---
name: "diststream"
section: "2rheolef"
platform: "linux"
package: "librheolef-dev"
version: "7.2-4"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/diststream"
---

# diststream(2rheolef)

i/o streams in distributed environment (rheolef-7.2)

## NAME

diststream - i/o streams in distributed environment (rheolef-7.2)

## DESCRIPTION

The `idiststream` and `odiststream` classes provide a stream input and output interface for parallel and distributed codes. The main difference Recall that, with the usual `std::istream` and `std::ostream`, any i/o operation are executed on all processes: e.g. the output is printed many times. In contrast, `idiststream` and `odiststream` manage nicely the distributed environment.

For small data, e.g. `int`, `double` or `string`, a specific processor is selected for i/o operations. For large data, the i/o operations are delegated to a specific class member functions when available.

For convenience, the standard streams `cin`, `cout`, `clog` and `cerr` are extended as `din`, `dout`, `dlog` and `derr`, respectively.

## FILE SUFFIXES

Finally, optional suffix extension to the file name is automatically handled:

```
    odiststream foo('NAME', 'suffix');
```

 is similar

```
    ofstream foo('NAME.suffix').
```

 Conversely,

```
    irheostream foo('NAME','suffix');
```

 is similar to

```
    ifstream foo('NAME.suffix').
```

## FILE SEARCH

Recursive search in a directory list is provided for finding the input file. However, we look at a search path environment variable `RHEOPATH` in order to find `NAME` while the suffix is assumed. Moreover, `gzip` compressed files, ending with the `.gz` suffix are handled, and decompression is done automatically on the fly in that case.

## COMPRESSION

File compression/decompresion is handled on the fly, thanks to the `gzip` library. The data compression is assumed by default for output: it can be deactivated while opening a file by an optional argument:

```
    odiststream foo('NAME', 'suffix', io::nogz);
```

## APPEND MODE

An existing file, possibly compressed, can be reopen in `append` mode. New results will be appended at the end of an existing file:

```
    odiststream foo('NAME', 'suffix', io::app);
```

## FLUSH

The `flush` member function is nicely handled in compression mode: this feature allows intermediate results to be available during long computations. Buffers are flushed and data are available in the output file.

## IMPLEMENTATION

This documentation has been generated from file linalg/lib/diststream.h

```
class idiststream {
public:
  typedef std::size_t size_type;
// allocators/deallocators:
  idiststream();
  idiststream (std::istream& is, const communicator& comm = communicator());
  idiststream (std::string filename, std::string suffix = "",
             const communicator& comm = communicator());
  ~idiststream();
// modifiers:
  void open (std::string filename, std::string suffix = "",
             const communicator& comm = communicator());
  void close();
// accessors:
  const communicator& comm() const { return _comm; }
  bool good() const;
  operator bool() const { return good(); }
  static size_type io_proc();
```

```
};
```

```
class odiststream {
public:
  typedef std::size_t size_type;
// allocators/deallocators:
  odiststream();
  odiststream (std::string filename, std::string suffix = "",
              io::mode_type mode = io::out, const communicator& comm = communicator());
  odiststream (std::string filename,
              io::mode_type mode, const communicator& comm = communicator());
  odiststream (std::string filename, std::string suffix, const communicator& comm);
  odiststream (std::string filename, const communicator& comm);
  odiststream(std::ostream& os, const communicator& comm = communicator());
  ~odiststream();
// modifiers:
   void open (std::string filename, std::string suffix = "",
             io::mode_type mode = io::out, const communicator& comm = communicator());
   void open (std::string filename,
             io::mode_type mode, const communicator& comm = communicator());
   void open (std::string filename, std::string suffix,
             const communicator& comm);
   void open (std::string filename, const communicator& comm);
   void flush();
   void close();
// accessors:
   const communicator& comm() const { return _comm; }
   bool good() const;
   operator bool() const { return good(); }
   static size_type io_proc();
```

```
};
```

## AUTHOR

Pierre  Saramito  \<Pierre.Saramito@imag.fr\>

## COPYRIGHT

Copyright   (C)  2000-2018  Pierre  Saramito  \<Pierre.Saramito@imag.fr\> GPLv3+: GNU GPL version 3 or later  \<http://gnu.org/licenses/gpl.html\>. This  is  free  software:  you  are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law.