[sac-dev] bugs found

[Peter Goldstein]

Brian,

Nice work fixing these bugs.

FYI, the SeisMgr code is essential when using a relational database 
as is done by the GNEM program at LLNL.
While it isn't something that is currently useful to the IRIS 
community, it seems to me that it would be
good to try and maintain this capability at some level so that it can 
be utilized should it be needed.
Given the growing DMC archive and the amount of data coming available 
from USArray I would think
that this is a realistic possibility.

Using an environment variable to turn it on or off seems like a good 
way to keep it in the code without
impacting those who don't use it.

Cheers,

Peter


At 11:19 AM -0400 6/30/06, Brian Savage wrote:
>All,
>
>A few more bugs were found in sac.  They have been fixed and should be
>available in the next release.  They are not in the repository yet, but
>will be soon.
>
>All of these bug are short, quick fixes.  Please email me and I will
>send you the appropriate files.
>
>Bug List: ( explanations below )
>- Memory Leak Bug
>- Power of 2 Bug
>- read more Bug
>
>Cheers,
>Brian
>
>Memory Leak Bug:
>-------------------------
>Multiple read commands exposes a memory leak which can become very
>large, very quickly.  I found this bug by unwittingly consuming 4 GB of
>memory while processing a large dataset.
>
>Example:
>SAC> read file1
>SAC> read file2
>...
>SAC> read filen
>
>Fix:
>The allocated memory for storing the sac data was not freed when
>executing another read call, not read more.  Calls to relamb were
>included which releases memory or frees it back to the system.  this was
>done in dfm/readfl().
>
>Power of 2 Bug:
>-----------------------
>Determining the next largest power of 2 for numbers slightly larger than
>a power of 2 returns the smaller power of 2.  The bug is in ucf/next2().
>  It can cause memory error and buffer overruns, causing sac to crash or
>experience unexpected behavior.
>
>Example:
>Number of points: 8193
>Get next largest power of 2: (should be 16384)
>ucf/next2() returns 8192
>
>Fix:
>The cause of the bug was a rounding error of a real number to an
>integer.  A call to ceil() fixes the bug, plus a check to make certain
>the returned power of 2 is larger than the initial number of points.
>
>read more Bug:
>-----------------------
>While reading a large number of files into sac using the "read more",
>sac grinds to a halt.  The problem was found in the SeisMgr code as it
>was looping over the list of files during each read more command.
>
>Example:
>SAC> read more file1
>SAC> read more file2
>...
>SAC> read more filen
>
>Fix:
>No fix for this bug has been found, but turning off the SeisMgr code
>essentially fixes the problem and does not harm to the working of sac.
>My working copy has an environment variable to indicate whether or not
>to use the SeisMgr code.  I am not certain what the advantages the
>SeisMgr code provides the sac code.  If someone has a list of the
>benefits that would be great.  The recall bug, still not fixed, is due
>to the same section of code.
>
>
>_______________________________________________
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>sac-dev at iris.washington.edu
>http://www.iris.washington.edu/mailman/listinfo/sac-dev


-- 

Peter Goldstein, Ph.D.      (925) 423-1231 (office) 
  L-103, PO Box 808        (925) 422-5844 (fax)    
  Livermore, CA 94551      peterg at llnl.gov (email) 
  web page: http://www.llnl.gov/sac