How Big Can Arrays Be?

**MEMORY_TEST**,
a C++ program which
declares and uses a sequence of larger and larger arrays,
to see what the memory limits are on a given computer.

The program tries an increasing series of values of **N**, using
powers of 2, between limits that you set. At some point, the program
may ask for more memory than can be provided, and crash. This is one
way to find out what the memory ceiling is! The relevant power of 2
is likely to be in the 20's:

Log(N) | N |
---|---|

20 | 1,048,576 |

21 | 2,097,152 |

22 | 4,194,304 |

23 | 8,388,608 |

24 | 16,777,216 |

25 | 33,554,432 |

26 | 67,108,864 |

27 | 134,217,728 |

28 | 268,435,456 |

29 | 536,870,912 |

30 | 1,073,741,824 |

Remember that your memory is probably described in terms of bytes, but that integers and reals require 4 bytes, and double precision reals require 8 bytes.

runs the program for sizesmemory_testlog_n_minlog_n_max

The computer code and data files described and made available on this web page are distributed under the GNU LGPL license.

**MEMORY_TEST** is available in
a C version and
a C++ version and
a FORTRAN90 version and
a MATLAB version.

LINPACK_BENCH, a C++ program which measures the time needed to factor and solve a linear system.

MACHINE, a C++ library which can return various machine constants.

SUM_MILLION, a C++ program which sums the integers from 1 to 1,000,000, as a demonstration of how to rate a computer's speed;

TIMER, C++ programs which demonstrate how to compute CPU time or elapsed time.

- memory_test.cpp, the source code.
- memory_test.sh, compiles the source code.

- memory_test_g5.txt, a run of the program on a Mac G5, up to LOG(N) = 27.
- memory_test_kachina.txt, a run of the program on Kachina, an ALPHA workstation, up to LOG(N) = 27.