Mailing List Archive

[PATCH] tests: Fix test-checksum to move the mod operation up
From: Athira Rajeev <atrajeev@linux.vnet.ibm.com <mailto:atrajeev@linux.vnet.ibm.com>>

testchecksum fails with "verify: isisd failed" for few iterations.
Checking the test code, it calls iso_csum_create followed by verify function
where it fails in some cases.

Code snippet:

isisd = iso_csum_create (buffer, exercise + sizeof(u_int16_t), exercise);
if (verify (buffer, exercise + sizeof(u_int16_t)))
printf ("verify: isisd failed\n");

In iso_csum_create , code uses modulo ( % ) operation.
Code snippet:
========
mul = (init_len - off) * c0;

x = mul - c1 - c0;
y = c1 - mul - 1;

if (y > 0)
y++;
if (x < 0)
x--;

x %= 255;
y %= 255;

if (x == 0)
x = 255;
if (y == 0)
y = 1;
========

Moved the modulus operation up the if condition in testcase and
isisd verify goes fine without reporting fail.
Referring this mail thread https://lists.gt.net/quagga/dev/17347 <https://lists.gt.net/quagga/dev/17347>
and https://github.com/Quagga/quagga/commit/5d4b8cf2faba9f5386810a7c70837e5b7fae3572#diff-5fb4cfc11e8bb396af1ce29581abfb89 <https://github.com/Quagga/quagga/commit/5d4b8cf2faba9f5386810a7c70837e5b7fae3572#diff-5fb4cfc11e8bb396af1ce29581abfb89> ,
mod operation was moved up for "reduce_isisd_mod" in past commits.

Also observed that without moving mod up and introducing sleep after mod operation also solves the issue :

--- test-checksum.c.org <http://test-checksum.c.org/> 2017-08-23 12:19:43.688263168 +0000
+++ test-checksum.c 2017-08-23 12:22:43.400260726 +0000
@@ -360,6 +360,8 @@ iso_csum_create (u_char * buffer, testsz
x %= 255;
y %= 255;

+ sleep(1);
+
if (x == 0)
x = 255;
if (y == 0)

Reason behind this appears that modulus operator is slow.
Reference links:
https://stackoverflow.com/questions/27977834/why-is-modulus-operator-slow <https://stackoverflow.com/questions/27977834/why-is-modulus-operator-slow>

But Since "Moving the mod up" was followed as solution in past commits, adding that patch here.

Signed-off-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com <mailto:atrajeev@linux.vnet.ibm.com>>
---
tests/test-checksum.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/tests/test-checksum.c b/tests/test-checksum.c
index b6741f30..99d255ef 100644
--- a/tests/test-checksum.c
+++ b/tests/test-checksum.c
@@ -352,14 +352,14 @@ iso_csum_create (u_char * buffer, testsz_t len, testoff_t off)
x = mul - c1 - c0;
y = c1 - mul - 1;

+ x %= 255;
+ y %= 255;
+
if (y > 0)
y++;
if (x < 0)
x--;

- x %= 255;
- y %= 255;
-
if (x == 0)
x = 255;
if (y == 0)
--
2.11.0 (Apple Git-81)
Re: [PATCH] tests: Fix test-checksum to move the mod operation up [ In reply to ]
Hi All,
Please help me with review

Thanks
Athira Rajeev

> On 24-Aug-2017, at 12:45 PM, Athira Rajeev <atrajeev@linux.vnet.ibm.com> wrote:
>
> From: Athira Rajeev <atrajeev@linux.vnet.ibm.com <mailto:atrajeev@linux.vnet.ibm.com>>
>
> testchecksum fails with "verify: isisd failed" for few iterations.
> Checking the test code, it calls iso_csum_create followed by verify function
> where it fails in some cases.
>
> Code snippet:
>
> isisd = iso_csum_create (buffer, exercise + sizeof(u_int16_t), exercise);
> if (verify (buffer, exercise + sizeof(u_int16_t)))
> printf ("verify: isisd failed\n");
>
> In iso_csum_create , code uses modulo ( % ) operation.
> Code snippet:
> ========
> mul = (init_len - off) * c0;
>
> x = mul - c1 - c0;
> y = c1 - mul - 1;
>
> if (y > 0)
> y++;
> if (x < 0)
> x--;
>
> x %= 255;
> y %= 255;
>
> if (x == 0)
> x = 255;
> if (y == 0)
> y = 1;
> ========
>
> Moved the modulus operation up the if condition in testcase and
> isisd verify goes fine without reporting fail.
> Referring this mail thread https://lists.gt.net/quagga/dev/17347 <https://lists.gt.net/quagga/dev/17347>
> and https://github.com/Quagga/quagga/commit/5d4b8cf2faba9f5386810a7c70837e5b7fae3572#diff-5fb4cfc11e8bb396af1ce29581abfb89 <https://github.com/Quagga/quagga/commit/5d4b8cf2faba9f5386810a7c70837e5b7fae3572#diff-5fb4cfc11e8bb396af1ce29581abfb89> ,
> mod operation was moved up for "reduce_isisd_mod" in past commits.
>
> Also observed that without moving mod up and introducing sleep after mod operation also solves the issue :
>
> --- test-checksum.c.org <http://test-checksum.c.org/> 2017-08-23 12:19:43.688263168 +0000
> +++ test-checksum.c 2017-08-23 12:22:43.400260726 +0000
> @@ -360,6 +360,8 @@ iso_csum_create (u_char * buffer, testsz
> x %= 255;
> y %= 255;
>
> + sleep(1);
> +
> if (x == 0)
> x = 255;
> if (y == 0)
>
> Reason behind this appears that modulus operator is slow.
> Reference links:
> https://stackoverflow.com/questions/27977834/why-is-modulus-operator-slow <https://stackoverflow.com/questions/27977834/why-is-modulus-operator-slow>
>
> But Since "Moving the mod up" was followed as solution in past commits, adding that patch here.
>
> Signed-off-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com <mailto:atrajeev@linux.vnet.ibm.com>>
> ---
> tests/test-checksum.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/tests/test-checksum.c b/tests/test-checksum.c
> index b6741f30..99d255ef 100644
> --- a/tests/test-checksum.c
> +++ b/tests/test-checksum.c
> @@ -352,14 +352,14 @@ iso_csum_create (u_char * buffer, testsz_t len, testoff_t off)
> x = mul - c1 - c0;
> y = c1 - mul - 1;
>
> + x %= 255;
> + y %= 255;
> +
> if (y > 0)
> y++;
> if (x < 0)
> x--;
>
> - x %= 255;
> - y %= 255;
> -
> if (x == 0)
> x = 255;
> if (y == 0)
> --
> 2.11.0 (Apple Git-81)
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