MEMORY_TEST
How Big Can Arrays Be?

MEMORY_TEST is a FORTRAN90 program, using integer, single precision real and double precision real arithmetic, which declares and uses a sequence of larger and larger arrays, to see how big vectors can be in a program.

The program tries an increasing series of values of N, using powers of 2. You can set an internal value of N_LOG_MAX in order to limit the maximum value of N to be checked. This can be handy, since sometimes when you ask for a really big array, instead of failing immediately, the program simply bogs down in some sort of infinite muddle.

Log(N)	N
0	1
1	2
2	4
3	8
4	16
5	32
6	64
7	128
8	256
9	512
10	1,024
11	2,048
12	4,096
13	8,192
14	16,384
15	32,768
16	65,536
17	131,072
18	262,144
19	524,288
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

Usage:

memory_test

runs the program

Related Data and Programs:

LINPACK_BENCH is a FORTRAN90 benchmark program which measures the time needed to factor and solve a linear system.

MACHINE is a FORTRAN90 library which can return various machine constants.

MATMUL is an executable FORTRAN90 program whichis an interactive matrix multiplication benchmark program.

MDBNCH is an executable FORTRAN77 program which is a benchmark code for a molecular dynamics calculation.

MEMORY_TEST is also available in a C++ version and a MATLAB version.

TIMER is a set of FORTRAN90 example programs that demonstrate how to compute CPU time or elapsed time.

Source Code:

• memory_test.f90, the source code.
• memory_test.csh, commands to compile the source code.

Examples and Tests:

• memory_test_output_aspen.txt, a run of the program on Aspen, a SUN workstation, up to LOG(N) = 27.
• memory_test_output_chili.txt, a run of the program on Chili, an ALPHA workstation, up to LOG(N) = 27.
• memory_test_output_class15.txt, a run of the program on Class15, an ALPHA workstation, up to LOG(N) = 27.
• memory_test_output_g5.txt, a run of the program on an Apple G5, up to LOG(N) = 27.
• memory_test_output_phoenix.txt, a run of the program on (one node of) Phoenix, a LINUX cluster, up to LOG(N) = 26.
• memory_test_output_quadrature.txt, a run of the program on Quadrature, a LINUX workstation, up to LOG(N) = 27.

List of Routines:

• MAIN is the main program for MEMORY_TEST.
• I4VEC_MEMORY_TEST declares and uses an I4VEC of size N.
• R4VEC_MEMORY_TEST declares and uses an R4VEC of size N.
• R8VEC_MEMORY_TEST declares and uses an R8VEC of size N.
• REAL_TIME returns the real time in seconds.
• TIMESTAMP prints the current YMDHMS date as a time stamp.

You can go up one level to the FORTRAN90 source codes.