Search found 17 matches

by wmartin
Wed Dec 06, 2017 6:36 pm
Forum: ROMS Benchmarks
Topic: Benchmarking Epyc, Ryzen, and Xeon: Tyranny of Memory
Replies: 5
Views: 3622

Re: Benchmarking Epyc, Ryzen, and Xeon: Tyranny of Memory

Jamie, thank you for your quick reply. Reading your note was a little confusing. I wondered if you have heard of the TR 1900x with 8 cores for about $500? It has four channels and runs a bit faster than the 1920x (same overclock numbers) but has less cache: L1/L2/L3 = 768K/4MB/16MB vs 1.125/6/32. I ...
by wmartin
Sun Dec 03, 2017 10:09 pm
Forum: ROMS Benchmarks
Topic: Benchmarking Epyc, Ryzen, and Xeon: Tyranny of Memory
Replies: 5
Views: 3622

Re: Benchmarking Epyc, Ryzen, and Xeon: Tyranny of Memory

Jamie This is great and very reasonable info. Thanks. I want to build a ROMS system for under or around $2k and was headed toward THreadRipper. Using PartsPicker I have been able to put together: Thread Ripper 1900, MSI 399 Motherboard, Corsair water cooling, DDR4 4x4k 3200 memory, Samsung 1Tb SSD, ...
by wmartin
Wed Jan 30, 2008 4:34 pm
Forum: ROMS Problems
Topic: small diagnostic bias
Replies: 0
Views: 857

small diagnostic bias

I am looking at residual diagnostic terms in a tidal application. I use a very strong low pass filter and the results, especially for u_accel are small compared to the tidal values. I get a very small negative bias on the u_accel term which becomes important in the residual. The bias is present in t...
by wmartin
Sun Sep 02, 2007 7:53 pm
Forum: ROMS Discussion
Topic: eddy viscosity in stratified regions due to internal waves
Replies: 2
Views: 1475

Thank you for the references. However, they discuss the removal of tke due to the generation of new internal waves from turbulence (a process which has generated a major debate between those two groups). I am more concerned with additions to the effective eddy viscosity by unresolved internal wave p...
by wmartin
Fri Aug 31, 2007 6:36 pm
Forum: ROMS Discussion
Topic: eddy viscosity in stratified regions due to internal waves
Replies: 2
Views: 1475

eddy viscosity in stratified regions due to internal waves

I am modeling a large tidal strait (Juan de Fuca) where the internal wave field is strong. I have been looking for a way to incorporate the impact of IW's in the eddy viscosity. Sukoriansky, et al. (NPG V13 pg 9) have recently proposed a scheme called Quasi-normal scale elimination (QNSE) which prop...
by wmartin
Fri Aug 25, 2006 9:07 pm
Forum: ROMS Problems
Topic: stations output for u and v seems to be shifted
Replies: 2
Views: 1497

stations output for u and v seems to be shifted

I seems to me that the interpolation code for stations is shifting u and v by one node. For example, if you have a uniform x grid at 1km spacing, the value of u at the 8km station seems to be the average of values at 6.5 km and 7.5 km in the u grid (rather than 7.5 and 8.5). I see a similar thing fo...
by wmartin
Tue Feb 21, 2006 2:07 am
Forum: ROMS Problems
Topic: tracer diagnostics
Replies: 5
Views: 3478

tracer diagnostics fix for MPDATA

The code posted by CAE above matches what I came up with and it works for me as well. There are a couple of places in the .F file where it also needs #ifdef DIAGNOSTIS_TS so it won't get included if the diagnostics are not on. In working on this problem I also found that the diagnostics don't reset ...
by wmartin
Sat Feb 04, 2006 3:38 am
Forum: ROMS Problems
Topic: tracer diagnostics
Replies: 5
Views: 3478

TS diagnostics with MPDATA

I have been having similar problems with the T and S diagnostics. After looking at the code in step3d_t_tile, I think there may be a problem when the MPDATA option is set. In that case it looks like the basic horizontal and vertical advection terms are computed and summed without any calculation of ...
by wmartin
Mon Jan 23, 2006 5:01 pm
Forum: ROMS Problems
Topic: slow salinity instability at base of steep bathymetry
Replies: 1
Views: 1879

salt buildup

Hi Amanda
I had somthing similar where things built up beyond any value that was set at the boundary. I don't remember what it was, but I think I found it by looking at the detailed diagnostic output for tracers and seeing what the source was.

Wayne
by wmartin
Mon Aug 22, 2005 8:02 pm
Forum: ROMS Discussion
Topic: Stretching parameters - vertical coordinates
Replies: 6
Views: 5526

Getting resolution a the bottom

I have the same situation, i.e. no surface forcing but a lot going on at the bottom. I have used a simple parabolic form: Cs = (1-s)^2 -1, without any problems. You can tweak the exponent to change the mix. However, I switched back to the standard formula just to stay in sync with other people worki...
by wmartin
Mon Aug 15, 2005 6:18 pm
Forum: ROMS Documentation
Topic: Suggestions
Replies: 13
Views: 11860

Notes on the examples.

All the examples that come witH ROMS could be significantly more useful if the people who set them up would write a short note on why they chose the options that they did. For example, why choose one advection scheme over another for an estuary, or why use certain values of AkV_BAC. Why use SPLINES....
by wmartin
Wed Jul 20, 2005 10:48 pm
Forum: ROMS Problems
Topic: reconciling w and dzeta/dt
Replies: 1
Views: 1784

I'll answer my own question, which mightl help someone else someday. I should have followed the basic rule: " when things look funny, increase the sampling rate." The wave motions which I thought I was seeing (and seemed to match what I expected) where aliased snapshots of an unexpected, much higher...
by wmartin
Mon Jul 18, 2005 10:59 pm
Forum: ROMS Problems
Topic: reconciling w and dzeta/dt
Replies: 1
Views: 1784

reconciling w and dzeta/dt

I've got a bunch of simulations, some of which get pretty violent, where w and zeta don't seem to match. In a rectangular channel model I get a big standing wave across the channel which looks realistic except the surface is going up when w in the top layer is negative. Sometimes it seems to be exac...
by wmartin
Wed May 25, 2005 4:26 am
Forum: ROMS Usage
Topic: Open Boudary Conditions: Inflow
Replies: 11
Views: 7756

I have a question along these lines. Basically, What is the relationship/ interdependence between tidal forcing and the climatology codes. I have been doing a bunch of simple runs in a non-rotating, unstratified, rectagular channel just to understand how the tidal forcing and OBC's work. I am using ...
by wmartin
Tue Mar 29, 2005 10:45 pm
Forum: ROMS FAQ
Topic: Tidal forcing at the open boundary
Replies: 23
Views: 42382

testing different obc's for tidal applications

I am modeling tidal flows over rough topography, in particular the Strait of Juan de Fuca. I have been reading up on obc's and have found the literature dealing with conditions along a coast and without tides (Chapman, Marchesiello, Palma). Does anyone know of any quantitative evaluation of OBC's in...
by wmartin
Tue Mar 29, 2005 10:28 pm
Forum: ROMS Bugs
Topic: Tidal constituents bug
Replies: 4
Views: 3134

multiple tidal constituents are not scaled properly

I've been working on what I think is a related problem I found that with more than one tidal component only the first one gets scaled, so for example, the angle of the ellipse, UV_Tangle, for the second component gets used in ROMS as degrees instead of radians. This is because the variable Npts in n...
by wmartin
Mon Sep 27, 2004 8:00 pm
Forum: ROMS FAQ
Topic: Using stations in ROMS
Replies: 4
Views: 5941

Using stations in ROMS

I've just started using ROMS and wanted to use the stations output options. I don't see any references to this feature anywhere in the forum. Is it used much? Has anybody got a sample input file?

Thanks