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#include <igraph.h>
int main(void) {
igraph_matrix_t m;
igraph_vector_t x, y, z;
igraph_real_t xz, xx;
igraph_vector_init_real(&x, 3, 1.0, 2.0, 3.0);
igraph_vector_init_real(&y, 4, 4.0, 5.0, 6.0, 7.0);
igraph_vector_init_real(&z, 3, -1.0, 0.0, 0.5);
igraph_matrix_init(&m, 4, 3);
MATRIX(m, 0, 0) = 1;
MATRIX(m, 0, 1) = 2;
MATRIX(m, 0, 2) = 3;
MATRIX(m, 1, 0) = 2;
MATRIX(m, 1, 1) = 3;
MATRIX(m, 1, 2) = 4;
MATRIX(m, 2, 0) = 3;
MATRIX(m, 2, 1) = 4;
MATRIX(m, 2, 2) = 5;
MATRIX(m, 3, 0) = 4;
MATRIX(m, 3, 1) = 5;
MATRIX(m, 3, 2) = 6;
/* Compute 2 m.x + 3 y and store it in y. */
igraph_blas_dgemv(/* transpose= */ 0, /* alpha= */ 2, &m, &x, /* beta= */ 3, &y);
igraph_vector_print(&y);
/* Compute the squared norm of x, as well as the dor product of x and z. */
igraph_blas_ddot(&x, &x, &xx);
igraph_blas_ddot(&x, &z, &xz);
printf("x.x = %g, x.z = %g\n", xx, xz);
igraph_matrix_destroy(&m);
igraph_vector_destroy(&z);
igraph_vector_destroy(&y);
igraph_vector_destroy(&x);
return 0;
}
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