Examples

Note that we have included the SPRNG header file sprng.h at the beginning.

First we initialize a random number stream, if this is a new run. The value of the seed is defined to be 985456376. We call print_sprng immediately after initialization so that we can record the particular stream we obtained, for later reference.

If this is the continuation of a previous run, then we read in the state of a stream from the input file, and unpack it to obtain a random number stream.

sprng is next called to return double precision random numbers in [0,1).

Finally, we pack the state of the stream into an array and store the contents of this array into the output file.

Code:

Simple Interface		Default/Pointer Checking Interface
C	FORTRAN	C	FORTRAN

Compilation: Example compilation on the SGI Power Challenge

cc -64 -I../include -o checkpoint-simple checkpoint-simple.c -L../lib -lsprng -lgmp

Output:

sprng/EXAMPLES:sif% checkpoint
Enter name of file to store final state of the stream:
temp
Enter name of file to read from:
        (enter 9 for a new run)
9
 Printing 5 random numbers in [0,1): 
1  0.707488
2  0.664048
3  0.005616
4  0.872626
5  0.691387
sprng/EXAMPLES:sif% checkpoint
Enter name of file to store final state of the stream:
temp
Enter name of file to read from:
        (enter 9 for a new run)
temp
 Printing 5 random numbers in [0,1): 
1  0.280336
2  0.005228
3  0.533545
4  0.710482
5  0.891603

8. message_mpi

Note that we have included the SPRNG and MPI header files at the beginning.

First we initialize MPI.

We then initialize a random number stream on process 0. The value of the seed is defined to be 985456376. We call print_sprng immediately after initialization so that we can record the particular stream we obtained, for later reference.

sprng is next called by process 0 to return double precision random numbers in [0,1).

Process 0 then packs the state of the stream into an array and sends it to process 1, which unpacks it and prints a few more random numbers from that stream. In this process, the original default stream on process 1 is over-written by the unpacked stream.

Code:

Simple Interface		Default/Pointer Checking Interface
C	FORTRAN	C	FORTRAN

Compilation: Example compilation on the SGI Power Challenge

cc -64 -I../include -o message-simple_mpi message-simple_mpi.c -L../lib -lsprng -lgmp -L/usr/lib64 -lmpi

Output:

sprng/EXAMPLES:sif% mpirun -np 2 message-simple_mpi
Process 0: Print information about stream:

Linear Congruential Generator

        seed = 985456376, prime = 11863279
        multiplier = 44485709377909

Process 0: Print 2 random numbers in [0,1):
Process 0: 0.707488
Process 0: 0.664048
 Process 0 sends stream to process 1
 Process 1 has received the packed stream
Process 1: Print information about stream:

Linear Congruential Generator

        seed = 985456376, prime = 11863279
        multiplier = 44485709377909

 Process 1 prints 2 numbers from received stream:
Process 1: 0.005616
Process 1: 0.872626

9. 2streams_mpi

Note that we have included the SPRNG and MPI header files at the beginning.

First we initialize MPI and determine the number of processes and the rank of the local process.

We then initialize a random number stream. The value of the seed is defined to be 985456376. We shall have two streams per process, but is only one of these streams will be distinct. The other stream will be identical on each process. This is useful in situations in which we would like all the processes to take the same decision based on a random number. Thus the number of distinct streams is one more than the total number of processor, resulting in nstreams = nprocs + 1. For the distinct stream on each process, we initialize it with stream number as the rank of the local process, myid. The common stream is initialized with the stream number nprocs.

sprng is next called for each stream. It returns a double precision random numbers in [0,1) with the stream ID as its argument.

Finally, we free the memory used to store the states of the two streams by calls to free_sprng.

Code:

Simple Interface		Default/Pointer Checking Interface
Not Available		C	FORTRAN

Compilation: Example compilation on the SGI Power Challenge

cc -64 -I../include -o 2streams_mpi 2streams_mpi.c -L../lib -lsprng -lgmp -L/usr/lib64 -lmpi

Output:

sprng/EXAMPLES:sif% mpirun -np 2 2streams_mpi
Process 0: Print information about new stream

Linear Congruential Generator

        seed = 985456376, prime = 11863279
        multiplier = 44485709377909

Process 0: This stream is identical on all processes

Linear Congruential Generator

        seed = 985456376, prime = 11863253
        multiplier = 44485709377909

Process 0, random number (distinct stream) 1: 0.707488
Process 0, random number (distinct stream) 2: 0.664048
Process 0, random number (shared stream) 1: 0.700906
Process 0, random number (shared stream) 2: 0.602204
Process 1: Print information about new stream

Linear Congruential Generator

        seed = 985456376, prime = 11863259
        multiplier = 44485709377909

Process 1: This stream is identical on all processes

Linear Congruential Generator

        seed = 985456376, prime = 11863253
        multiplier = 44485709377909

Process 1, random number (distinct stream) 1: 0.991442
Process 1, random number (distinct stream) 2: 0.150989
Process 1, random number (shared stream) 1: 0.700906
Process 1, random number (shared stream) 2: 0.602204

10. spawn

Note that we have included the SPRNG header file at the beginning.

First we initialize a random number stream. The value of the seed is defined to be 985456376. Since there is only one stream, the number of streams nstreams = 1 and the stream number streamnum = 0. stream stores the returned ID of the initialized stream. We call print_sprng immediately after initialization so that we can record the particular stream we obtained, for later reference.

sprng is next called to return double precision random numbers in [0,1), with the stream ID as its argument.

We next spawn two streams from stream. Their ID's are stored in an array allocated by sprng. The variable new points to this array. We print information about the newly spawned streams, and then print a few random numbers from the second stream spawned.

Finally, we free the memory used to store the states of the streams by calls to free_sprng.

Code:

Simple Interface		Default/Pointer Checking Interface
Not Available		C	FORTRAN

Compilation: Example compilation on the SGI Power Challenge

cc -64 -I../include -o spawn spawn.c -L../lib -lsprng -lgmp

Output:

sprng/EXAMPLES:sif% spawn
 Print information about stream:

Linear Congruential Generator

        seed = 985456376, prime = 11863279
        multiplier = 44485709377909

 Printing 2 random numbers in [0,1):
0.707488
0.664048
 Spawned two streams
 Information on first spawned stream:

Linear Congruential Generator

        seed = 985456376, prime = 11863259
        multiplier = 44485709377909

 Information on second spawned stream:

Linear Congruential Generator

        seed = 985456376, prime = 11863253
        multiplier = 44485709377909

 Printing 2 random numbers from second spawned stream:
0.700906
0.602204

11. invalid_ID

Note that we have included the SPRNG header file sprng.h at the beginning. We have also defined the macroCHECK_POINTERS before including the SPRNG header file in order to invoke the interface with pointer checking.

First we initialize a random number stream. The value of the seed is defined to be 985456376. Since there is only one stream, the number of streams nstreams = 1 and the stream number streamnum = 0. stream stores the returned ID of the initialized stream. We call print_sprng immediately after initialization so that we can record the particular stream we obtained, for later reference.

sprng is next called to return double precision random numbers in [0,1), with the stream ID as its argument.

Finally, we free the memory used to store the state of the stream by a call to free_sprng.

we then try to use the freed stream again, which is an incorrect usage. sprng returns -1.0 due to the invalid stream being passed as an argument.

Code:

Simple Interface		Pointer Checking Interface
Not Available		C	FORTRAN

Compilation: Example compilation on the SGI Power Challenge

cc -64 -I../include -o invalid_ID invalid_ID.c -L../lib -lsprng -lgmp

Output:

sprng/EXAMPLES:sif% invalid_ID
Print information about random number stream:

Linear Congruential Generator

        seed = 985456376, prime = 11863279
        multiplier = 44485709377909

Printing 3 random numbers in [0,1):
0.707488
0.664048
0.005616
Expect a SPRNG error message on the use of an invalid stream ID
ERROR: Invalid generator ID 10014ed8
sprng returns -1.000000 on being given an invalid stream ID

12. convert

Note that we have included the SPRNG header file at the beginning. We have also defined the macroSIMPLE_SPRNG before including the SPRNG header file in order to invoke the simple interface. We define the macro myrandom to sprng after including the SPRNG header. This replaces the former function call by calls to SPRNG instead.

We then add statements to initialize SPRNG.

Code:

Simple Interface		Default/Pointer Checking Interface
C	FORTRAN	Not Available

Compilation: Example compilation on the SGI Power Challenge

cc -64 -I../include convert.c -L../lib -lsprng -lgmp

Note: In the code provided with SPRNG, users need to define the macro CONVERT in order to get this converted code.

Output:

sprng/EXAMPLES:sif% a.out
Print information about random number stream:

Linear Congruential Generator

        seed = 985456376, prime = 11863279
        multiplier = 44485709377909

Printing 3 random numbers in [0,1):
0.707488
0.664048
0.005616

13. subroutine

Note that we have included the SPRNG header file sprng_f.h at the beginning. We have also included this header file in the subroutine sub1. If we wished to define a macro for use by SPRNG, we need only do it once in any file, before the first time a SPRNG header is included.

Subroutine sub1 is then called, which makes calls to sprng.

Code:

Simple Interface		Default/Pointer Checking Interface
Not Available		FORTRAN

Compilation: Example compilation on the SGI Power Challenge

f77 -64 -I../include -DPOINTER_SIZE=8 subroutinef.F -L../lib -lsprng -lgmp 

Output:

sprng/EXAMPLES:sif% a.out
 Printing information about new stream

Linear Congruential Generator

        seed = 985456376, prime = 11863279
        multiplier = 44485709377909

 Printing 3 double precision numbers in [0,1): 
     1   0.7074876636340832
     2   0.6640484187971047
     3   0.0056156511936152

14. pi-simple

The user specifies the number of samples to be generated on the square. The final state of the computations is stored in a file specified by the user. The user can restart the computations by reading from this file in subsequent runs. The user should also specify whether the current run is a new one (in which case a new random number stream is initialized) or an old one (in which case the state of the random number stream is read from a file).

Note that we have included the SPRNG header file at the beginning. We have also defined the macroSIMPLE_SPRNG before including the SPRNG header file in order to invoke the simple interface.

The function initialize is then called to take suitable actions based on the information input by the user. A new run involves initializing a random number stream. In a continuation of a previous run, the state of the random number stream is read from a file whose name is input by the user. The final state of the computations is also written into this file. The user should also input the number of samples to be generated in this run. In a new run, make_sprng_seed is called to produce a seed based on system date and time information.

Next the function count_in_circle is called, which generates points on a square of side 2. The number of points that fall on a circle of unit radius inscribed within this square is returned by this function.

We then estimate PI as four times the proportion of points that fall within the circle inscribed in the square.

Finally we call the function save_state to save the state of the random number stream, the cumulative number of sample points generated in all the runs, and the cumulative number of sample points that lie within the inscribed circle in all the runs.

Code:

C	FORTRAN

Compilation: Example compilation on the SGI Power Challenge

cc -64 -I../include -o pi-simple pi-simple.c -L../lib -lsprng -lgmp

Output:

sprng/EXAMPLES:sif% pi-simple
Enter 9 for a new run, or 2 for the continuation of an old run:
9
Enter name of file to store final state of the stream:
temp
Enter number of new samples:
10000

Linear Congruential Generator

        seed = 437891907, prime = 11863279
        multiplier = 44485709377909

pi is estimated as 3.1227999999999998 from 10000 samples.
        Error = 0.0187927, standard error = 0.0164218
sprng/EXAMPLES:sif% pi-simple
Enter 9 for a new run, or 2 for the continuation of an old run:
2
Enter name of file to store final state of the stream:
temp
Enter number of new samples:
5000
pi is estimated as 3.1165333333333334 from 15000 samples.
        Error = 0.0250593, standard error = 0.0134084

15. pi-simple_mpi

First we initialize MPI and call the function initialize to initialize a random number stream. If this is the continuation of a previously checkpointed run, then process 0 reads the previous state and passes to to each process.

Next we divide the number of samples to be generated among all the processes and then call the function count_in_circle as in the sequential case. We then sum the number of points that fall within the circle across all the processes by a call to MPI_REDUCE and estimate PI as four times the proportion of points that fall within this circle inscribed in the square.

Finally we call the function save_state to save the state of the random number stream, the cumulative number of sample points generated in all the runs, and the cumulative number of sample points that lie within the inscribed circle in all the runs. Each process passes the state of its stream to process 0, which then saves it to a file.

Code:

C

Compilation: Example compilation on the SGI Power Challenge

cc -64 -I../include -o pi-simple pi-simple.c -L../lib -lsprng -lgmp

Compilation: Example compilation on the SGI Power Challenge

cc -64 -I../include -o pi-simple_mpi pi-simple_mpi.c -L../lib -lsprng -lgmp -L/usr/lib64 -lmpi

Output:

sprng/EXAMPLES:sif% mpirun -np 2 pi-simple_mpi 
Enter 9 for a new run, or 2 for the continuation of an old run:
9
Enter name of file to store final state of the stream:
temp
Enter number of new samples:
5000

Linear Congruential Generator

Linear Congruential Generator

        seed = 42578755, prime = 11863279
        multiplier = 44485709377909


        seed = 42578755, prime = 11863259
        multiplier = 44485709377909

pi is estimated as 3.1568000000000001 from 5000 samples.
        Error = 0.0152073, standard error = 0.023224