* [igt-dev] [i-g-t] tests/kms_setmode: basic Improve accuracy with using of confidence interval @ 2020-11-02 9:08 Anand Moon 2020-11-03 10:49 ` Chris Wilson 0 siblings, 1 reply; 7+ messages in thread From: Anand Moon @ 2020-11-02 9:08 UTC (permalink / raw) To: igt-dev; +Cc: Anand Moon Using confidence interval formula accuracy is estimates approximately at 95% when {X} is the average of a sample of size n. Use this confidence interval formula as used in statistics to estimate the accuracy. Signed-off-by: Anand Moon <anandx.ram.moon@intel.com> --- See below link. https://en.wikipedia.org/wiki/68%E2%80%9395%E2%80%9399.7_rule#Cumulative_distribution_function --- tests/kms_setmode.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/tests/kms_setmode.c b/tests/kms_setmode.c index 92f3ead2..58814a13 100644 --- a/tests/kms_setmode.c +++ b/tests/kms_setmode.c @@ -494,7 +494,7 @@ static void check_timings(int crtc_idx, const drmModeModeInfo *kmode) * which depend on timing, giving the lowest acceptable MTBF of 5.6s * for 60Hz sampling rate. */ - accuracy = 3. * stddev; + accuracy = 3. * stddev / sqrt(CALIBRATE_TS_STEPS); igt_info("Expected frametime: %.0fus; measured %.1fus +- %.3fus accuracy %.2f%% [%.2f scanlines]\n", expected, mean, stddev, -- 2.25.1 _______________________________________________ igt-dev mailing list igt-dev@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/igt-dev ^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [igt-dev] [i-g-t] tests/kms_setmode: basic Improve accuracy with using of confidence interval 2020-11-02 9:08 [igt-dev] [i-g-t] tests/kms_setmode: basic Improve accuracy with using of confidence interval Anand Moon @ 2020-11-03 10:49 ` Chris Wilson 2020-11-03 17:58 ` Ram Moon, AnandX 0 siblings, 1 reply; 7+ messages in thread From: Chris Wilson @ 2020-11-03 10:49 UTC (permalink / raw) To: Anand Moon, igt-dev; +Cc: Anand Moon Quoting Anand Moon (2020-11-02 09:08:36) > Using confidence interval formula accuracy is estimates approximately > at 95% when {X} is the average of a sample of size n. > Use this confidence interval formula as used in statistics > to estimate the accuracy. > > Signed-off-by: Anand Moon <anandx.ram.moon@intel.com> > --- > See below link. > https://en.wikipedia.org/wiki/68%E2%80%9395%E2%80%9399.7_rule#Cumulative_distribution_function > --- > tests/kms_setmode.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/tests/kms_setmode.c b/tests/kms_setmode.c > index 92f3ead2..58814a13 100644 > --- a/tests/kms_setmode.c > +++ b/tests/kms_setmode.c > @@ -494,7 +494,7 @@ static void check_timings(int crtc_idx, const drmModeModeInfo *kmode) > * which depend on timing, giving the lowest acceptable MTBF of 5.6s > * for 60Hz sampling rate. > */ > - accuracy = 3. * stddev; > + accuracy = 3. * stddev / sqrt(CALIBRATE_TS_STEPS); Oops, yes, this should be standard error rather than deviation. Could you add igt_stats_get_std_error() so we don't hardcode N? -Chris _______________________________________________ igt-dev mailing list igt-dev@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/igt-dev ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [igt-dev] [i-g-t] tests/kms_setmode: basic Improve accuracy with using of confidence interval 2020-11-03 10:49 ` Chris Wilson @ 2020-11-03 17:58 ` Ram Moon, AnandX 2020-11-20 9:12 ` Ram Moon, AnandX 0 siblings, 1 reply; 7+ messages in thread From: Ram Moon, AnandX @ 2020-11-03 17:58 UTC (permalink / raw) To: Chris Wilson, igt-dev Hi Chris, Thanks for your review comment. -----Original Message----- From: Chris Wilson <chris@chris-wilson.co.uk> Sent: Tuesday, November 3, 2020 4:19 PM To: Ram Moon, AnandX <anandx.ram.moon@intel.com>; igt-dev@lists.freedesktop.org Cc: Ram Moon, AnandX <anandx.ram.moon@intel.com> Subject: Re: [igt-dev] [i-g-t] tests/kms_setmode: basic Improve accuracy with using of confidence interval Quoting Anand Moon (2020-11-02 09:08:36) > Using confidence interval formula accuracy is estimates approximately > at 95% when {X} is the average of a sample of size n. > Use this confidence interval formula as used in statistics to estimate > the accuracy. > > Signed-off-by: Anand Moon <anandx.ram.moon@intel.com> > --- > See below link. > https://en.wikipedia.org/wiki/68%E2%80%9395%E2%80%9399.7_rule#Cumulati > ve_distribution_function > --- > tests/kms_setmode.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/tests/kms_setmode.c b/tests/kms_setmode.c index > 92f3ead2..58814a13 100644 > --- a/tests/kms_setmode.c > +++ b/tests/kms_setmode.c > @@ -494,7 +494,7 @@ static void check_timings(int crtc_idx, const drmModeModeInfo *kmode) > * which depend on timing, giving the lowest acceptable MTBF of 5.6s > * for 60Hz sampling rate. > */ > - accuracy = 3. * stddev; > + accuracy = 3. * stddev / sqrt(CALIBRATE_TS_STEPS); Oops, yes, this should be standard error rather than deviation. Could you add igt_stats_get_std_error() so we don't hardcode N? -Chris Do you want me to rename accuracy to std_error and use stats.n_values instead of CALIBRATE_TS_STEPS I could not find the definition of igt_stats_get_std_error function. -Anand _______________________________________________ igt-dev mailing list igt-dev@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/igt-dev ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [igt-dev] [i-g-t] tests/kms_setmode: basic Improve accuracy with using of confidence interval 2020-11-03 17:58 ` Ram Moon, AnandX @ 2020-11-20 9:12 ` Ram Moon, AnandX 2020-11-20 15:05 ` Chris Wilson 0 siblings, 1 reply; 7+ messages in thread From: Ram Moon, AnandX @ 2020-11-20 9:12 UTC (permalink / raw) To: Chris Wilson, igt-dev Hi Chris, -----Original Message----- From: Ram Moon, AnandX Sent: Tuesday, November 3, 2020 11:28 PM To: Chris Wilson <chris@chris-wilson.co.uk>; igt-dev@lists.freedesktop.org Subject: RE: [igt-dev] [i-g-t] tests/kms_setmode: basic Improve accuracy with using of confidence interval Hi Chris, Thanks for your review comment. -----Original Message----- From: Chris Wilson <chris@chris-wilson.co.uk> Sent: Tuesday, November 3, 2020 4:19 PM To: Ram Moon, AnandX <anandx.ram.moon@intel.com>; igt-dev@lists.freedesktop.org Cc: Ram Moon, AnandX <anandx.ram.moon@intel.com> Subject: Re: [igt-dev] [i-g-t] tests/kms_setmode: basic Improve accuracy with using of confidence interval Quoting Anand Moon (2020-11-02 09:08:36) > Using confidence interval formula accuracy is estimates approximately > at 95% when {X} is the average of a sample of size n. > Use this confidence interval formula as used in statistics to estimate > the accuracy. > > Signed-off-by: Anand Moon <anandx.ram.moon@intel.com> > --- > See below link. > https://en.wikipedia.org/wiki/68%E2%80%9395%E2%80%9399.7_rule#Cumulati > ve_distribution_function > --- > tests/kms_setmode.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/tests/kms_setmode.c b/tests/kms_setmode.c index > 92f3ead2..58814a13 100644 > --- a/tests/kms_setmode.c > +++ b/tests/kms_setmode.c > @@ -494,7 +494,7 @@ static void check_timings(int crtc_idx, const drmModeModeInfo *kmode) > * which depend on timing, giving the lowest acceptable MTBF of 5.6s > * for 60Hz sampling rate. > */ > - accuracy = 3. * stddev; > + accuracy = 3. * stddev / sqrt(CALIBRATE_TS_STEPS); Oops, yes, this should be standard error rather than deviation. Could you add igt_stats_get_std_error() so we don't hardcode N? -Chris Do you want me to rename accuracy to std_error and use stats.n_values instead of CALIBRATE_TS_STEPS I could not find the definition of igt_stats_get_std_error function. -Anand Thanks for fixing the code changes. Actually above changes fix the issue to improve the accuracy calculations. But now I am able to reproduce the original bug using 4K monitors on 5.8.x kernel, See below logs. CRTC[98] [Pipe A] Mode: 3840x2160@60Hz Connectors: DP-2[330] Expected frametime: 16668us; measured 16672.3us +- 1.805us accuracy 0.00% [0.07 scanlines] (kms_setmode:14315) CRITICAL: Test assertion failure function check_timings, file ../tests/kms_setmode.c:544: (kms_setmode:14315) CRITICAL: Failed assertion: fabs(mean - expected) < 1.718 * stddev (kms_setmode:14315) CRITICAL: vblank interval differs from modeline! expected 16667.6us, measured 16672us +- 1.805us, difference 4.7us (2.6 sigma) Stack trace: #0 ../lib/igt_core.c:1734 __igt_fail_assert() #1 ../tests/kms_setmode.c:544 test_one_combination() #2 ../tests/kms_setmode.c:834 __real_main883() #3 ../tests/kms_setmode.c:883 main() #4 ../csu/libc-start.c:342 __libc_start_main() #5 [_start+0x2e] Subtest basic failed. **** DEBUG **** So after in digging into the below comments it turns out that *confidence interval* with respect to standard deviation is calculated with *Cumulative distribution function* (formula) As per the Wikipedia table For various values of z, the percentage of values expected to lie in and outside the symmetric interval, CI = (−zσ, zσ), are as follows: [0] https://en.wikipedia.org/wiki/Standard_deviation#Rules_for_normally_distributed_data It turns out that *3 σ* gives around proportion percentage 99.7300204% which is according to the CI = (−zσ, zσ) table. I would like to submit a below patch as this changes fix the overall bug. Please share your thought and suggestion on any alternative approach I should try. Thanks Anand naveen@naveen-GB-Z390-Garuda:~/anand/igt-gpu-tools.internal-rebasing$ git diff diff --git a/tests/kms_setmode.c b/tests/kms_setmode.c index 928a5a8cf..58da36985 100644 --- a/tests/kms_setmode.c +++ b/tests/kms_setmode.c @@ -526,7 +526,7 @@ static void check_timings(int crtc_idx, const drmModeModeInfo *kmode) * See: * https://en.wikipedia.org/wiki/Standard_deviation#Rules_for_normally_distributed_data */ - igt_assert_f(fabs(mean - expected) < 1.718 * stddev, + igt_assert_f(fabs(mean - expected) < 3. * stddev, "vblank interval differs from modeline! expected %.1fus, measured %1.fus +- %.3fus, difference %.1fus (%.1f sigma)\n", expected, mean, stddev, fabs(mean - expected), fabs(mean - expected) / stddev); _______________________________________________ igt-dev mailing list igt-dev@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/igt-dev ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [igt-dev] [i-g-t] tests/kms_setmode: basic Improve accuracy with using of confidence interval 2020-11-20 9:12 ` Ram Moon, AnandX @ 2020-11-20 15:05 ` Chris Wilson 2020-11-23 13:57 ` Ram Moon, AnandX 0 siblings, 1 reply; 7+ messages in thread From: Chris Wilson @ 2020-11-20 15:05 UTC (permalink / raw) To: Ram Moon, AnandX, igt-dev Quoting Ram Moon, AnandX (2020-11-20 09:12:40) > Hi Chris, > > -----Original Message----- > From: Ram Moon, AnandX > Sent: Tuesday, November 3, 2020 11:28 PM > To: Chris Wilson <chris@chris-wilson.co.uk>; igt-dev@lists.freedesktop.org > Subject: RE: [igt-dev] [i-g-t] tests/kms_setmode: basic Improve accuracy with using of confidence interval > > Hi Chris, > > Thanks for your review comment. > > -----Original Message----- > From: Chris Wilson <chris@chris-wilson.co.uk> > Sent: Tuesday, November 3, 2020 4:19 PM > To: Ram Moon, AnandX <anandx.ram.moon@intel.com>; igt-dev@lists.freedesktop.org > Cc: Ram Moon, AnandX <anandx.ram.moon@intel.com> > Subject: Re: [igt-dev] [i-g-t] tests/kms_setmode: basic Improve accuracy with using of confidence interval > > Quoting Anand Moon (2020-11-02 09:08:36) > > Using confidence interval formula accuracy is estimates approximately > > at 95% when {X} is the average of a sample of size n. > > Use this confidence interval formula as used in statistics to estimate > > the accuracy. > > > > Signed-off-by: Anand Moon <anandx.ram.moon@intel.com> > > --- > > See below link. > > https://en.wikipedia.org/wiki/68%E2%80%9395%E2%80%9399.7_rule#Cumulati > > ve_distribution_function > > --- > > tests/kms_setmode.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/tests/kms_setmode.c b/tests/kms_setmode.c index > > 92f3ead2..58814a13 100644 > > --- a/tests/kms_setmode.c > > +++ b/tests/kms_setmode.c > > @@ -494,7 +494,7 @@ static void check_timings(int crtc_idx, const drmModeModeInfo *kmode) > > * which depend on timing, giving the lowest acceptable MTBF of 5.6s > > * for 60Hz sampling rate. > > */ > > - accuracy = 3. * stddev; > > + accuracy = 3. * stddev / sqrt(CALIBRATE_TS_STEPS); > > Oops, yes, this should be standard error rather than deviation. Could you add igt_stats_get_std_error() so we don't hardcode N? > -Chris > > Do you want me to rename accuracy to std_error and use stats.n_values instead of CALIBRATE_TS_STEPS I could not find the definition of igt_stats_get_std_error function. > > -Anand > > Thanks for fixing the code changes. > > Actually above changes fix the issue to improve the accuracy calculations. > But now I am able to reproduce the original bug using 4K monitors on 5.8.x kernel, See below logs. > > CRTC[98] [Pipe A] Mode: 3840x2160@60Hz Connectors: DP-2[330] Expected frametime: 16668us; measured 16672.3us +- 1.805us accuracy 0.00% [0.07 scanlines] > (kms_setmode:14315) CRITICAL: Test assertion failure function check_timings, file ../tests/kms_setmode.c:544: > (kms_setmode:14315) CRITICAL: Failed assertion: fabs(mean - expected) < 1.718 * stddev > (kms_setmode:14315) CRITICAL: vblank interval differs from modeline! expected 16667.6us, measured 16672us +- 1.805us, difference 4.7us (2.6 sigma) Stack trace: > #0 ../lib/igt_core.c:1734 __igt_fail_assert() > #1 ../tests/kms_setmode.c:544 test_one_combination() > #2 ../tests/kms_setmode.c:834 __real_main883() > #3 ../tests/kms_setmode.c:883 main() > #4 ../csu/libc-start.c:342 __libc_start_main() > #5 [_start+0x2e] > Subtest basic failed. > **** DEBUG **** > > So after in digging into the below comments it turns out that *confidence interval* with respect to standard deviation is calculated with *Cumulative distribution function* (formula) > > As per the Wikipedia table > For various values of z, the percentage of values expected to lie in and outside the symmetric interval, CI = (−zσ, zσ), are as follows: > [0] https://en.wikipedia.org/wiki/Standard_deviation#Rules_for_normally_distributed_data > > It turns out that *3 σ* gives around proportion percentage 99.7300204% which is according to the CI = (−zσ, zσ) table. > > I would like to submit a below patch as this changes fix the overall bug. > Please share your thought and suggestion on any alternative approach I should try. You would also have to update the comments as it no longer matches the broaden 90% critical value. Still debating what is a sensible error rate, but in the meantime I would suggest a different approach: ignore the deviation if it is within a single scanline. Something like: - igt_assert_f(fabs(mean - expected) < 1.718 * stddev, - "vblank interval differs from modeline! expected %.1fus, measured %1.fus +- %.3fus, difference %.1fus (%.1f sigma)\n", + igt_assert_f(fabs(mean - expected) < max(line_time(kmode), 1.718 * stddev), + "vblank interval differs from modeline! expected %.1fus, measured %1.fus +- %.3fus, difference %.1fus (%.1f sigma, %.1f scanlines)\n", expected, mean, stddev, - fabs(mean - expected), fabs(mean - expected) / stddev); + fabs(mean - expected), + fabs(mean - expected) / stddev, + fabs(mean - expected) / line_time(kmode)); _______________________________________________ igt-dev mailing list igt-dev@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/igt-dev ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [igt-dev] [i-g-t] tests/kms_setmode: basic Improve accuracy with using of confidence interval 2020-11-20 15:05 ` Chris Wilson @ 2020-11-23 13:57 ` Ram Moon, AnandX 0 siblings, 0 replies; 7+ messages in thread From: Ram Moon, AnandX @ 2020-11-23 13:57 UTC (permalink / raw) To: Chris Wilson, igt-dev Hi Chris, -----Original Message----- From: Chris Wilson <chris@chris-wilson.co.uk> Sent: Friday, November 20, 2020 8:36 PM To: Ram Moon, AnandX <anandx.ram.moon@intel.com>; igt-dev@lists.freedesktop.org Subject: Re: [igt-dev] [i-g-t] tests/kms_setmode: basic Improve accuracy with using of confidence interval Quoting Ram Moon, AnandX (2020-11-20 09:12:40) > Hi Chris, > > -----Original Message----- > From: Ram Moon, AnandX > Sent: Tuesday, November 3, 2020 11:28 PM > To: Chris Wilson <chris@chris-wilson.co.uk>; > igt-dev@lists.freedesktop.org > Subject: RE: [igt-dev] [i-g-t] tests/kms_setmode: basic Improve > accuracy with using of confidence interval > > Hi Chris, > > Thanks for your review comment. > > -----Original Message----- > From: Chris Wilson <chris@chris-wilson.co.uk> > Sent: Tuesday, November 3, 2020 4:19 PM > To: Ram Moon, AnandX <anandx.ram.moon@intel.com>; > igt-dev@lists.freedesktop.org > Cc: Ram Moon, AnandX <anandx.ram.moon@intel.com> > Subject: Re: [igt-dev] [i-g-t] tests/kms_setmode: basic Improve > accuracy with using of confidence interval > > Quoting Anand Moon (2020-11-02 09:08:36) > > Using confidence interval formula accuracy is estimates > > approximately at 95% when {X} is the average of a sample of size n. > > Use this confidence interval formula as used in statistics to > > estimate the accuracy. > > > > Signed-off-by: Anand Moon <anandx.ram.moon@intel.com> > > --- > > See below link. > > https://en.wikipedia.org/wiki/68%E2%80%9395%E2%80%9399.7_rule#Cumula > > ti > > ve_distribution_function > > --- > > tests/kms_setmode.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/tests/kms_setmode.c b/tests/kms_setmode.c index > > 92f3ead2..58814a13 100644 > > --- a/tests/kms_setmode.c > > +++ b/tests/kms_setmode.c > > @@ -494,7 +494,7 @@ static void check_timings(int crtc_idx, const drmModeModeInfo *kmode) > > * which depend on timing, giving the lowest acceptable MTBF of 5.6s > > * for 60Hz sampling rate. > > */ > > - accuracy = 3. * stddev; > > + accuracy = 3. * stddev / sqrt(CALIBRATE_TS_STEPS); > > Oops, yes, this should be standard error rather than deviation. Could you add igt_stats_get_std_error() so we don't hardcode N? > -Chris > > Do you want me to rename accuracy to std_error and use stats.n_values instead of CALIBRATE_TS_STEPS I could not find the definition of igt_stats_get_std_error function. > > -Anand > > Thanks for fixing the code changes. > > Actually above changes fix the issue to improve the accuracy calculations. > But now I am able to reproduce the original bug using 4K monitors on 5.8.x kernel, See below logs. > > CRTC[98] [Pipe A] Mode: 3840x2160@60Hz Connectors: DP-2[330] > Expected frametime: 16668us; measured 16672.3us +- 1.805us accuracy > 0.00% [0.07 scanlines] > (kms_setmode:14315) CRITICAL: Test assertion failure function check_timings, file ../tests/kms_setmode.c:544: > (kms_setmode:14315) CRITICAL: Failed assertion: fabs(mean - expected) > < 1.718 * stddev > (kms_setmode:14315) CRITICAL: vblank interval differs from modeline! expected 16667.6us, measured 16672us +- 1.805us, difference 4.7us (2.6 sigma) Stack trace: > #0 ../lib/igt_core.c:1734 __igt_fail_assert() > #1 ../tests/kms_setmode.c:544 test_one_combination() > #2 ../tests/kms_setmode.c:834 __real_main883() > #3 ../tests/kms_setmode.c:883 main() > #4 ../csu/libc-start.c:342 __libc_start_main() > #5 [_start+0x2e] > Subtest basic failed. > **** DEBUG **** > > So after in digging into the below comments it turns out that > *confidence interval* with respect to standard deviation is calculated > with *Cumulative distribution function* (formula) > > As per the Wikipedia table > For various values of z, the percentage of values expected to lie in and outside the symmetric interval, CI = (−zσ, zσ), are as follows: > [0] > https://en.wikipedia.org/wiki/Standard_deviation#Rules_for_normally_di > stributed_data > > It turns out that *3 σ* gives around proportion percentage 99.7300204% which is according to the CI = (−zσ, zσ) table. > > I would like to submit a below patch as this changes fix the overall bug. > Please share your thought and suggestion on any alternative approach I should try. You would also have to update the comments as it no longer matches the broaden 90% critical value. Still debating what is a sensible error rate, but in the meantime I would suggest a different approach: ignore the deviation if it is within a single scanline. Something like: - igt_assert_f(fabs(mean - expected) < 1.718 * stddev, - "vblank interval differs from modeline! expected %.1fus, measured %1.fus +- %.3fus, difference %.1fus (%.1f sigma)\n", + igt_assert_f(fabs(mean - expected) < max(line_time(kmode), 1.718 * stddev), + "vblank interval differs from modeline! expected + %.1fus, measured %1.fus +- %.3fus, difference %.1fus (%.1f sigma, %.1f + scanlines)\n", expected, mean, stddev, - fabs(mean - expected), fabs(mean - expected) / stddev); + fabs(mean - expected), + fabs(mean - expected) / stddev, + fabs(mean - expected) / line_time(kmode)); Thanks for this new approach, I have tested this patch on different machines with different modes as below. Mode: 1920x1080@60Hz Connectors: HDMI-A-2 Mode: 1920x1080@60Hz Connectors: DP-1 Mode: 1920x1080@60Hz Connectors: DP-2 Mode: 2560x1440@60Hz Connectors: eDP-1 Mode: 3840x2160@60Hz Connectors: DP-2 And all the testcase regarding kms_setmode seems to passing on 5.8.x and 5.10-0-rcx kernel. Thanks -Anand _______________________________________________ igt-dev mailing list igt-dev@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/igt-dev ^ permalink raw reply [flat|nested] 7+ messages in thread
* [igt-dev] [i-g-t] tests/kms_setmode: basic Improve accuracy with using of confidence interval @ 2020-11-02 9:02 Anand Moon 0 siblings, 0 replies; 7+ messages in thread From: Anand Moon @ 2020-11-02 9:02 UTC (permalink / raw) To: igt-dev, Dorota Czaplejewicz; +Cc: Anand Moon Using confidence interval formula accuracy is estimates approximately at 95% when {X} is the average of a sample of size n. Use this confidence interval formula as used in statistics to estimate the accuracy. Cc: Dorota Czaplejewicz <dorota.czaplejewicz@collabora.co.uk> Signed-off-by: Anand Moon <anandx.ram.moon@intel.com> --- See below link. https://en.wikipedia.org/wiki/68%E2%80%9395%E2%80%9399.7_rule#Cumulative_distribution_function --- tests/kms_setmode.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/tests/kms_setmode.c b/tests/kms_setmode.c index 92f3ead2..58814a13 100644 --- a/tests/kms_setmode.c +++ b/tests/kms_setmode.c @@ -494,7 +494,7 @@ static void check_timings(int crtc_idx, const drmModeModeInfo *kmode) * which depend on timing, giving the lowest acceptable MTBF of 5.6s * for 60Hz sampling rate. */ - accuracy = 3. * stddev; + accuracy = 3. * stddev / sqrt(CALIBRATE_TS_STEPS); igt_info("Expected frametime: %.0fus; measured %.1fus +- %.3fus accuracy %.2f%% [%.2f scanlines]\n", expected, mean, stddev, -- 2.25.1 _______________________________________________ igt-dev mailing list igt-dev@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/igt-dev ^ permalink raw reply related [flat|nested] 7+ messages in thread
end of thread, other threads:[~2020-11-23 13:57 UTC | newest] Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2020-11-02 9:08 [igt-dev] [i-g-t] tests/kms_setmode: basic Improve accuracy with using of confidence interval Anand Moon 2020-11-03 10:49 ` Chris Wilson 2020-11-03 17:58 ` Ram Moon, AnandX 2020-11-20 9:12 ` Ram Moon, AnandX 2020-11-20 15:05 ` Chris Wilson 2020-11-23 13:57 ` Ram Moon, AnandX -- strict thread matches above, loose matches on Subject: below -- 2020-11-02 9:02 Anand Moon
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