struct v2
    {
    double el[2];
    };

struct v4
    {
    struct v2 el[2];
    };

struct m22
    {
    double el[2][2];
    };

struct m24
    {
    struct m22 el[2];
    };

struct m42
    {
    struct m22 el[2];
    };

struct m44
    {
    struct m22 A;
    struct m22 B;
    struct m22 C;
    struct m22 D;
    };

struct triblock22
    {
    struct v2 c[xm-1];
    struct m22 a[xm];
    struct v2 b[xm-1];
    };

struct triblock24
    {
    struct m22 c[xm-1];
    struct m24 a[xm];
    struct m22 b[xm-1];
    };

struct triblock44
    {
    struct m42 c[xm-1];
    struct m44 a[xm];
    struct m42 b[xm-1];
    };

struct kvec2
    {
    struct v2 el[xm];
    };

struct kvec4
    {
    struct v4 el[xm];
    };

struct gvec2
    {
    struct v2 el[xm-1];
    };

struct gvec4
    {
    struct m42 el[xm-1];
    };

struct collmat
    {
    struct triblock22  CF;
    struct triblock24  C[ym-2];
    struct triblock24  CL;
    struct triblock22  AF;
    struct triblock44  A[ym-1];
    struct triblock22  AL;
    struct triblock24  BF;
    struct triblock24  B[ym-2];
    struct triblock22  BL;
    };

struct collvec
    {
    struct kvec2 F;
    struct kvec4 M[ym-1];
    struct kvec2 L;
    };

struct corner_element_bcs
    {
    double el[4][2][2][2];
    };

struct EW_element_bcs
    {
    double el[ym-2][4][2][2];
    };

struct NS_element_bcs
    {
    double el[xm-2][4][2][2];
    };