i use visual studio 2019 and intel fortran compiler 2021. in Fortran programming language for example when a number divided by zero, i want to stop program and show an error.
how to do this?
If you look at the floating point properties for your project you will find the mathematical error handing options available.
Select /fpe:0 to produce exceptions instead of NaN
Related
I am new to Fortran and coding in general so I apologize if my terminology is not correct.
I am using a Linux machine with the gfortran compiler.
I am doing research this summer which involves me getting a program written in about 1980 working again. It is written in Fortran 77. I have all the code as well as some documentation about it.
In its current form it I am receiving a "IEEE_UNDERFLOW_FLAG IEEE_DENORMAL" error. My first thought is that this code was meant to be developed under a different environment/architecture.
The documentation states “This program was designed to run on the HARRIS computer system. It also can be run on VAX system if the single precision variables are changed into double precision variables both in the main code and the subroutine package.”
I have tried changing the single precision variables to double precision variables, but I may have done that wrong. If this is the correct thing to do any insight would be great.
I have also tried compiling the coding with -std=legacy and -m32. I receive the same error from this as well.
Any advice to get me going in the right direction would be greatly appreciated.
"IEEE_UNDERFLOW_FLAG IEEE_DENORMAL is signalling" is not that uncommon. It is NOT an error message.
The meaning is that there are denormal numbers generated when running the code.
It may be a hint about numerical problems in your code, but it is not an error per se. Probably it means that your program finished successfully.
Fortran in its latest edition requires that all floating point exceptions that are signalling be reported when a STOP statement is executed. See gfortran IEEE exception inexact BTW, that also means that your program is not being compiled as Fortran 77 but as Fortran 2003 or higher.
Note that even if you request the Fortran 95 standard by -std=f95 the note is still displayed, but it can be controlled by the -ffpe-summary=list flag.
The linked answer also says that a way to avoid these warnings is to not finish the program by a STOP statement, but by running till the END PROGRAM. If you have something like
STOP
END
or
STOP
END PROGRAM
in your code, just remove the STOP, it is useless, if not even harmful.
You may but you don't have to be successful in getting rid of that by using double precision. If there are numerical problems in the algorithms, they will stay there even with doubles. But they may become less apparent. Or they might not, it depends. You don't have to re-write your code for that, just use -fdefault-real-8 or -freal-4-real-8 or similar. Read more about these options in your gfortran manual. You could even try quadruple precision, but double should normally be sufficient for all reasonable algorithms.
I converted some matlab code to c++. Some lines of the code have about 250,000 length. In addition, they involve very big mantissa numbers such as “2.209647215146515615616515615615103202897891
316e-258” and the precision is important to me (I know the number is very near to zero, but I can’t replace it with zero).
These codes run in matlab perfectly (fast and exact), but in c++, there is some problem:
First: the build time takes too long.
Second: after spend a long time for build, it works very very very slow!
I’m Using Visual Studio 2015 and when write this codes in it, it stopped working because of the huge size of lines and preprocessing tasks and I have to restart it.
Is there any way to work with long lines of code and very big numbers in c++ and Visual Studio IDE?
You might want to try GMP from gmplib.org
GMP is a free library for arbitrary precision arithmetic, operating on
signed integers, rational numbers, and floating-point numbers. There
is no practical limit to the precision except the ones implied by the
available memory in the machine GMP runs on. GMP has a rich set of
functions, and the functions have a regular interface.
You're question is very broad though plus since you're using Visual Studio it might be a nightmare to compile this with your existing library. I suggest you go over to Linux and work on that for "scientific computation".
I am trying to use the FFTW library in a Visual Studio project, and I am having trouble with getting the floating point precision to work. I have created the library files and linked them as in this post and I have only included the libfftw3f-3.lib library as it says in their documentation, and everything else is fine except for the fftw_plan_dft_r2c_2d() function. It will not accept my array of type float* for parameter 3 because it is incompatible with its argument of type double*. I understand it is just precision but, I would prefer to use floating point because fftw does support it, and b/c of the way I am memcpy() 'ing data from a float array. I am just having issues with fftw library using floating point. I havent seen anything specific on this in their Windows section like in their Unix section besides linking to the libfftw3f-3.lib library. Can anyone give me clues on how to make this happen?
For single precision routines in FFTW you need to use routines with an fftwf_ prefix rather than fftw_, so your call to fftw_plan_dft_r2c_2d() should actually be fftwf_plan_dft_r2c_2d().
I'm working on updating a serialization library to add support for serializing floating point in a portable manner. Ideally I'd like to be able to test the code in an environment where IEEE754 isn't supported. Would it be sufficient to test using a soft-float library? Or any other suggestions about how I can properly test the code?
Free toolchains that you can find for ARM (embedded Linux) development, mostly do not support hard-float operations but soft-float only. You could try with one of these (i.e. CodeSourcery) but you would need some kind of a platform to run the compiled code (real HW or QEMU).
Or if you would want to do the same but on x86 machine, take a look at: Using software floating point on x86 linux
Should your library work on a system where both hardware floating point and soft-float are not available ? If so, if you test using a compiler with soft-float, your code may not compile/work on such a system.
Personally, I would test the library on a ARM9 system with a gcc compiler without soft-float.
Not an answer to your actual question, but describing what you must do to solve the problem.
If you want to support "different" floating point formats, your code would have to understand the internal format of floats [unless you only support "same architecture both ends"], pick the floating point number apart into your own format [which of course may be IEEE-754, but beware of denormals, 128-bit long doubles, NaN, INFINITY, and other "exception values", and of course out of range numbers], and then put it back together to the format required by the other end. If you are not doing this, there is no point in hunting down a non-IEEE-754 system, because it won't work.
I've configured Visual Studio to throw floating point exceptions via the _controlfp function. This works for NAN and INF, but not QNAN. I.e. Quiet NaNs don't cause an exception to be raised. Is there any function, or config option for Visual Studio 2008/2010, that will force QNANs to instead be NANs, so that they throw exceptions?
Some helpful tips, although I've never even remotely done something like this:
Read: http://www.cisl.ucar.edu/docs/trap.error/errortypes.html
The resulting search on the internet (which I've really only spent about 30 seconds on), leads me to believe that this is normally enabled with a compiler option.
However, I also seem to recall that such enabling/disabling of traps can be specified programmatically, and especially in windows, this can be done by pretty much any program, such as when a printer is used for printing. Additionally, if you change this option programmatically, please set it back to the previous value as soon as you can, otherwise if people from .NET try to use your code, they might have issues.
(In other words, your use of _controlfp could be overriden by some other routine, assuming that is indeed the correct approach to use)
Also see Visual Studio C++ 2008 / 2010 - break on float NaN