john-dev - Adding OpenMP support to SunMD5

Follow @Openwall on Twitter for new release announcements and other news

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <857BE162-C4D1-477B-88BA-27797795E625@gmail.com>
Date: Mon, 4 May 2015 17:26:41 +0800
From: Lei Zhang <zhanglei.april@...il.com>
To: john-dev@...ts.openwall.com
Subject: Adding OpenMP support to SunMD5

Hi,

I'm trying to add OpenMP support to SunMD5. Currently I'm looking at the biggest loop in crypt_all(), which has the form:

for (round = 0; round < maxrounds; round++)
{ ... }

It seems to me this loop has loop-carried dependence, thus not feasible for direct parallelizing. I viewed the crypt() function of some other formats, whose hotspot loops mostly have this form:

for (index = 0; index < count; index++)
{ ... }

Loops like this are easy to parallelize, since each iteration is independent. There must be other formats in JtR whose hotspot loops has loop-carried dependence, like SunMD5. How did you parallelize them?

I tried parallelizing a inner loop in the hotspot loop of SunMD5, like this:

for (round = 0; round < maxrounds; round++) {
...
	#pragma omp parallel for ...
	for (idx = 0; idx < count; ++idx)
	{ ... }
...
}

But the performance is worse than single-threaded.
	Before: 628 c/s real, 628 c/s virtual
	After:    304 c/s real, 82.4 c/s virtual

The outer loop still needs efficient handling.

Lei

Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.