:orphan:
# PetscPreLoadBegin
Begin a segment of code that may be preloaded (run twice) to get accurate timings 
## Synopsis
```
#include <petsclog.h>
void PetscPreLoadBegin(PetscBool  flag,char *name);
```
Not Collective


## Input Parameters

- ***flag -*** `PETSC_TRUE` to run twice, `PETSC_FALSE` to run once, may be overridden
with command line option -preload true or -preload false
- ***name -*** name of first stage (lines of code timed separately with `-log_view`) to
be preloaded



## Usage
```none
     PetscPreLoadBegin(PETSC_TRUE,"first stage);
       lines of code
       PetscPreLoadStage("second stage");
       lines of code
     PetscPreLoadEnd();
```





## Note
Only works in C/C++, not Fortran

Flags available within the macro.

- ***PetscPreLoadingUsed -*** true if we are or have done preloading
- ***PetscPreLoadingOn -*** true if it is CURRENTLY doing preload
- ***PetscPreLoadIt -*** 0 for the first computation (with preloading turned off it is only 0) 1 for the second
- ***PetscPreLoadMax -*** number of times it will do the computation, only one when preloading is turned on
The first two variables are available throughout the program, the second two only between the `PetscPreLoadBegin()`
and `PetscPreLoadEnd()`



## See Also
 [](ch_profiling), `PetscLogEventRegister()`, `PetscLogEventBegin()`, `PetscLogEventEnd()`, `PetscPreLoadEnd()`, `PetscPreLoadStage()`

## Level
intermediate

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/sys/logging/plog.c.html#PetscPreLoadBegin">src/sys/logging/plog.c</A>

## Examples
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex10.c.html">src/ksp/ksp/tutorials/ex10.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex27.c.html">src/ksp/ksp/tutorials/ex27.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex72.c.html">src/ksp/ksp/tutorials/ex72.c</A><BR>


---
[Edit on GitLab](https://gitlab.com/petsc/petsc/-/edit/release/src/sys/logging/plog.c)


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