Calling a C Function Within Maple 6

© 2000 Waterloo Maple Inc.

This brief example highlights Maple6's capabilities to call a C funtion from within Maple 6.

The External Code

First, we define a C procedure to multiply two matrices A and B, which stores the result into the matrix C.

Arithmetic is done modulo the prime integer p, which should be less than

void multiply( int *A, int *B, int *C, int I, int J, int K, int p )
{
int i, j, k;
int t;
for( i = 0; i < I; i++ )
for( k = 0; k < K; k++ ) {
t = 0;
for( j = 0; j < J; j++ ) {

t += A[i*J+j] * B[j*K+k];

t %= p; if (t<0) t += p;

}

C[i*K+k] = t;
}
}

This code needs to be compiled and turned into a shared library. Under Windows, we need to produce a DLL with this code. Let's call this DLL "MulMat.dll"

The Maple Wrapper

Next, we define a Maple wrapper, which we will use to call into the external DLL

> multiplyMatrixModp := define_external(
'multiply',
a::ARRAY(1..i,1..j,integer[4]),
b::ARRAY(1..j,1..k,integer[4]),
c::REF(ARRAY(1..i,1..k,integer[4]),RETURN_ONLY),
i::integer[4],
j::integer[4],
k::integer[4],
p::integer[4],
LIB="MulMat.dll"):

Calling the External Function

We will now use the external code that we have developed, compiled and turned into a DLL. We want to multiply two 100x100 matrices with entries from the integers modulo 17.

> p := 17;

> A := Matrix(100,100,(i,j)->i+j mod p,datatype=integer[4],order=C_order):

> B := Matrix(100,100,(i,j)->i*j mod p,datatype=integer[4],order=C_order):

> multiplyMatrixModp(A,B,C,100,100,100,p):

The last command converted the input arguments to a format that can be passed to C code directly, called the external C function 'multiply' from the DLL 'MulMat.dll' and returned the result in the variable C. Because the internal datastructure used for matrices (using C_order) is very close to what C uses, the conversion overhead was minimal.