# PetscIsInfReal
Returns whether the input is an infinity value. 
## Synopsis
```
#if defined(PETSC_USE_REAL___FLOAT128)
PetscBool PetscIsInfReal(PetscReal a)
```

## Input Parameter

- ***a -*** the floating point number



## Developer Notes
Uses the C99 standard `isinf()` on systems where it exists.

Otherwise uses (a && a/2 == a), note that some optimizing compilers compile out this form, thus removing the check.




## See Also
 `PetscIsNormalReal()`, `PetscIsNanReal()`

## Level
beginner

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/sys/utils/mathinf.c.html#PetscIsInfReal">src/sys/utils/mathinf.c</A>


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