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ticket:10081: stable sort via insertion sort with binary search; test…
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… it well

git-svn-id: http://source.icu-project.org/repos/icu/icu/trunk@33588 251d0590-4201-4cf1-90de-194747b24ca1
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schererm committed May 3, 2013
1 parent e89790a commit 7852f5a
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Showing 2 changed files with 197 additions and 25 deletions.
91 changes: 69 additions & 22 deletions source/common/uarrsort.c
View file
@@ -1,7 +1,7 @@
/*
*******************************************************************************
*
* Copyright (C) 2003, International Business Machines
* Copyright (C) 2003-2013, International Business Machines
* Corporation and others. All Rights Reserved.
*
*******************************************************************************
Expand Down Expand Up @@ -51,29 +51,77 @@ uprv_uint32Comparator(const void *context, const void *left, const void *right)
}
}

/* Straight insertion sort from Knuth vol. III, pg. 81 ---------------------- */
/* Insertion sort using binary search --------------------------------------- */

static void
doInsertionSort(char *array, int32_t start, int32_t limit, int32_t itemSize,
UComparator *cmp, const void *context, void *pv) {
int32_t i, j;
/* TODO: Make this binary search function more generally available in ICU. */
/**
* Much like Java Collections.binarySearch(List, Element, Comparator).
*
* @return the index>=0 where the item was found:
* the largest such index, if multiple, for stable sorting;
* or the index<0 for inserting the item at ~index in sorted order
*/
static int32_t
binarySearch(char *array, int32_t limit, int32_t itemSize, void *item,
UComparator *cmp, const void *context) {
int32_t start=0;
UBool found=FALSE;

/* Binary search until we get down to a tiny sub-array. */
while((limit-start)>8) {
int32_t i=(start+limit)/2;
int32_t diff=cmp(context, item, array+i*itemSize);
if(diff==0) {
/*
* Found the item. We look for the *last* occurrence of such
* an item, for stable sorting.
* If we knew that there will be only few equal items,
* we could break now and enter the linear search.
* However, if there are many equal items, then it should be
* faster to continue with the binary search.
* It seems likely that we either have all unique items
* or potentially many duplicates.
*/
found=TRUE;
start=i+1;
} else if(diff<0) {
limit=i;
} else {
start=i;
}
}

for(j=start+1; j<limit; ++j) {
/* v=array[j] */
uprv_memcpy(pv, array+j*itemSize, itemSize);
/* Linear search over the remaining tiny sub-array. */
while(start<limit) {
int32_t diff=cmp(context, item, array+start*itemSize);
if(diff==0) {
found=TRUE;
} else if(diff<0) {
break;
}
++start;
}
return found ? (start-1) : ~start;
}

for(i=j; i>start; --i) {
if(/* v>=array[i-1] */ cmp(context, pv, array+(i-1)*itemSize)>=0) {
break;
}
static void
doInsertionSort(char *array, int32_t length, int32_t itemSize,
UComparator *cmp, const void *context, void *pv) {
int32_t j;

/* array[i]=array[i-1]; */
uprv_memcpy(array+i*itemSize, array+(i-1)*itemSize, itemSize);
for(j=1; j<length; ++j) {
char *item=array+j*itemSize;
int32_t insertionPoint=binarySearch(array, j, itemSize, item, cmp, context);
if(insertionPoint<0) {
insertionPoint=~insertionPoint;
} else {
++insertionPoint; /* one past the last equal item */
}

if(i!=j) {
/* array[i]=v; */
uprv_memcpy(array+i*itemSize, pv, itemSize);
if(insertionPoint<j) {
char *dest=array+insertionPoint*itemSize;
uprv_memcpy(pv, item, itemSize); /* v=array[j] */
uprv_memmove(dest+itemSize, dest, (j-insertionPoint)*itemSize);
uprv_memcpy(dest, pv, itemSize); /* array[insertionPoint]=v */
}
}
}
Expand All @@ -95,7 +143,7 @@ insertionSort(char *array, int32_t length, int32_t itemSize,
}
}

doInsertionSort(array, 0, length, itemSize, cmp, context, pv);
doInsertionSort(array, length, itemSize, cmp, context, pv);

if(pv!=v) {
uprv_free(pv);
Expand Down Expand Up @@ -125,7 +173,7 @@ subQuickSort(char *array, int32_t start, int32_t limit, int32_t itemSize,
/* start and left are inclusive, limit and right are exclusive */
do {
if((start+MIN_QSORT)>=limit) {
doInsertionSort(array, start, limit, itemSize, cmp, context, px);
doInsertionSort(array+start*itemSize, limit-start, itemSize, cmp, context, px);
break;
}

Expand Down Expand Up @@ -229,7 +277,6 @@ uprv_sortArray(void *array, int32_t length, int32_t itemSize,
return;
} else if(length<MIN_QSORT || sortStable) {
insertionSort((char *)array, length, itemSize, cmp, context, pErrorCode);
/* could add heapSort or similar for stable sorting of longer arrays */
} else {
quickSort((char *)array, length, itemSize, cmp, context, pErrorCode);
}
Expand Down
131 changes: 128 additions & 3 deletions source/test/cintltst/sorttest.c
View file
@@ -1,11 +1,11 @@
/*
*******************************************************************************
*
* Copyright (C) 2003, International Business Machines
* Copyright (C) 2003-2013, International Business Machines
* Corporation and others. All Rights Reserved.
*
*******************************************************************************
* file name: csorttst.c
* file name: sorttest.c
* encoding: US-ASCII
* tab size: 8 (not used)
* indentation:4
Expand All @@ -16,15 +16,19 @@
* Test internal sorting functions.
*/

#include <stdio.h>

#include "unicode/utypes.h"
#include "unicode/ucol.h"
#include "unicode/ustring.h"
#include "cmemory.h"
#include "cintltst.h"
#include "uarrsort.h"

#define LENGTHOF(array) (int32_t)(sizeof(array)/sizeof((array)[0]))

static void
SortTest(void) {
SortTest() {
uint16_t small[]={ 8, 1, 2, 5, 4, 3, 7, 6 };
int32_t medium[]={ 10, 8, 1, 2, 5, 5, -1, 6, 4, 3, 9, 7, 5 };
uint32_t large[]={ 21, 10, 20, 19, 11, 12, 13, 10, 10, 10, 10,
Expand Down Expand Up @@ -80,10 +84,131 @@ SortTest(void) {
}
}

#if !UCONFIG_NO_COLLATION

/*
* Fill an array with semi-random short strings.
* Vary them enough to be interesting, but create duplicates.
* With CYCLE=10 characters per STR_LEN=3 string positions there are only 1000 unique strings.
* NUM_LINES should be larger than this.
*/
#define NUM_LINES 10000
#define STR_LEN 3
#define CYCLE 10

/*
* Use characters beyond the Latin Extended A block to avoid a collator fastpath.
* They should sort unique, so that we can later use a binary comparison for string equality.
*/
#define BASE_CHAR 0x200

typedef struct Line {
UChar s[STR_LEN];
int32_t recordNumber;
} Line;

static void
printLines(const Line *lines) {
#if 0
int32_t i, j;
for(i=0; i<NUM_LINES; ++i) {
const Line *line=lines+i;
for(j=0; j<STR_LEN; ++j) {
printf("%04x ", line->s[j]);
}
printf(" #%5d\n", line->recordNumber);
}
#endif
}

/* Use a collator so that the comparisons are not essentially free, for simple benchmarking. */
static int32_t U_EXPORT2
linesComparator(const void *context, const void *left, const void *right) {
const UCollator *coll=(const UCollator *)context;
const Line *leftLine=(const Line *)left;
const Line *rightLine=(const Line *)right;
/* compare the strings but not the record number */
return ucol_strcoll(coll, leftLine->s, STR_LEN, rightLine->s, STR_LEN);
}

static void StableSortTest() {
UErrorCode errorCode=U_ZERO_ERROR;
UCollator *coll;
Line *lines, *p;
UChar s[STR_LEN];
int32_t i, j;

coll=ucol_open("root", &errorCode);
if(U_FAILURE(errorCode)) {
log_data_err("ucol_open(root) failed - %s\n", u_errorName(errorCode));
return;
}

lines=p=(Line *)uprv_malloc(NUM_LINES*sizeof(Line));
uprv_memset(lines, 0, NUM_LINES*sizeof(Line)); /* avoid uninitialized memory */

for(j=0; j<STR_LEN; ++j) { s[j]=BASE_CHAR; }
j=0;
for(i=0; i<NUM_LINES; ++i) {
UChar c;
u_memcpy(p->s, s, STR_LEN);
p->recordNumber=i;
/* Modify the string for the next line. */
c=s[j]+1;
if(c==BASE_CHAR+CYCLE) { c=BASE_CHAR; }
s[j]=c;
if(++j==STR_LEN) { j=0; }
++p;
}
puts("\n* lines before sorting");
printLines(lines);

uprv_sortArray(lines, NUM_LINES, (int32_t)sizeof(Line),
linesComparator, coll, TRUE, &errorCode);
if(U_FAILURE(errorCode)) {
log_err("uprv_sortArray() failed - %s\n", u_errorName(errorCode));
return;
}
puts("* lines after sorting");
printLines(lines);

/* Verify that the array is sorted correctly. */
p=lines;
for(i=1; i<NUM_LINES; ++i) {
Line *q=p+1; /* =lines+i */
/* Binary comparison first, for speed. In this case, equal strings must be identical. */
int32_t diff=u_strCompare(p->s, STR_LEN, q->s, STR_LEN, FALSE);
if(diff==0) {
if(p->recordNumber>=q->recordNumber) {
log_err("equal strings %d and %d out of order at sorted index %d\n",
(int)p->recordNumber, (int)q->recordNumber, (int)i);
break;
}
} else {
/* Compare unequal strings with the collator. */
diff=ucol_strcoll(coll, p->s, STR_LEN, q->s, STR_LEN);
if(diff>=0) {
log_err("unequal strings %d and %d out of order at sorted index %d\n",
(int)p->recordNumber, (int)q->recordNumber, (int)i);
break;
}
}
p=q;
}

uprv_free(lines);
ucol_close(coll);
}

#endif /* !UCONFIG_NO_COLLATION */

void
addSortTest(TestNode** root);

void
addSortTest(TestNode** root) {
addTest(root, &SortTest, "tsutil/sorttest/SortTest");
#if !UCONFIG_NO_COLLATION
addTest(root, &StableSortTest, "tsutil/sorttest/StableSortTest");
#endif
}

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