[PATCH v6 6/6] stdlib: Add more qsort{_r} coverage
Noah Goldstein
goldstein.w.n@gmail.com
Tue Aug 29 07:57:41 GMT 2023
On Tue, Jul 18, 2023 at 9:17 AM Adhemerval Zanella via Libc-alpha
<libc-alpha@sourceware.org> wrote:
>
> This patch adds a qsort and qsort_r to trigger the worst case
> scenario for the quicksort (which glibc current lacks coverage).
> The test is done with random input, dfferent internal types (uint8_t,
> uint16_t, uint32_t, uint64_t, large size), and with
> different set of element numbers (from 0 to 17384).
>
> Checked on x86_64-linux-gnu and i686-linux-gnu.
> ---
> stdlib/Makefile | 1 +
> stdlib/tst-qsort3.c | 298 ++++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 299 insertions(+)
> create mode 100644 stdlib/tst-qsort3.c
>
> diff --git a/stdlib/Makefile b/stdlib/Makefile
> index 095518eef4..6af606136e 100644
> --- a/stdlib/Makefile
> +++ b/stdlib/Makefile
> @@ -214,6 +214,7 @@ tests := \
> tst-on_exit \
> tst-qsort \
> tst-qsort2 \
> + tst-qsort3 \
> tst-quick_exit \
> tst-rand48 \
> tst-rand48-2 \
> diff --git a/stdlib/tst-qsort3.c b/stdlib/tst-qsort3.c
> new file mode 100644
> index 0000000000..6940540289
> --- /dev/null
> +++ b/stdlib/tst-qsort3.c
> @@ -0,0 +1,298 @@
> +/* qsort(_r) tests to trigger worst case for quicksort.
> + Copyright (C) 2023 Free Software Foundation, Inc.
> + This file is part of the GNU C Library.
> +
> + The GNU C Library is free software; you can redistribute it and/or
> + modify it under the terms of the GNU Lesser General Public
> + License as published by the Free Software Foundation; either
> + version 2.1 of the License, or (at your option) any later version.
> +
> + The GNU C Library is distributed in the hope that it will be useful,
> + but WITHOUT ANY WARRANTY; without even the implied warranty of
> + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> + Lesser General Public License for more details.
> +
> + You should have received a copy of the GNU Lesser General Public
> + License along with the GNU C Library; if not, see
> + <http://www.gnu.org/licenses/>. */
> +
> +#include <array_length.h>
> +#include <errno.h>
> +#include <getopt.h>
> +#include <stdbool.h>
> +#include <stdint.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <support/check.h>
> +#include <support/support.h>
> +#include <support/test-driver.h>
> +
> +typedef enum
> +{
> + Sorted,
> + Random,
> + Repeated,
> + Bitonic
> +} arraytype_t;
> +
> +/* Ratio of total of elements which will be repeated. */
> +static const double RepeatedRatio = 0.2;
> +
> +struct array_t
> +{
> + arraytype_t type;
> + const char *name;
> +} static const arraytypes[] =
> +{
> + { Sorted, "Sorted" },
> + { Random, "Random" },
> + { Repeated, "Repeated" },
> + { Bitonic, "Bitonic" },
> +};
> +
> +/* Return the index of BASE as interpreted as an array of elements
> + of size SIZE. */
> +static inline void *
> +arr (void *base, size_t idx, size_t size)
> +{
> + return (void*)((uintptr_t)base + (idx * size));
> +}
> +
> +/* Functions used to check qsort. */
> +static int
> +uint8_t_cmp (const void *a, const void *b)
> +{
> + uint8_t ia = *(uint8_t*)a;
> + uint8_t ib = *(uint8_t*)b;
> + return (ia > ib) - (ia < ib);
> +}
> +
> +static int
> +uint16_t_cmp (const void *a, const void *b)
> +{
> + uint16_t ia = *(uint16_t*)a;
> + uint16_t ib = *(uint16_t*)b;
> + return (ia > ib) - (ia < ib);
> +}
> +
> +static int
> +uint32_t_cmp (const void *a, const void *b)
> +{
> + uint32_t ia = *(uint32_t*)a;
> + uint32_t ib = *(uint32_t*)b;
> + return (ia > ib) - (ia < ib);
> +}
> +
> +static int
> +uint64_t_cmp (const void *a, const void *b)
> +{
> + uint64_t ia = *(uint64_t*)a;
> + uint64_t ib = *(uint64_t*)b;
> + return (ia > ib) - (ia < ib);
> +}
> +
> +#define LARGE_SIZE 48
> +
Would personally make this 47 so it doesn't use
the 8-byte/4-byte optimized swap (which are also covered).
> +static int
> +large_cmp (const void *a, const void *b)
> +{
> + return memcmp (a, b, LARGE_SIZE);
> +}
> +
> +/* Function used to check qsort_r. */
> +typedef enum
> +{
> + UINT8_CMP_T,
> + UINT16_CMP_T,
> + UINT32_CMP_T,
> + UINT64_CMP_T,
> + LARGE_CMP_T
> +} type_cmp_t;
> +
> +static type_cmp_t
> +uint_t_cmp_type (size_t sz)
> +{
> + switch (sz)
> + {
> + case sizeof (uint8_t): return UINT8_CMP_T;
> + case sizeof (uint16_t): return UINT16_CMP_T;
> + case sizeof (uint64_t): return UINT64_CMP_T;
> + case sizeof (uint32_t): return UINT32_CMP_T;
> + default: return LARGE_CMP_T;
> + }
> +}
> +
> +static int
> +uint_t_cmp (const void *a, const void *b, void *arg)
> +{
> + type_cmp_t type = *(type_cmp_t*) arg;
> + switch (type)
> + {
> + case UINT8_CMP_T: return uint8_t_cmp (a, b);
> + case UINT32_CMP_T: return uint32_t_cmp (a, b);
> + case UINT16_CMP_T: return uint16_t_cmp (a, b);
> + case UINT64_CMP_T: return uint64_t_cmp (a, b);
> + default: return large_cmp (a, b);
> + }
> +}
> +
> +static void
> +seq (void *elem, size_t type_size, int value)
> +{
> + if (type_size == sizeof (uint8_t))
> + *(uint8_t*)elem = value;
> + else if (type_size == sizeof (uint16_t))
> + *(uint16_t*)elem = value;
> + else if (type_size == sizeof (uint32_t))
> + *(uint32_t*)elem = value;
> + else if (type_size == sizeof (uint64_t))
> + *(uint64_t*)elem = value;
> + else
> + memset (elem, value, type_size);
> +}
> +
> +static void *
> +create_array (size_t nmemb, size_t type_size, arraytype_t type)
> +{
> + size_t size = nmemb * type_size;
> + void *array = xmalloc (size);
> +
> + switch (type)
> + {
> + case Sorted:
> + for (size_t i = 0; i < nmemb; i++)
> + seq (arr (array, i, type_size), type_size, i);
> + break;
> +
> + case Random:
> + arc4random_buf (array, size);
> + break;
> +
> + case Repeated:
> + {
> + arc4random_buf (array, size);
> +
> + void *randelem = xmalloc (type_size);
> + arc4random_buf (randelem, type_size);
> +
> + /* Repeat REPEATED elements (based on RepeatRatio ratio) in the random
> + array. */
> + size_t repeated = (size_t)(nmemb * RepeatedRatio);
> + for (size_t i = 0; i < repeated; i++)
> + {
> + size_t pos = arc4random_uniform (nmemb - 1);
> + memcpy (arr (array, pos, type_size), randelem, type_size);
> + }
> + free (randelem);
> + }
> + break;
> +
> + case Bitonic:
> + {
> + size_t i;
> + for (i = 0; i < nmemb / 2; i++)
> + seq (arr (array, i, type_size), type_size, i);
> + for ( ; i < nmemb; i++)
> + seq (arr (array, i, type_size), type_size, (nmemb - 1) - i);
> + }
> + break;
> + }
Would add random 0s/1s case.
> +
> + return array;
> +}
> +
> +typedef int (*cmpfunc_t)(const void *, const void *);
> +
> +/* Check if ARRAY of total NMEMB element of size SIZE is sorted
> + based on CMPFUNC. */
> +static void
> +check_array (void *array, size_t nmemb, size_t type_size,
> + cmpfunc_t cmpfunc)
> +{
> + for (size_t i = 1; i < nmemb; i++)
> + {
> + int ret = cmpfunc (arr (array, i, type_size),
> + arr (array, i-1, type_size));
> + TEST_VERIFY_EXIT (ret >= 0);
> + }
This doesn't cover something like overwriting elements.
Think test generation should be done in a way s.t it also generates
a complete reference array.
For the random tests can do something like:
```
arr[0] = 0;
for(i =1; i < nelem; ++i) {
if(arc4random() % 100 < dup_percentage) {
memcpy(arr + i, arr + i -1, elem_size);
}
else {
arr[i] = arr[i - 1] + 1;
}
}
memcpy(ref_arr, arr, nelem * elem_size);
for(i = 0; i < nelem; ++i) {
swap(arr[arc4rand() % nelem], arr[arc4rand() % nelem]);
}
```
for the rest of the patterns think its easy enough to generate sorted
reference at the same time.
> +}
> +
> +static void
> +check_qsort (size_t nelem, size_t type_size, arraytype_t type,
> + cmpfunc_t cmpfunc)
> +{
> + void *array = create_array (nelem, type_size, type);
> +
> + qsort (array, nelem, type_size, cmpfunc);
> +
> + check_array (array, nelem, type_size, cmpfunc);
> +
> + free (array);
Just allocate max arr size at begining and reuse it to speed up tests?
> +}
> +
> +static void
> +check_qsort_r (size_t nelem, size_t type_size, arraytype_t type,
> + cmpfunc_t cmpfunc)
> +{
> + void *array = create_array (nelem, type_size, type);
> +
> + type_cmp_t typecmp = uint_t_cmp_type (type_size);
> + qsort_r (array, nelem, type_size, uint_t_cmp, &typecmp);
> +
> + check_array (array, nelem, type_size, cmpfunc);
> +
> + free (array);
> +}
> +
> +static int
> +do_test (void)
> +{
> + /* Some random sizes. */
> + const size_t nelems[] = { 0, 1, 7, 20, 32, 100, 256, 1024, 8560, 17384 };
> +
> + struct test_t
> + {
> + size_t type_size;
> + cmpfunc_t cmpfunc;
> + }
> + const tests[] =
> + {
> + { sizeof (uint8_t), uint8_t_cmp },
> + { sizeof (uint16_t), uint16_t_cmp },
> + { sizeof (uint32_t), uint32_t_cmp },
> + { sizeof (uint64_t), uint64_t_cmp },
> + /* Test swap with large elements. */
> + { LARGE_SIZE, large_cmp },
> + };
> +
> + for (const struct test_t *test = tests; test < array_end (tests); ++test)
> + {
> + if (test_verbose > 0)
> + printf ("info: testing qsort with type_size=%zu\n", test->type_size);
> + for (const struct array_t *arraytype = arraytypes;
> + arraytype < array_end (arraytypes);
> + ++arraytype)
> + {
> + if (test_verbose > 0)
> + printf (" distribution=%s\n", arraytype->name);
> + for (const size_t *nelem = nelems;
> + nelem < array_end (nelems);
> + ++nelem)
> + {
> + if (test_verbose > 0)
> + printf (" i nelem=%zu, total size=%zu\n", *nelem,
> + *nelem * test->type_size);
> +
> + check_qsort (*nelem, test->type_size, arraytype->type,
> + test->cmpfunc);
> + check_qsort_r (*nelem, test->type_size, arraytype->type,
> + test->cmpfunc);
> + }
> + }
> + }
> +
> + return 0;
> +}
> +
> +#include <support/test-driver.c>
> --
> 2.34.1
>
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