CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > CFX

how much memory needed?

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Display Modes
Old   August 2, 2007, 12:11
Default how much memory needed?
  #1
jan
Guest
 
Posts: n/a
is there a way to clac how much mem you need ,to do a certain calc

like 100.000 grid cells you need ..................... mem

1.000.000 you need ...........................mem
  Reply With Quote

Old   August 2, 2007, 12:41
Default Re: how much memory needed?
  #2
Bian
Guest
 
Posts: n/a
How about doing a little experiment? Doing a couple of cases to see what is the RAM/nodes ratio.
  Reply With Quote

Old   August 2, 2007, 13:13
Default Re: how much memory needed?
  #3
jan
Guest
 
Posts: n/a
well i did just sad not enough memory so .........
  Reply With Quote

Old   August 2, 2007, 13:16
Default Re: how much memory needed?
  #4
jan
Guest
 
Posts: n/a
oops seems that i get drunk

i wanted to say

well i just did that and got a message not enough memory so................
  Reply With Quote

Old   August 2, 2007, 13:41
Default Re: how much memory needed?
  #5
Robin
Guest
 
Posts: n/a
Hi Jan,

The actual memory requirements are dependant on the equations being solved, the topology of the mesh, and the number of boundary faces, so it is very difficult to estimate.

That said, the solver does estimate the amount needed and this is reported in the OUT file. Compare what it expects to need with the amount available.

Note that there are two types of memory errors you can run into:

1. The solver underestimated the amount of memory and not enough memory has been allocated.

2. The solver could not allocate the memory requested.

How you react depends on which error you run into. If it is case 1, not enough memory allocated, increase the Memory Allocation Factor, say to 1.2 (i.e. 20% more memory) under the "Solver" tab when you define the run in the Solver Manager. For case 2 you can try decreasing it to, say, 0.9. The solver will generally overestimate the memory required, so there is usually some room for reducing it. If that doesn't work, either reduce the size of your model or run it in parallel.

Regards, Robin

  Reply With Quote

Old   August 2, 2007, 13:42
Default Side question: what browser are you using?------We
  #6
Robin
Guest
 
Posts: n/a
Hi Jan,

Your posts seem to be succeptable to the same random text as some of mine. What browser are you using?

Regards, Robin
  Reply With Quote

Old   August 2, 2007, 14:32
Default Re: Side question: what browser are you using?----
  #7
jan
Guest
 
Posts: n/a
differant computers but mostly safari on power mac
  Reply With Quote

Old   August 2, 2007, 14:41
Default so how much mem is this ???????? robin?
  #8
jan
Guest
 
Posts: n/a
+--------------------------------------------------------------------+ | Memory Allocated for Run (Actual usage may be less) | +--------------------------------------------------------------------+

Data Type Kwords Words/Node Words/Elem Kbytes Bytes/Node

Real 292156.1 300.91 95.54 1141234.8 1203.62 Integer 122312.0 125.98 40.00 477781.3 503.90 Character 2807.9 2.89 0.92 2742.1 2.89 Logical 65.0 0.07 0.02 253.9 0.27 Double 908.0 0.94 0.30 7093.8 7.48

  Reply With Quote

Old   August 2, 2007, 15:05
Default Re: so how much mem is this ???????? robin?
  #9
Robin
Guest
 
Posts: n/a
Sum up the Kbytes column for each type (the REAL and INTEGER spaces take up the bulk of it). You get:

Total Kbytes = 1141234.8 + 477781.3 + 2742.1 + 253.9 + 7093.8 Total Kbytes = 1,629,105.9

Divide by 1024 to get Mbytes... 1,590.9 Mb

Regards, Robin
  Reply With Quote

Old   August 2, 2007, 15:07
Default Re: Side question: what browser are you using?----
  #10
Robin
Guest
 
Posts: n/a
That's what I suspected. I'm running Safari on Windows and on my Mac at home.
  Reply With Quote

Old   August 2, 2007, 16:08
Default Re: Side question: what browser are you using?----
  #11
Jonas Larsson
Guest
 
Posts: n/a
I think that this is a bug in early verisions of Safari 3. Safari 2 and the latest Safari should not have it I think, but I haven't tried it.
  Reply With Quote

Old   August 2, 2007, 16:18
Default Re: Side question: what browser are you using?----
  #12
Robin
Guest
 
Posts: n/a
Hi Jonas,

I updated Safari yesterday with the latest patch but it still did it. It seems to happen for sure if you resize the text box (which you cannot do in other browsers). Other than that I can't predict it.

Nice browser otherwise.

-Robin
  Reply With Quote

Old   September 2, 2007, 18:12
Default Re: so how much mem is this ???????? robin?
  #13
klaas
Guest
 
Posts: n/a
kbytes 1164520.2 +477781.8+2742.5+253.9+7093.8

and i have 2048 mem and i still get a error not enough free mem

how come and what to do????
  Reply With Quote

Old   September 4, 2007, 09:21
Default Re: so how much mem is this ???????? robin?
  #14
Robin
Guest
 
Posts: n/a
Hi Klaas,

That would be 1613 MB. This is less than the 2048 MB you have available, however it is not usually possible to allocate all of the memory, especially if you are running on Windows. The solver will attempt to grab the largest contiguous block of Virtual Memory the OS has available (meaning that the memory is not fragmented). Most operating systems have no problem returning the full 2 GB that can be allocated with a 32 bit signed integer, but because of how Windows pre-loads DLL's, it's virtual memory address space is far more fragmented. I have heard of people maxing out with as little as 800 MB of contiguous space!

The problem really only occurs on 32 bit Windows. To avoid the problem you could run Linux, or run CFX in parallel (even on a single CPU), so that each partition requires less memory. The problem also goes away on 64 bit Windows systems, which are quickly becoming the norm anyhow (although this admittedly doesn't help you much).

Regards, Robin

  Reply With Quote

Old   September 4, 2007, 14:52
Default Re: so how much mem is this ???????? robin?
  #15
klaas
Guest
 
Posts: n/a
thanks, i tried parallel but got also error . and its a laptop so it not possible to more mem so i am stuck with this problem

  Reply With Quote

Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Memory needed for solving a 3 million model eleazar CFX 5 February 26, 2011 16:35
Estimate Memory needed for LES/VOF simulation Helmi Main CFD Forum 0 December 15, 2010 06:22
CFX CPU time & real time Nick Strantzias CFX 8 July 23, 2006 17:50
"Memory too low" problem with Fluent HELP NEEDED Amr FLUENT 6 May 8, 2006 12:06
ECC Memory Needed for Clusters? Jonas Larsson Main CFD Forum 1 January 17, 2001 09:08


All times are GMT -4. The time now is 13:21.