11 August 2011

ça marche (mal?)

Suzerain, my pseudospectral, compressible DNS code, is coming along.  After some manufactured solution love I'm onto channel problems.  With some added solenoidal velocity perturbations my laminar solutions transitioned to turbulent ones quite nicely.

However, I'm currently puzzling over why my Coleman-like case is showing stationary mean state behavior...

 ...but momentum fluctuations that grow in time:

Currently suspect things are:
  1. Inadequate resolution ('tis quite lousy)
  2. Pressure growing in time (a probable symptom I need to check but not a root cause)
  3. Funkiness associated with the discrete mass conservation fixes (my numerics are not conservative and holding mass constant requires some integral constraint futzing)
  4. Inadequate dealiasing (unlikely, currently using enough to handle quadratic nonlinearities in my Fourier directions but my equations are worse-than-cubic).
 Thank you to Nick Malaya for poring over plots with me this morning.

09 August 2011

Welcome to a dumber planet.

Consider IBM's stock price over the last several years...

...and then today's news that IBM Terminated The Blue Waters Contract because of financial, rather than technical, reasons:
When HPCwire spoke with Herb Schultz, marketing manager for IBM's Deep Computing unit, last year, he outlined a new business model that would apply a lot more scrutiny to how the company positioned its high-end supercomputers. "There is really no appetite in IBM anymore -- with some of the leadership changes over the last few years -- for revenue that has no profit with it," he told us back in November 2010....  From NCSA's perspective, the system met all of its technical requirements. In particular, they appeared confident the machine, based on Power 755 servers, would indeed be able to deliver a sustained petaflop from its 10-petaflop peak performance.... The most curious aspect of the IBM pull-out is that they had already delivered three racks of Power 755 servers to NCSA.
It is a sad day when a screamingly profitable U.S. company reneges on a contract so fundamental to the next decade of basic U.S. science.  Especially a contract where even the worst imaginable outcome for IBM has no potential to noticeably impact shareholder returns for even a single quarter.

Subscribe Subscribe to The Return of Agent Zlerich