| Message ID | CAN8TOE-zTCY-SRrVpsFExu32yq_3j7FJGgVUBN3CEt_E_qzS8Q@mail.gmail.com |
|---|---|
| State | New, archived |
| Headers | show |
Am Mittwoch, den 30.11.2011, 10:24 -0800 schrieb Brian Norris: > On Mon, Nov 28, 2011 at 11:30 PM, Jan Weitzel <J.Weitzel@phytec.de> wrote: > > Brian Norris <computersforpeace@gmail.com> schrieb am 28.11.2011 19:11:52: > >> + if (seed < 0) > >> + seed = time(NULL); > >> + srand(seed); > > > > So you loose all negative seeds. > > Well, srand() technically takes unsigned ints, so all seeds are > technically positive. But that just means we're parsing and storing > seeds wrong (not a big deal, really). > > > What is about > > > > int seed = time(NULL); > > ... > > case 's' > > seed = atol(optarg); > > ... > > } > > srand(seed); > > Not sure if I understand the question perfectly (clarify if I'm > wrong). My patch was intended to: > (1) use the user-supplied seed (--seed=X) if supplied > (2) use a random seed (based on time()) if the seed is left > uninitialized (i.e., -1) > > Anyway, I see a problem with my method. How about the following patch, > which saves the time first, then overwrites it with the supplied seed > if provided. Acked-by: Jan Weitzel <j.weitzel@phytec.de> Maybe you need to rebase it, because my former patch just got pushed. > From 4df0643c4819f5de5db54b855406852da0dc6bf1 Mon Sep 17 00:00:00 2001 > From: Brian Norris <computersforpeace@gmail.com> > Date: Mon, 28 Nov 2011 10:03:30 -0800 > Subject: [PATCH] nandtest: seed random generator properly > > This patch fixes two problems in nandtest: > > * if a seed is provided it is actually not used. First call is > "seed = rand()" killing the given seed. > Credit: Jan Weitzel <j.weitzel@phytec.de> > > * if a seed is not provided, we use the default rand() values, which > produces the same sequence of values every run.r > > To solve these problems, we seed the random number generator with either > the time() or the supplied seed. > > Cc: Jan Weitzel <j.weitzel@phytec.de> > Signed-off-by: Brian Norris <computersforpeace@gmail.com> > --- > nandtest.c | 4 ++++ > 1 files changed, 4 insertions(+), 0 deletions(-) > > diff --git a/nandtest.c b/nandtest.c > index dc28d09..7811be2 100644 > --- a/nandtest.c > +++ b/nandtest.c > @@ -140,6 +140,8 @@ int main(int argc, char **argv) > uint32_t offset = 0; > uint32_t length = -1; > > + seed = time(NULL); > + > for (;;) { > static const char *short_options="hkl:mo:p:s:"; > static const struct option long_options[] = { > @@ -243,6 +245,8 @@ int main(int argc, char **argv) > printf("Bad blocks : %d\n", oldstats.badblocks); > printf("BBT blocks : %d\n", oldstats.bbtblocks); > > + srand(seed); > + > for (pass = 0; pass < nr_passes; pass++) { > loff_t test_ofs; >
On Wed, 2011-11-30 at 10:24 -0800, Brian Norris wrote: > On Mon, Nov 28, 2011 at 11:30 PM, Jan Weitzel <J.Weitzel@phytec.de> wrote: > > Brian Norris <computersforpeace@gmail.com> schrieb am 28.11.2011 19:11:52: > >> + if (seed < 0) > >> + seed = time(NULL); > >> + srand(seed); > > > > So you loose all negative seeds. > > Well, srand() technically takes unsigned ints, so all seeds are > technically positive. But that just means we're parsing and storing > seeds wrong (not a big deal, really). Brian, would you please send an incremental patch on top of Jan's which I've pushed? Artem.
diff --git a/nandtest.c b/nandtest.c index dc28d09..7811be2 100644 --- a/nandtest.c +++ b/nandtest.c @@ -140,6 +140,8 @@ int main(int argc, char **argv) uint32_t offset = 0; uint32_t length = -1; + seed = time(NULL); + for (;;) { static const char *short_options="hkl:mo:p:s:"; static const struct option long_options[] = { @@ -243,6 +245,8 @@ int main(int argc, char **argv) printf("Bad blocks : %d\n", oldstats.badblocks); printf("BBT blocks : %d\n", oldstats.bbtblocks); + srand(seed); + for (pass = 0; pass < nr_passes; pass++) { loff_t test_ofs;