[mpich-discuss] Custom rank for processes

Mon Jul 1 15:17:00 CDT 2024

Thank you Joachim and Hui.

-rankmap {rank map} comma separated rank to node id list

How is the format if I have 4 processes ?

mpirun -prepend-rank -n 5 -hosts 192.168.2.100,192.168.2.200 hello-world

How do I add rankmap to the above? Just add ranks 0,1,2,3 after –rankmap?

Secondly, can I pin each of these 5 processes to a particular core?

Could you give an example of the “user” option?

user:0+2,1+4,3,2 -- user specified binding

does the above mean rank 0 will run on 2?

From: Zhou, Hui <zhouh at anl.gov>
Date: Monday, July 1, 2024 at 3:10 PM
To: discuss at mpich.org <discuss at mpich.org>, Jenke, Joachim <jenke at itc.rwth-aachen.de>
Cc: Niyaz Murshed <Niyaz.Murshed at arm.com>, nd <nd at arm.com>
Subject: Re: Custom rank for processes
>What Joachim points out is that you can set a rank of 2, 3, 20, 30 if your total number of processes is 4.

Of course, I meant for "can't".

Here are some additional pointers:
* The PR adding the rankmap option: https://urldefense.us/v3/__https://github.com/pmodels/mpich/pull/6213__;!!G_uCfscf7eWS!aPnbBzYUN52PM6-sRCWAUZUrcgQItHhVgf4fNwl1F_Y9U4JgKyox4xxb6Gn5UnQ3eOBbZxJLrhjxJlSBAfE$ 
* Other options for specifying rank ordering and binding:https://urldefense.us/v3/__https://github.com/pmodels/mpich/blob/main/doc/wiki/how_to/Using_the_Hydra_Process_Manager.md__;!!G_uCfscf7eWS!aPnbBzYUN52PM6-sRCWAUZUrcgQItHhVgf4fNwl1F_Y9U4JgKyox4xxb6Gn5UnQ3eOBbZxJLrhjxZg0xIV8$ 

Hui

________________________________
From: Zhou, Hui <zhouh at anl.gov>
Sent: Monday, July 1, 2024 3:04 PM
To: discuss at mpich.org <discuss at mpich.org>; Jenke, Joachim <jenke at itc.rwth-aachen.de>
Cc: Niyaz Murshed <Niyaz.Murshed at arm.com>; nd <nd at arm.com>
Subject: Re: Custom rank for processes

Hi Niyaz,

Yes, you can use the -rankmap option to specify a full rank ordering. The syntax for rankmap string is:

```
/* rankmap string format (used in PMI_process_mapping) in ABNF:
 *
 * mapping = '(' format ',' (block / block_repeats) *[',' (block / block_repeats)] ')'
 * format = 'vector'
 * block = num / '(' num ',' num ',' num ')'
 * block_repeats = '[' block *[',' block] ']x' num
 * num = 1*DIGIT
 *
 * If a block is in 3-tuple of (X,Y,Z), the meaning is:
 *     X - node id start value
 *     Y - number of nodes with size Z
 *     Z - number of processes assigned to each node
 *
 * If a block is a single number id, it denotes the node id, which is equivallen to
 * (id, 1, 1).
 *
 * A block_repeat repeats the bracketed block list by num of times.
 */
```

What Joachim points out is that you can set a rank of 2, 3, 20, 30 if your total number of processes is 4. You can only order the processes.

Hope that helps.

--
Hui
________________________________
From: Niyaz Murshed via discuss <discuss at mpich.org>
Sent: Monday, July 1, 2024 2:43 PM
To: discuss at mpich.org <discuss at mpich.org>; Jenke, Joachim <jenke at itc.rwth-aachen.de>
Cc: Niyaz Murshed <Niyaz.Murshed at arm.com>; nd <nd at arm.com>
Subject: Re: [mpich-discuss] Custom rank for processes

Am actually trying to understand how/if I can pin a rank to a process .. also pin a core to a process. From: Niyaz Murshed via discuss <discuss@ mpich. org> Date: Monday, July 1, 2024 at 2: 34 PM To: Jenke, Joachim <jenke@ itc. rwth-aachen. de>,
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Am actually trying to understand how/if I can pin a rank to a process .. also pin a core to a process.

From: Niyaz Murshed via discuss <discuss at mpich.org>
Date: Monday, July 1, 2024 at 2:34 PM
To: Jenke, Joachim <jenke at itc.rwth-aachen.de>, discuss at mpich.org <discuss at mpich.org>
Cc: Niyaz Murshed <Niyaz.Murshed at arm.com>, nd <nd at arm.com>
Subject: Re: [mpich-discuss] Custom rank for processes

What is the rankmap used for ? From: Jenke, Joachim <jenke@ itc. rwth-aachen. de> Sent: Monday, July 1, 2024 2: 21: 53 PM To: discuss@ mpich. org <discuss@ mpich. org> Cc: Niyaz Murshed <Niyaz. Murshed@ arm. com>; nd <nd@ arm. com>

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What is the rankmap used for ?

________________________________

From: Jenke, Joachim <jenke at itc.rwth-aachen.de>
Sent: Monday, July 1, 2024 2:21:53 PM
To: discuss at mpich.org <discuss at mpich.org>
Cc: Niyaz Murshed <Niyaz.Murshed at arm.com>; nd <nd at arm.com>
Subject: Re: Custom rank for processes

MPI defines rank numbers to be consecutive from 0 to size-1. Your suggested numbering will not work.

-Joachim

________________________________

From: Niyaz Murshed via discuss <discuss at mpich.org>
Sent: Monday, July 1, 2024 9:09:41 PM
To: discuss at mpich.org <discuss at mpich.org>
Cc: Niyaz Murshed <Niyaz.Murshed at arm.com>; nd <nd at arm.com>
Subject: [mpich-discuss] Custom rank for processes

Hello, Is it possible to provide custom ranks to processes ? I see a param called “-rankmap” .. Does it provide this option? Is it possible to do something like below : Node1 => 2 processes => rank 2,3 Node2 => 2 processes => rank

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Hello,

Is it possible to provide custom ranks to processes ?

I see a param called “-rankmap” .. Does it provide this option?

Is it possible to do something like below :

Node1 => 2 processes => rank 2,3

Node2 => 2 processes => rank 20,30

Thanks.
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