Arithmetic Error Floating Underflow Idl

Toolkit APIs ENVI API ESE API Libraries Astronomy Library Beaumont Library Bowman Library Catalyst Library Coyote Library Dáithí Library Galloy Library program caused arithmetic error floating underflow JBIU Library JHUAPLS1R Library Mankoff Library Markwardt Library Motley Library

Gradual Underflow

Salvaggio Library ENVI Using ENVI Modules Atmospheric Correction DEM Extraction ENVI Photogrammetry Feature Extraction (FX) NITF idl floating illegal operand ENVI API ESE Using ENVI Services Engine ENVI Services Engine API ENVI for ArcGIS@ Services Edition Resources Licensing PDF Guides Platform Support Harris Geospatial/Docs Center/IDL Reference/Math -

Idl !except

Error Assessment/CHECK_MATH CHECK_MATH CHECK_MATH The CHECK_MATH function returns and clears the accumulated math error status. Examples To simply check and clear the accumulated math error status using all the defaults, enter: PRINT, CHECK_MATH() IDL prints the accumulated math error status code and resets to zero. For more examples, please see Additional Examples near the bottom idl find nan of this topic. Syntax Result = CHECK_MATH( [,MASK=bitmask] [,/NOCLEAR] [,/PRINT] ) Return Value The returned value is the sum of the bit values (described in the following table) of the accumulated errors. Value Condition 0 No errors detected since the last interactive prompt or call to CHECK_MATH 1 Integer divided by zero 2 Integer overflow 16 Floating-point divided by zero 32 Floating-point underflow 64 Floating-point overflow 128 Floating-point operand error. An illegal operand was encountered, such as a negative operand to the SQRT or ALOG functions, or an attempt to convert to integer a number whose absolute value is greater than 231 - 1 Note: CHECK_MATH can only relay information reported by the underlying hardware. Some hardware/operating system combinations may not report all of the math errors listed. Each type of error is only represented once in the return value—any number of “Integer divided by zero” errors will result in a return value of 1. The math error status is cleared (r

nonsense, can I turn the darn things off? ANSWER: Our answer today is provided by the ever-reliable math guy, Craig Markwardt, along with George N. White III and Paul van Delst. First, Craig. In all likelihood you

Floating Overflow

can ignore the overflow and underflow messages. You can use !EXCEPT=2 to find out where

Overflow And Underflow In Data Structures

in your program the exceptions are being created. You can also turn off exceptions using !EXCEPT=0, if that is crucial. While I overflow and underflow in computer architecture have argued in the past that most people don't need underflow errors, and that they should be silent, other folks on the newsgroup have argued that we should strive to avoid them, so such errors should be http://www.harrisgeospatial.com/docs/CHECK_MATH.html printed. Leaving the question of right verses wrong on error messages aside for the moment, I indeed think it is important to avoid over and underflows. My guess is that you are getting both when you use EXP() in the Fermi distribution. To avoid this you can use some simple techniques. One idea is to use thresholding to keep all values in-bounds, like this, EXP((X) > (-1e-38) < 1e38). That is not really satisfactory http://www.idlcoyote.com/math_tips/underflow.html though, because sometimes you *want* the effect of an underflow. That is perhaps best solved using the WHERE() command to locate extremal values and treat them specially. Paul mostly concurs. First test your code after setting !EXCEPT=2. This will tell you on what lines of code you are getting the overflow/underflow. Then you can alter your algorithm to avoid them depending on your needs. For example, if the numerical precision is a good enough tolerance level, you can do something like this. ; Set some tolerance level, with double keyword just in case. tolerance = ( machar(double=double) ).eps if ( x LT tolerance ) then $ result = KEYWORD_SET( double ) ? 0.0d0 : 0.0 $ else $ result = y / x I think a lot of people will think this is probably overkill, and maybe it is for what you want to do. My recent experience has shown, in general, that you can ignore the underflow errors if (1) you are sure your code will always be executed in the same regime, and (2) you don't care if you code crashes and burns, or produces a crappy number every now and again. I say this because the global forecast model I use here runs up to about the 2hPa pressure level. At these high altitudes the amount of w

Projections Active Contouring Coyote Programs For Sale Other Programs Books Coyote's Guide to Traditional IDL Graphics IDL Programming Techniques, 2nd Ed. Plot Gallery Store Courses IDL Links Reviews 2007 Book Reviews 2008 Book Reviews 2009 Book Reviews 2010 Book Reviews 2011 Book Reviews Contact http://www.idlcoyote.com/code_tips/maxminnans.php Making IDL Operators Play Nice with NaNs QUESTION: The minimum and maximum operators do not work nicely with NaN values. Consider this code. IDL> a = Findgen(5) IDL> a[2] = !Values.F_NaN IDL> Print, a 0.00000 1.00000 NaN 3.00000 http://stackoverflow.com/questions/18716543/arithmetic-error-floating-illegal-operand-idl 4.00000 IDL> b = a > 2 % Program caused arithmetic error: Floating illegal operand IDL> Print, b 2.00000 2.00000 2.00000 3.00000 4.00000 I think most people would say that the proper behavior would be for the NaN value arithmetic error to be preserved. The IDL documentation indicates the behavior is actually hardware dependent, and on some machines the NaN is preserved. It suggests using Where and Finite instead of ">", whenever NaN values are present. IDL> b = a IDL> goodIndices = Where(Finite(a), count) IDL> IF count GT 0 THEN b[goodIndices] = a[goodIndices] > 2 IDL> Print, b 2.00000 2.00000 NaN 3.00000 4.00000 The syntax above also eliminates the annoying "illegal operand" error message. The documentation also indicates arithmetic error floating that the ">" operator does not check for NaN values for speed reasons, and that the syntax of the operator does not allow having a NaN keyword be used with it. A related problem occurs with the Hist_Equal function. IDL> Print, Hist_Equal(a) 0 85 0 170 255 % Program caused arithmetic error: Floating illegal operand In this case, it is correct that the NaN is not preserved, since the output of Hist_Equal is a byte array. But I think it is a bug that the illegal operand error occurs. Hist_Equal does check for NaN values internally (for example, the internal Histogram command is called with the NaN keyword). It is only at the last step in Hist_Equal, where the > operator is used, that the NaN values are ignored. In this case, I think ExelisVis should follow their own advice and use Where and Finite rather than the > operator, even though doing so would make this a much slower operation. Any ideas about this? ANSWER: Well, I completely agree it is always best to follow your own advice, but you can see how far this gets you in your own life, probably. I do note there is a faster way of obtaining the same result, without resorting to the Where and Finite functions, although you still get the dreaded illegal operand error, unfortunately. This syntax is about twice as fast

here for a quick overview of the site Help Center Detailed answers to any questions you might have Meta Discuss the workings and policies of this site About Us Learn more about Stack Overflow the company Business Learn more about hiring developers or posting ads with us Stack Overflow Questions Jobs Documentation Tags Users Badges Ask Question x Dismiss Join the Stack Overflow Community Stack Overflow is a community of 4.7 million programmers, just like you, helping each other. Join them; it only takes a minute: Sign up arithmetic error: Floating illegal operand [IDL] up vote 0 down vote favorite I have this code: close, 1 & openr,1,filename,error=err if (err ne 0) then begin close, 1 n=0 return endif line=fltarr(41) while(not(eof(1))) do begin readf,1,line endwhile And on the line readf,1,line I get the following error: READF: End of file encountered. Unit: 1, File: results Program caused arithmetic error: Floating illegal operand I see what the cause is and I read the docs about it, but I still don't understand what arithmetic error has to do with EOF (why EOF? I checked if not(eof(1))) and what to do to get rid of this error. Do you have any ideas? runtime-error eof idl-programming-language share|improve this question asked Sep 10 '13 at 10:30 alex 2,748103264 add a comment| 2 Answers 2 active oldest votes up vote 1 down vote accepted The illegal floating point operation is probably not from not(eof(1)) but from readf, 1, line or carried over from another portion of the code. IDL is expecting to read in 41 32-bit float values, but some or all of the values it reads in are not valid floating point numbers. Not all 32-bit series of 1s and 0s make a valid IEEE float32 (the "float" values used in IDL and most other languages). If you inadvertently encounter the end of the file, there's a high chance that some of the data read from the file won't fit nicely into a float32. When that happens, IDL will attempt to make an informed guess as to which float number your data should have been, but doing so is not technically part of the IEEE standard, so it raises the Program caused arithmetic error: Floating illegal operand error. To investigate, you might like to try substituting the following code: close, 1 & openr, 1, filename, error=err if (err ne 0) then begin close, 1 n = 0 return endif line = bytarr(41 * 4) while not(eof(1)) do begin readf, 1, line endwhile In this case, because you are reading into a byte array instead of a float array, the only error should be READF: End of file encountered. Unit: 1, File: res