[gradsusr] division with small numbers in GrADS versions 2 and 1.9b4

[Charles Seman (NOAA Federal)]

Dear GrADS Users,

Using GrADS v2.0.a7.oga.3 to do some division with small numbers, it was 
found that for var = 1e-7, var/var = 1 as expected, but with var = 1e-8, 
var/var = undef ... and maskout() also sets the result to "undef" (when 
var is positive)... shown below are some GrADS v2.0.a7.oga.3 calculations...

ga-> var = 1e-6
Define memory allocation size = 8 bytes
Name already DEFINEd:  var.   Will be deleted and replaced.
ga-> d var/var
Result value = 1
ga-> var = 1e-7
Define memory allocation size = 8 bytes
Name already DEFINEd:  var.   Will be deleted and replaced.
ga-> d var/var
Result value = 1
ga-> var = 1e-8
Define memory allocation size = 8 bytes
Name already DEFINEd:  var.   Will be deleted and replaced.
ga-> d var/var
Result value = -9.99e+08
ga-> d maskout(var,var)
Result value = 1e-08
ga-> d maskout(var/var,var)
Result value = -9.99e+08

ga-> d 1/var
Result value = -9.99e+08
ga-> d var
Result value = 1e-08

Using a GrADS 1.9b4 version, the results are as expected all the way 
down to somewhere between 1e-37 and 1e-38:

ga-> var = 1e-7
Define memory allocation size = 4 bytes
ga-> d var
Result value = 1e-07
ga-> d var/var
Result value = 1
ga-> var = 1e-8
Define memory allocation size = 4 bytes
Name already DEFINEd:  var.   Will be deleted and replaced.
ga-> d var
Result value = 1e-08
ga-> d var/var
Result value = 1
ga-> var = 1e-10
Define memory allocation size = 4 bytes
Name already DEFINEd:  var.   Will be deleted and replaced.
ga-> d var
Result value = 1e-10
ga-> d var/var
Result value = 1
ga-> var = 1e-20
Define memory allocation size = 4 bytes
Name already DEFINEd:  var.   Will be deleted and replaced.
ga-> d var
Result value = 1e-20
ga-> d var/var
Result value = 1
...
ga-> var = 1e-36
Define memory allocation size = 4 bytes
Name already DEFINEd:  var.   Will be deleted and replaced.
ga-> d var/var
Result value = 1
ga-> var = 1e-40
Define memory allocation size = 4 bytes
Name already DEFINEd:  var.   Will be deleted and replaced.
ga-> d var/var
Result value = -9.99e+33
ga-> var = 1e-38
Define memory allocation size = 4 bytes
Name already DEFINEd:  var.   Will be deleted and replaced.
ga-> d var/var
Result value = -9.99e+33
ga-> var = 1e-37
Define memory allocation size = 4 bytes
Name already DEFINEd:  var.   Will be deleted and replaced.
ga-> d var/var
Result value = 1

Has anyone else seen this difference in division results in GrADS 
versions 2 and 1.9b4?

Thanks,
Chuck
-- 

Please note that Charles.Seman at noaa.gov should be considered my NOAA
email address, not cjs at gfdl.noaa.gov.

********************************************************************
  Charles Seman                                Charles.Seman at noaa.gov
  U.S. Department of Commerce / NOAA / OAR
  Geophysical Fluid Dynamics Laboratory         voice: (609) 452-6547
  201 Forrestal Road                              fax: (609) 987-5063
  Princeton, NJ  08540-6649            http://www.gfdl.noaa.gov/~cjs/
********************************************************************

"The contents of this message are mine personally and do not reflect any
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the United States Department of Commerce, or NOAA."