From ddb8dc4ad0523e07ab0475d6c9583d8ca27de8dc Mon Sep 17 00:00:00 2001 From: David Goldblatt Date: Mon, 27 Jul 2020 12:26:06 -0700 Subject: [PATCH] FB: Add range iteration support. --- include/jemalloc/internal/flat_bitmap.h | 65 +++++++ test/unit/flat_bitmap.c | 234 +++++++++++++++++++++++- 2 files changed, 298 insertions(+), 1 deletion(-) diff --git a/include/jemalloc/internal/flat_bitmap.h b/include/jemalloc/internal/flat_bitmap.h index cf2baab0..7b894d53 100644 --- a/include/jemalloc/internal/flat_bitmap.h +++ b/include/jemalloc/internal/flat_bitmap.h @@ -219,4 +219,69 @@ fb_fls(fb_group_t *fb, size_t nbits, size_t max_bit) { /* forward */ false); } +/* Returns whether or not we found a range. */ +JEMALLOC_ALWAYS_INLINE bool +fb_iter_range_impl(fb_group_t *fb, size_t nbits, size_t start, size_t *r_begin, + size_t *r_len, bool val, bool forward) { + assert(start < nbits); + ssize_t next_range_begin = fb_find_impl(fb, nbits, start, val, forward); + if ((forward && next_range_begin == (ssize_t)nbits) + || (!forward && next_range_begin == (ssize_t)-1)) { + return false; + } + /* Half open range; the set bits are [begin, end). */ + ssize_t next_range_end = fb_find_impl(fb, nbits, next_range_begin, !val, + forward); + if (forward) { + *r_begin = next_range_begin; + *r_len = next_range_end - next_range_begin; + } else { + *r_begin = next_range_end + 1; + *r_len = next_range_begin - next_range_end; + } + return true; +} + +/* + * Used to iterate through ranges of set bits. + * + * Tries to find the next contiguous sequence of set bits with a first index >= + * start. If one exists, puts the earliest bit of the range in *r_begin, its + * length in *r_len, and returns true. Otherwise, returns false (without + * touching *r_begin or *r_end). + */ +static inline bool +fb_srange_iter(fb_group_t *fb, size_t nbits, size_t start, size_t *r_begin, + size_t *r_len) { + return fb_iter_range_impl(fb, nbits, start, r_begin, r_len, + /* val */ true, /* forward */ true); +} + +/* + * The same as fb_srange_iter, but searches backwards from start rather than + * forwards. (The position returned is still the earliest bit in the range). + */ +static inline bool +fb_srange_riter(fb_group_t *fb, size_t nbits, size_t start, size_t *r_begin, + size_t *r_len) { + return fb_iter_range_impl(fb, nbits, start, r_begin, r_len, + /* val */ true, /* forward */ false); +} + +/* Similar to fb_srange_iter, but searches for unset bits. */ +static inline bool +fb_urange_iter(fb_group_t *fb, size_t nbits, size_t start, size_t *r_begin, + size_t *r_len) { + return fb_iter_range_impl(fb, nbits, start, r_begin, r_len, + /* val */ false, /* forward */ true); +} + +/* Similar to fb_srange_riter, but searches for unset bits. */ +static inline bool +fb_urange_riter(fb_group_t *fb, size_t nbits, size_t start, size_t *r_begin, + size_t *r_len) { + return fb_iter_range_impl(fb, nbits, start, r_begin, r_len, + /* val */ false, /* forward */ false); +} + #endif /* JEMALLOC_INTERNAL_FB_H */ diff --git a/test/unit/flat_bitmap.c b/test/unit/flat_bitmap.c index 1667f777..14ac6ba4 100644 --- a/test/unit/flat_bitmap.c +++ b/test/unit/flat_bitmap.c @@ -301,6 +301,236 @@ TEST_BEGIN(test_empty_full) { } TEST_END +TEST_BEGIN(test_iter_range_simple) { + size_t set_limit = 30; + size_t nbits = 100; + fb_group_t fb[FB_NGROUPS(100)]; + + fb_init(fb, nbits); + + /* + * Failing to initialize these can lead to build failures with -Wall; + * the compiler can't prove that they're set. + */ + size_t begin = (size_t)-1; + size_t len = (size_t)-1; + bool result; + + /* A set of checks with only the first set_limit bits *set*. */ + fb_set_range(fb, nbits, 0, set_limit); + for (size_t i = 0; i < set_limit; i++) { + result = fb_srange_iter(fb, nbits, i, &begin, &len); + expect_true(result, "Should have found a range at %zu", i); + expect_zu_eq(i, begin, "Incorrect begin at %zu", i); + expect_zu_eq(set_limit - i, len, "Incorrect len at %zu", i); + + result = fb_urange_iter(fb, nbits, i, &begin, &len); + expect_true(result, "Should have found a range at %zu", i); + expect_zu_eq(set_limit, begin, "Incorrect begin at %zu", i); + expect_zu_eq(nbits - set_limit, len, "Incorrect len at %zu", i); + + result = fb_srange_riter(fb, nbits, i, &begin, &len); + expect_true(result, "Should have found a range at %zu", i); + expect_zu_eq(0, begin, "Incorrect begin at %zu", i); + expect_zu_eq(i + 1, len, "Incorrect len at %zu", i); + + result = fb_urange_riter(fb, nbits, i, &begin, &len); + expect_false(result, "Should not have found a range at %zu", i); + } + for (size_t i = set_limit; i < nbits; i++) { + result = fb_srange_iter(fb, nbits, i, &begin, &len); + expect_false(result, "Should not have found a range at %zu", i); + + result = fb_urange_iter(fb, nbits, i, &begin, &len); + expect_true(result, "Should have found a range at %zu", i); + expect_zu_eq(i, begin, "Incorrect begin at %zu", i); + expect_zu_eq(nbits - i, len, "Incorrect len at %zu", i); + + result = fb_srange_riter(fb, nbits, i, &begin, &len); + expect_true(result, "Should have found a range at %zu", i); + expect_zu_eq(0, begin, "Incorrect begin at %zu", i); + expect_zu_eq(set_limit, len, "Incorrect len at %zu", i); + + result = fb_urange_riter(fb, nbits, i, &begin, &len); + expect_true(result, "Should have found a range at %zu", i); + expect_zu_eq(set_limit, begin, "Incorrect begin at %zu", i); + expect_zu_eq(i - set_limit + 1, len, "Incorrect len at %zu", i); + } + + /* A set of checks with only the first set_limit bits *unset*. */ + fb_unset_range(fb, nbits, 0, set_limit); + fb_set_range(fb, nbits, set_limit, nbits - set_limit); + for (size_t i = 0; i < set_limit; i++) { + result = fb_srange_iter(fb, nbits, i, &begin, &len); + expect_true(result, "Should have found a range at %zu", i); + expect_zu_eq(set_limit, begin, "Incorrect begin at %zu", i); + expect_zu_eq(nbits - set_limit, len, "Incorrect len at %zu", i); + + result = fb_urange_iter(fb, nbits, i, &begin, &len); + expect_true(result, "Should have found a range at %zu", i); + expect_zu_eq(i, begin, "Incorrect begin at %zu", i); + expect_zu_eq(set_limit - i, len, "Incorrect len at %zu", i); + + result = fb_srange_riter(fb, nbits, i, &begin, &len); + expect_false(result, "Should not have found a range at %zu", i); + + result = fb_urange_riter(fb, nbits, i, &begin, &len); + expect_true(result, "Should not have found a range at %zu", i); + expect_zu_eq(0, begin, "Incorrect begin at %zu", i); + expect_zu_eq(i + 1, len, "Incorrect len at %zu", i); + } + for (size_t i = set_limit; i < nbits; i++) { + result = fb_srange_iter(fb, nbits, i, &begin, &len); + expect_true(result, "Should have found a range at %zu", i); + expect_zu_eq(i, begin, "Incorrect begin at %zu", i); + expect_zu_eq(nbits - i, len, "Incorrect len at %zu", i); + + result = fb_urange_iter(fb, nbits, i, &begin, &len); + expect_false(result, "Should not have found a range at %zu", i); + + result = fb_srange_riter(fb, nbits, i, &begin, &len); + expect_true(result, "Should have found a range at %zu", i); + expect_zu_eq(set_limit, begin, "Incorrect begin at %zu", i); + expect_zu_eq(i - set_limit + 1, len, "Incorrect len at %zu", i); + + result = fb_urange_riter(fb, nbits, i, &begin, &len); + expect_true(result, "Should have found a range at %zu", i); + expect_zu_eq(0, begin, "Incorrect begin at %zu", i); + expect_zu_eq(set_limit, len, "Incorrect len at %zu", i); + } + +} +TEST_END + +/* + * Doing this bit-by-bit is too slow for a real implementation, but for testing + * code, it's easy to get right. In the exhaustive tests, we'll compare the + * (fast but tricky) real implementation against the (slow but simple) testing + * one. + */ +static bool +fb_iter_simple(fb_group_t *fb, size_t nbits, size_t start, size_t *r_begin, + size_t *r_len, bool val, bool forward) { + ssize_t stride = (forward ? (ssize_t)1 : (ssize_t)-1); + ssize_t range_begin = (ssize_t)start; + for (; range_begin != (ssize_t)nbits && range_begin != -1; + range_begin += stride) { + if (fb_get(fb, nbits, range_begin) == val) { + ssize_t range_end = range_begin; + for (; range_end != (ssize_t)nbits && range_end != -1; + range_end += stride) { + if (fb_get(fb, nbits, range_end) != val) { + break; + } + } + if (forward) { + *r_begin = range_begin; + *r_len = range_end - range_begin; + } else { + *r_begin = range_end + 1; + *r_len = range_begin - range_end; + } + return true; + } + } + return false; +} + +static void +expect_iter_results_at(fb_group_t *fb, size_t nbits, size_t pos, + bool val, bool forward) { + bool iter_res; + size_t iter_begin; + size_t iter_len; + if (val) { + if (forward) { + iter_res = fb_srange_iter(fb, nbits, pos, + &iter_begin, &iter_len); + } else { + iter_res = fb_srange_riter(fb, nbits, pos, + &iter_begin, &iter_len); + } + } else { + if (forward) { + iter_res = fb_urange_iter(fb, nbits, pos, + &iter_begin, &iter_len); + } else { + iter_res = fb_urange_riter(fb, nbits, pos, + &iter_begin, &iter_len); + } + } + + bool simple_iter_res; + size_t simple_iter_begin; + size_t simple_iter_len; + simple_iter_res = fb_iter_simple(fb, nbits, pos, &simple_iter_begin, + &simple_iter_len, val, forward); + + expect_b_eq(iter_res, simple_iter_res, "Result mismatch at %zu", pos); + if (iter_res && simple_iter_res) { + assert_zu_eq(iter_begin, simple_iter_begin, + "Begin mismatch at %zu", pos); + expect_zu_eq(iter_len, simple_iter_len, + "Length mismatch at %zu", pos); + } +} + +static void +expect_iter_results(fb_group_t *fb, size_t nbits) { + for (size_t i = 0; i < nbits; i++) { + expect_iter_results_at(fb, nbits, i, false, false); + expect_iter_results_at(fb, nbits, i, false, true); + expect_iter_results_at(fb, nbits, i, true, false); + expect_iter_results_at(fb, nbits, i, true, true); + } +} + +static void +set_pattern_3(fb_group_t *fb, size_t nbits, bool zero_val) { + for (size_t i = 0; i < nbits; i++) { + if ((i % 6 < 3 && zero_val) || (i % 6 >= 3 && !zero_val)) { + fb_set(fb, nbits, i); + } else { + fb_unset(fb, nbits, i); + } + } +} + +static void +do_test_iter_range_exhaustive(size_t nbits) { + /* This test is also pretty slow. */ + if (nbits > 1000) { + return; + } + size_t sz = FB_NGROUPS(nbits) * sizeof(fb_group_t); + fb_group_t *fb = malloc(sz); + fb_init(fb, nbits); + + set_pattern_3(fb, nbits, /* zero_val */ true); + expect_iter_results(fb, nbits); + + set_pattern_3(fb, nbits, /* zero_val */ false); + expect_iter_results(fb, nbits); + + fb_set_range(fb, nbits, 0, nbits); + fb_unset_range(fb, nbits, 0, nbits / 2 == 0 ? 1 : nbits / 2); + expect_iter_results(fb, nbits); + + fb_unset_range(fb, nbits, 0, nbits); + fb_set_range(fb, nbits, 0, nbits / 2 == 0 ? 1: nbits / 2); + expect_iter_results(fb, nbits); + + free(fb); +} + +TEST_BEGIN(test_iter_range_exhaustive) { +#define NB(nbits) \ + do_test_iter_range_exhaustive(nbits); + NBITS_TAB +#undef NB +} +TEST_END + int main(void) { return test_no_reentrancy( @@ -309,5 +539,7 @@ main(void) { test_search_simple, test_search_exhaustive, test_range_simple, - test_empty_full); + test_empty_full, + test_iter_range_simple, + test_iter_range_exhaustive); }