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Puzzle with floating point underflow [message #26334]

Thu, 23 August 2001 00:30

Martin Schultz
Messages: 515
Registered: August 1997

Senior Member

Hi all,

How can a float number be something e-42 if the system says it can only
represent numbers down to 1.e-38 in a float????????

test= 8.1047657d-42
IDL> tmp=float(test)
% Program caused arithmetic error: Floating underflow
% Detected at MGS_RGRID::REGRID 203 /pf/m/m218003/home/IDL/lib/mgs_newobjects
/mgs_rgrid__define.pro
IDL> help,tmp
TMP FLOAT = 8.10511e-42

IDL> help,machar(),/stru
** Structure MACHAR, 13 tags, length=52:
IBETA LONG 2
IT LONG 24
IRND LONG 5
NGRD LONG 0
MACHEP LONG -23
NEGEP LONG -24
IEXP LONG 8
MINEXP LONG -126
MAXEXP LONG 128
EPS FLOAT 1.19209e-07
EPSNEG FLOAT 5.96046e-08
XMIN FLOAT 1.17549e-38 <<<<<<<<<<<
XMAX FLOAT 3.40282e+38

(For those, who haven't figured this out from the Machar output: I am
running IDL5.3 on a Linux system (kernel 2.2.14))

Not a real problem because underflows are considered harmless, but I
am curious about this, anyhow.

Cheers,

Martin

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[Message index]

		Puzzle with floating point underflow By: Martin Schultz on Thu, 23 August 2001 00:30
		Re: Puzzle with floating point underflow By: Paul van Delst on Fri, 24 August 2001 07:45
		Re: Puzzle with floating point underflow By: Karl Schultz on Thu, 23 August 2001 08:29
		Re: Puzzle with floating point underflow By: Craig Markwardt on Thu, 23 August 2001 08:21

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