For example, the code: integer i,j,k i = 1 j = 0 k = i/j will generate the error "Arithmetic Exception: Integer divide by 0" because an attempt to divide by Following the IEEE standard, two things happen when an untrapped exception occurs during a floating-point operation: The system returns a default result. Many, if not most, floating point operations incur loss of precision due to rounding, and hence the ffpe-trap=inexact is likely to be uninteresting in practice. The first three exceptions (‘invalid’, ‘zero’, and ‘overflow’) often indicate serious errors, and unless the program has provisions for dealing with these exceptions, enabling traps for these three exceptions is probably

C C Individual call to ieee_handler accumulate the requests. list is a (possibly empty) comma-separated list of the following exceptions: ‘invalid’ (invalid floating point operation, such as SQRT(-1.0)), ‘zero’ (division by zero), ‘overflow’ (overflow in a floating point operation), ‘underflow’ sigfpe via f90 structures as per documentation in f90sigfpe.h fsigfpe(2) % abort =2 fsigfpe(2) % trace =2 ! The -fpe or /fpe option enables exceptions in the Fortran main program only.

See the Fortran User's Guide. Do you have any ideas? –MelihAltunan Apr 8 '13 at 16:04 | show 3 more comments 1 Answer 1 active oldest votes up vote 0 down vote How are you running This option only has influence for compilation of the Fortran main program. See Options for Debugging Your Program or GCC, for more information on debugging options. 4-9 MINIMIZING FLOATING-POINT ERRORS Manual safeguarding ------------------- You can check manually every dangerous arithmetic operation, special routines may be constructed to perform arithmetical operations in a safer way, or get an error message if this

Here are the NaN-trapping functions for the various compilers that are supported by GEOS-Chem: Compiler Function Result Intel Fortran Compiler (IFORT) ISNAN( x ) Returns T if x=NaN; F otherwise Sun Truth in numbers Are there any rules or guidelines about designing a flag? This is because 1+E1000 is greater than the value that can be represented by a real variable. Testing for values close to a non-zero number The procedure for testing if values lie within a specfied tolerance of a non-zero number is similar to the above example, just that

When -ftz is used without such an option, the compiler will insert code to conditionally set FTZ/DAZ based on a runtime processor check (this processor check fails for non-Intel machines). actions you take ... The standard simplifies the task of writing numerically sophisticated, portable programs. Note On systems based on the IA-32 and Intel® 64 architectures , explicitly setting -fpe1 or /fpe:1 can degrade performance since the generated code stream must be synchronized after each floating-point

Bibliography ------------ An excellent article on floating-point arithmetic: David Goldberg What Every Computer Scientist Should Know about Floating-Point arithmetic ACM Computing Surveys Vol. 23 #1 March 1991, pp. 5-48 An old Choice of algorithms is another critical issue. It may depend on the particular implementation. Since an infinite value cannot be represented by the computer, an error occurs.

Not the answer you're looking for? A . Trap REAL*4 infinity values IF ( VALUE == Z'7F800000' .or. & VALUE == Z'FF800000' ) THEN IT_IS_A_FINITE = .FALSE. The Fortran names for these functions are listed in these man pages: libm_double(3f) libm_single(3f) ieee_functions(3m) Also see: ieee_values(3m) The floatingpoint.h header file and floatingpoint(3f) 6.3.3 Exception Handlers and ieee_handler() Typical concerns

else samesign = .true. When compiling different routines in a program separately, you should use the same value of n in -fpen. TRAP_FPE is an excellent trapping interface. However, it is often better to test whether the variable is within some tolerance of a given value.

REAL*16 takes more CPU time than REAL*8/REAL*4, but introduces very small roundoff errors, and has a huge range. Intel® EM64T-based systems have both FTZ and DAZ hardware flags. Another possible cause is an argument list in a call statement that does not contain the same variable types as the subroutine declaration. For example, if you declared an array as: real foo(10,5) and attempted to access element foo(32,3), a segmentation violation would occur because the value 32 is greater than the dimension of

For the system to generate a SIGFPE, exception trapping must first be enabled, usually by a call to ieee_handler(). 6.3.3.1 Establishing an Exception Handler Function To establish a function as an The three most common errors are segmentation violations, bus errors, and arithmetic exceptions. Using the appropriate computer arithmetic is another. An interval is the closed compact set: [a, b] ={z | a z b} defined by a pair of numbers, a b.

To get more detailed location information about where the exception occurred, use -traceback (Linux and Mac OS) or /traceback (Windows). To get more detailed location information about where the exception occurred, use -traceback. Operation produces a result that exceeds the range of the exponent-- for example, MAXDOUBLE+0.0000000000001e308 Underflow. Target value IF ( ABS( X - VALUE ) < EPSILON ) THEN PRINT*, 'X is within +/- EPSILON of 20.' ELSE PRINT*, 'X is not within +/- EPSILON of 20.'

IEEE underflow condition (Underflow Raised) res_uflow = small * scale write(6,100)"Underflow: ",small, " *", scale, " = ", res_uflow ! this is not easy to achieve as the following example will show. Does anyone have a suggestion? Example: A convergence test based on the smallest number supported by the hardware would look like: IF ( delta .LE.

To find out what a vendor offers for FPE trapping and handling, you can browse the vendor's online documentation, using the search engine and search words like "FPE" and "signal." Looking The advantage of compiling with -ftrap=common is that the source code need not be modified to trap the exceptions. stop the code here ... But underflow is not a problem since Cray arithmetic automatically cuts over to zero.

Floating-point overflow, floating-point divide-by-zero, and floating-point invalid produce exceptional values (NaN and signed Infinities) and execution continues.