Quoting Michael Niedermayer (2022-01-25 11:21:08)
> This decreases the quality of the seeds during the test, it does not affect
> the seeds outside the test.
> There is a small chance that this causes test failures, if that happens
> the threshold needs adjusting
>
> Testing on an idle x86_64 system shows that this passes even with the test
> strength
> increased to 32768 from 256 with 0 retries
> So test failures are not anticipated
> Lowering the threshold from 3 to 2 causes failure at test strength of 32768
>
> Signed-off-by: Michael Niedermayer <mich...@niedermayer.cc>
> ---
> libavutil/random_seed.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/libavutil/random_seed.c b/libavutil/random_seed.c
> index 70dc509d2f..509b74936c 100644
> --- a/libavutil/random_seed.c
> +++ b/libavutil/random_seed.c
> @@ -95,7 +95,7 @@ static uint32_t get_generic_seed(void)
> last_td = t - last_t;
> buffer[++i & 511] += last_td % 3294638521U;
> if ((t - init_t) >= CLOCKS_PER_SEC>>5)
> - if (last_i && i - last_i > 4 || i - last_i > 64 || TEST && i
> - last_i > 8)
> + if (last_i && i - last_i > 4 || i - last_i > 64 || TEST && i
> - last_i > 3)
On my Ryzen 5950x, this brings the test runtime from > 60s to ~30s,
which is a good improvement, but still quite a lot (the entire FATE run
with -j32 and without the random-seed test is ~40s).
How about something like this instead (takes about 8s on my machines, observed
no test failures):
diff --git a/libavutil/random_seed.c b/libavutil/random_seed.c
index 70dc509d2f..b006a75c39 100644
--- a/libavutil/random_seed.c
+++ b/libavutil/random_seed.c
@@ -73,6 +73,7 @@ static uint32_t get_generic_seed(void)
static uint32_t buffer[512] = { 0 };
unsigned char digest[20];
uint64_t last_i = i;
+ uint64_t cnt = 0;
av_assert0(sizeof(tmp) >= av_sha_size);
@@ -88,9 +89,11 @@ static uint32_t get_generic_seed(void)
for (;;) {
clock_t t = clock();
- if (last_t + 2*last_td + (CLOCKS_PER_SEC > 1000) >= t) {
+ if (last_t + 2*last_td + (CLOCKS_PER_SEC > 1000) >= t &&
+ !(TEST && cnt > (1 << 15))) {
last_td = t - last_t;
buffer[i & 511] = 1664525*buffer[i & 511] + 1013904223 + (last_td
% 3294638521U);
+ cnt++;
} else {
last_td = t - last_t;
buffer[++i & 511] += last_td % 3294638521U;
--
Anton Khirnov
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