petsc-3.14.5 2021-03-03
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# PetscBinaryWrite

Writes to a binary file.

### Synopsis

    PetscErrorCode  PetscBinaryWrite(int fd,const void *p,PetscInt n,PetscDataType type)

Not Collective

### Input Parameters

| fd | - the file
| p | - the buffer
| n | - the number of items to write
| type | - the type of items to read (PETSC_INT, PETSC_DOUBLE or PETSC_SCALAR)

### Notes

PetscBinaryWrite() uses byte swapping to work on all machines; the files are written using big-endian ordering to the file. On little-endian machines the numbers are converted to the big-endian format when they are written to disk. When PETSc is ./configure with --with-64-bit-indices the integers are written to the file as 64 bit integers, this means they can only be read back in when the option --with-64-bit-indices is used.

If running with __float128 precision the output is in __float128 unless one uses the -binary_write_double option

The Buffer p should be read-write buffer, and not static data. This way, byte-swapping is done in-place, and then the buffer is written to the file.

This routine restores the original contents of the buffer, after it is written to the file. This is done by byte-swapping in-place the second time.

Because byte-swapping may be done on the values in data it cannot be declared const

### See Also

PetscBinaryRead(), PetscBinaryOpen(), PetscBinaryClose(), PetscViewerBinaryGetDescriptor(), PetscBinarySynchronizedWrite(),
PetscBinarySynchronizedRead(), PetscBinarySynchronizedSeek()

### Level

advanced

### Location

src/sys/fileio/sysio.c

### Examples

src/vec/vec/tutorials/ex6.c.html
src/vec/vec/tutorials/ex6f.F90.html
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