Commit 55dfccc1 authored by Scott Vokes's avatar Scott Vokes
Browse files

Correct hash table resizing. 

When growing the hash table, the key bumped out by Brent's variation
isn't being updated outside the insert loop. Disabling BV doesn't seem
to slow things down, so just disable it for now. Also, clear the freshly
grown hash table to NO_KEY (not 0x0 from calloc).
parent 5c8a22ca

src/lib/bus/test_yacht.c

+17 −4
Original line number Diff line number Diff line
@@ -48,9 +48,14 @@ TEST yacht_should_add_and_remove_accurately(uint8_t sz2) { 
    ASSERT(y);



    for (int i = 0; i < (1 << (sz2 - 1)); i++) {

        ASSERT(yacht_set(y, i, NULL, NULL));

        uintptr_t v = 1;

        void *old = NULL;

        ASSERT(yacht_set(y, i, (void *)v, &old));

        ASSERT_EQ(NULL, old);

        ASSERT(yacht_member(y, i));

        ASSERT(yacht_remove(y, i, NULL));

        void *old2 = NULL;

        ASSERT(yacht_remove(y, i, &old2));

        ASSERT_EQ((void *)1, old2);

        ASSERT(!yacht_member(y, i));

        /* Add it back, to ensure it isn't disturbed by other removes */

        ASSERT(yacht_set(y, i, NULL, NULL));
@@ -126,9 +131,17 @@ TEST yacht_should_grow_and_add_and_remove_accurately_out_of_order(uint8_t sz2) { 


    for (int i = 0; i < (1 << (sz2 - 1)); i++) {

        int iv = i * other_large_prime;

        ASSERT(yacht_set(y, iv, NULL, NULL));

        uintptr_t v = 1;

        void *old = NULL;

        ASSERT(yacht_set(y, iv, (void *)v, &old));

        ASSERT_EQ(NULL, old);



        ASSERT(yacht_member(y, iv));

        ASSERT(yacht_remove(y, iv, NULL));



        void *old2 = NULL;

        ASSERT(yacht_remove(y, iv, &old2));

        ASSERT_EQ((void*)v, old2);



        ASSERT(!yacht_member(y, iv));

        /* Add it back, to ensure it isn't disturbed by other removes */

        ASSERT(yacht_set(y, iv, NULL, NULL));

src/lib/bus/yacht.c

+21 −7
Original line number Diff line number Diff line
@@ -27,6 +27,8 @@ 
#define LOG(...)

#endif



#define USE_BRENTS_VARIATION 0



/* Yet Another C Hash Table:

 *   An (int set) hash table for tracking active file descriptors

 *   and their metadata. */
@@ -78,7 +80,7 @@ static size_t hash(int key) { 


bool yacht_get(struct yacht *y, int key, void **value) {

    size_t b = hash(key) & y->mask;

    LOG(" -- getting %d with bucket %d\n", key, b);

    LOG(" -- getting key %d with bucket %zd\n", key, b);



    for (size_t o = 0; o < y->size; o++) {

        size_t i = (b + o) & y->mask;  // wrap as necessary
@@ -101,7 +103,7 @@ bool yacht_member(struct yacht *y, int key) { 


/* Set KEY to VALUE in the table. */

bool yacht_set(struct yacht *y, int key, void *value, void **old_value) {

    LOG(" -- adding %d with bucket %d\n", key, b);

    LOG(" -- setting key %d\n", key);



    for (;;) {

        size_t max = y->size / 2;
@@ -123,7 +125,7 @@ static bool insert(int *buckets, void **values, 
        if (o > 0) { LOG(" -- o %zd (max_fill %zd)\n", o, max_fill); }

        size_t i = (b + o) & mask;  // wrap as necessary

        int bv = buckets[i];

        LOG(" -- b %d: %d\n", i, bv);

        LOG(" -- b %zd: %d\n", i, bv);

        if (bv == key) {

            if (old_value) { *old_value = values[i]; }

            values[i] = value;
@@ -133,18 +135,26 @@ static bool insert(int *buckets, void **values, 
            values[i] = value;

            return true;

        } else {

#if USE_BRENTS_VARIATION

            /* FIXME: This is not speeding things up significantly, and

             *     during a grow the key / value being refiled need to

             *     be updated in yacht_set or this will drop values.

             *     Disable it for now. */



            /* Brent's variation -- bump out key if not in its main spot  */

            size_t ob = hash(bv) & mask;  /* other's primary bucket */

            if (ob == i) {      /* keep looking for an open spot */

                continue;

            } else {            /* refile it instead */

                int okey = buckets[i];

                LOG(" -- SWAPPING KEYS, %d => %d\n", key, bv);

                buckets[i] = key;

                key = okey;

                void *oval = values[i];

                values[i] = value;

                value = oval;

            }

#endif

        }

    }

    return false;               /* too full */
@@ -156,8 +166,11 @@ static bool grow(struct yacht *y) { 
    size_t nmask = nsize - 1;

    int *nbuckets = NULL;

    void **nvalues = NULL;

    nbuckets = calloc(nsize, sizeof(*nbuckets));

    nbuckets = malloc(nsize * sizeof(*nbuckets));

    if (nbuckets == NULL) { return false; }

    for (int i = 0; i < nsize; i++) {

        nbuckets[i] = YACHT_NO_KEY;

    }

    nvalues = calloc(nsize, sizeof(*nvalues));

    if (nvalues == NULL) {

        free(nbuckets);
@@ -167,7 +180,7 @@ static bool grow(struct yacht *y) { 
    for (size_t i = 0; i < y->size; i++) {

        int key = y->buckets[i];

        if (key != YACHT_NO_KEY && key != YACHT_DELETED) {

            if (!insert(nbuckets, nvalues, nmask, y->size, key, y->values[i], NULL)) {

            if (!insert(nbuckets, nvalues, nmask, nsize, key, y->values[i], NULL)) {

                goto cleanup;

            }

        }
@@ -182,18 +195,19 @@ static bool grow(struct yacht *y) { 
cleanup:

    if (nbuckets) { free(nbuckets); }

    if (nvalues) { free(nvalues); }



    return false;

}



/* Remove KEY from the table. */

bool yacht_remove(struct yacht *y, int key, void **old_value) {

    size_t b = hash(key) & y->mask;

    LOG(" -- removing %d with bucket %d\n", key, b);

    LOG(" -- removing %d with bucket %zd\n", key, b);



    for (size_t o = 0; o < y->size; o++) {

        size_t i = (b + o) & y->mask;  // wrap as necessary

        int bv = y->buckets[i];

        LOG(" -- b %d: %d\n", i, bv);

        LOG(" -- b %zd: %d\n", i, bv);

        if (bv == key) {

            if (y->buckets[(i + 1) & y->mask] == YACHT_NO_KEY) {

                y->buckets[i] = YACHT_NO_KEY;