group keys rather than all known
- * strings, reducing the complexity to the current number of groups rather
- * than all known strings. Note due the pathological case where the number
- * of groups is equal to the number of known strings the algorithm still
- * has O(n^2) computational complexity
+ * 1. Coarse reduction of the required comparisons. Each group has a 'key',
+ * which is the string that triggered the creation of the group. Input strings
+ * are only compared against group keys rather than all known strings, reducing
+ * the complexity to the current number of groups rather than all known
+ * strings. Note due the pathological case where the number of groups is equal
+ * to the number of known strings the algorithm still has O(n^2) computational
+ * complexity
*
* 2. Elimination of LCS computations that will never breach the configured
- * threshold
- * 2a. This can be measured from the length of the compared strings
- * 2b. This avoids invoking the O(mn) behaviour of LCS
+ * threshold. This property can be measured from the length of the input
+ * strings, and a negative result avoids invoking the O(mn) behaviour of LCS
*
- * 3. Caching of input strings and their associated group
- * 3a. By incurring the cost of a map's string hash function we may eliminate
- * all calls to the LCS function for exact matches, potentially reducing
- * the insertion to a constant-time operation.
+ * 3. Caching of input strings and their associated group. By incurring the
+ * cost of a map's string hash function we may eliminate all calls to the LCS
+ * function for exact matches, potentially reducing the insertion to a
+ * constant-time operation.
*
* 4. Whilst the data dependencies of LCS prevent internally parallel
- * implementations, LCS as a function can be applied in parallel. The code
- * uses OpenMP to automatically and concurrently distribute scoring of the
- * input string against group keys across threads.
+ * implementations, LCS as a function can be applied in parallel. The code
+ * uses OpenMP to automatically distribute scoring of the input string
+ * against group keys across a number of threads.
*
* [1] https://en.wikipedia.org/wiki/Longest_common_subsequence_problem
*
@@ -56,10 +56,18 @@
* Author: Andrew Jeffery <andrew@aj.id.au>
*
* Example:
+ * FILE *const f;
+ * char *buf;
+ * struct strgrp *ctx;
+ * struct strgrp_iter *iter;
+ * const struct strgrp_grp *grp;
+ * struct strgrp_grp_iter *grp_iter;
+ * const struct strgrp_item *item;
+ *
+ * f = fdopen(0, "r");
* #define BUF_SIZE 512
- * FILE *const f = fdopen(0, "r");
- * char *buf = malloc(BUF_SIZE);
- * struct strgrp *ctx = strgrp_new(0.85);
+ * buf = malloc(BUF_SIZE);
+ * ctx = strgrp_new(0.85);
* while(fgets(buf, BUF_SIZE, f)) {
* buf[strcspn(buf, "\r\n")] = '\0';
* if (!strgrp_add(ctx, buf, NULL)) {
@@ -69,17 +77,16 @@
*
* // Re-implement something similar to strgrp_print() via API as an
* // example
- * struct strgrp_iter *iter = strgrp_iter_new(ctx);
- * const struct strgrp_grp *grp;
+ * *iter = strgrp_iter_new(ctx);
* while(NULL != (grp = strgrp_iter_next(iter))) {
* printf("%s\n", strgrp_grp_key(grp));
- * struct strgrp_grp_iter *grp_iter = strgrp_grp_iter_new(grp);
- * const struct strgrp_item *item;
+ * *grp_iter = strgrp_grp_iter_new(grp);
* while(NULL != (item = strgrp_grp_iter_next(grp_iter))) {
* printf("\t%s\n", strgrp_item_key(item));
* }
* strgrp_grp_iter_free(grp_iter);
* }
+ *
* strgrp_iter_free(iter);
* strgrp_free(ctx);
* free(buf);