* [PATCH] benchtests: Add difficult strstr needle for bruteforce algorithms
@ 2024-04-18 13:03 Wilco Dijkstra
2024-04-23 18:47 ` Adhemerval Zanella Netto
0 siblings, 1 reply; 2+ messages in thread
From: Wilco Dijkstra @ 2024-04-18 13:03 UTC (permalink / raw)
To: 'GNU C Library'
Add another difficult needle to strstr that clearly shows the quadratic
complexity of bruteforce algorithms.
OK for commit?
---
diff --git a/benchtests/bench-strstr.c b/benchtests/bench-strstr.c
index 9288ad16e963d5397419aa11263520d259d2d6b9..4b07d39a50b0e5e1f29743a258b05466099c1959 100644
--- a/benchtests/bench-strstr.c
+++ b/benchtests/bench-strstr.c
@@ -352,6 +352,33 @@ test_hard_needle (json_ctx_t *json_ctx, size_t ne_len, size_t hs_len)
json_array_end (json_ctx);
json_element_object_end (json_ctx);
}
+
+ /* Hard needle for bruteforce algorithms that match first few chars. */
+ {
+ memset (hs, 'a', hs_len);
+ for (int i = ne_len-1; i < hs_len; i += ne_len)
+ hs[i] = 'b';
+ hs[hs_len] = 0;
+
+ memset (ne, 'a', ne_len);
+ ne[ne_len] = 0;
+
+ json_element_object_begin (json_ctx);
+ json_attr_uint (json_ctx, "len_haystack", hs_len);
+ json_attr_uint (json_ctx, "len_needle", ne_len);
+ json_attr_uint (json_ctx, "align_haystack", 0);
+ json_attr_uint (json_ctx, "align_needle", 0);
+ json_attr_uint (json_ctx, "fail", 1);
+ json_attr_string (json_ctx, "desc", "Difficult bruteforce needle");
+
+ json_array_begin (json_ctx, "timings");
+
+ FOR_EACH_IMPL (impl, 0)
+ do_one_test (json_ctx, impl, hs, ne, NULL);
+
+ json_array_end (json_ctx);
+ json_element_object_end (json_ctx);
+ }
}
static int
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [PATCH] benchtests: Add difficult strstr needle for bruteforce algorithms
2024-04-18 13:03 [PATCH] benchtests: Add difficult strstr needle for bruteforce algorithms Wilco Dijkstra
@ 2024-04-23 18:47 ` Adhemerval Zanella Netto
0 siblings, 0 replies; 2+ messages in thread
From: Adhemerval Zanella Netto @ 2024-04-23 18:47 UTC (permalink / raw)
To: Wilco Dijkstra, 'GNU C Library'
On 18/04/24 10:03, Wilco Dijkstra wrote:
>
> Add another difficult needle to strstr that clearly shows the quadratic
> complexity of bruteforce algorithms.
>
> OK for commit?
LGTM, thanks.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
>
> ---
>
> diff --git a/benchtests/bench-strstr.c b/benchtests/bench-strstr.c
> index 9288ad16e963d5397419aa11263520d259d2d6b9..4b07d39a50b0e5e1f29743a258b05466099c1959 100644
> --- a/benchtests/bench-strstr.c
> +++ b/benchtests/bench-strstr.c
> @@ -352,6 +352,33 @@ test_hard_needle (json_ctx_t *json_ctx, size_t ne_len, size_t hs_len)
> json_array_end (json_ctx);
> json_element_object_end (json_ctx);
> }
> +
> + /* Hard needle for bruteforce algorithms that match first few chars. */
> + {
> + memset (hs, 'a', hs_len);
> + for (int i = ne_len-1; i < hs_len; i += ne_len)
> + hs[i] = 'b';
> + hs[hs_len] = 0;
> +
> + memset (ne, 'a', ne_len);
> + ne[ne_len] = 0;
> +
> + json_element_object_begin (json_ctx);
> + json_attr_uint (json_ctx, "len_haystack", hs_len);
> + json_attr_uint (json_ctx, "len_needle", ne_len);
> + json_attr_uint (json_ctx, "align_haystack", 0);
> + json_attr_uint (json_ctx, "align_needle", 0);
> + json_attr_uint (json_ctx, "fail", 1);
> + json_attr_string (json_ctx, "desc", "Difficult bruteforce needle");
> +
> + json_array_begin (json_ctx, "timings");
> +
> + FOR_EACH_IMPL (impl, 0)
> + do_one_test (json_ctx, impl, hs, ne, NULL);
> +
> + json_array_end (json_ctx);
> + json_element_object_end (json_ctx);
> + }
> }
>
> static int
>
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