public static int ContractByBest(nmsimplex_state_t state, int best, PZMath_vector xc,
PZMath_multimin_function f)
{
/* Function contracts the simplex in respect to
best valued corner. That is, all corners besides the
best corner are moved. */
/* the xc vector is simply work space here */
PZMath_matrix x1 = state.x1;
PZMath_vector y1 = state.y1;
int i, j;
double newval;
for (i = 0; i < x1.RowCount; i++)
{
if (i != best)
{
for (j = 0; j < x1.ColumnCount; j++)
{
newval = 0.5 * (x1[i, j] + x1[best, j]);
x1[i, j] = newval;
}
/* evaluate function in the new point */
x1.CopyRow2(i, xc);
newval = f.FN_EVAL(xc);
y1[i] = newval;
}
}
return PZMath_errno.PZMath_SUCCESS;
}
public int Init(PZMath_multimin_function f, PZMath_vector x, PZMath_vector step_size)
{
this.f = f;
this.x.MemCopyFrom(x);
return type.init(state, this.f, this.x, out this.size, step_size);
}
public static int Init(object vstate, PZMath_multimin_function f, PZMath_vector x,
out double size, PZMath_vector step_size)
{
int i;
double val;
PZMath_vector xtemp = (vstate as nmsimplex_state_t).ws1;
/* first point is the original x0 */
val = f.FN_EVAL(x);
(vstate as nmsimplex_state_t).x1.SetRow(0, x);
(vstate as nmsimplex_state_t).y1[0] = val;
/* following points are initialized to x0 + step_size */
for (i = 0; i < x.size; i++)
{
xtemp.MemCopyFrom(x);
val = xtemp[i] + step_size[i];
xtemp[i] = val;
val = f.FN_EVAL(xtemp);
(vstate as nmsimplex_state_t).x1.SetRow(i + 1, xtemp);
(vstate as nmsimplex_state_t).y1[i + 1] = val;
}
/* Initialize simplex size */
size = Size (vstate as nmsimplex_state_t);
return PZMath_errno.PZMath_SUCCESS;
}
public static double MoveCorner(double coeff, nmsimplex_state_t state, int corner,
PZMath_vector xc, PZMath_multimin_function f)
{
/* moves a simplex corner scaled by coeff (negative value represents
mirroring by the middle point of the "other" corner points)
and gives new corner in xc and function value at xc as a
return value
*/
PZMath_matrix x1 = state.x1;
int i, j;
double newval, mp;
if (x1.RowCount < 2)
{
PZMath_errno.ERROR ("nmsimplex::MoveCorner(), simplex cannot have less than two corners!", PZMath_errno.PZMath_FAILURE);
}
for (j = 0; j < x1.ColumnCount; j++)
{
mp = 0.0;
for (i = 0; i < x1.RowCount; i++)
{
if (i != corner)
{
mp += (x1[i, j]);
}
}
mp /= (double) (x1.RowCount - 1);
newval = mp - coeff * (mp - x1[corner, j]);
xc[j] = newval;
}
newval = f.FN_EVAL(xc);
return newval;
}
public static int Iterate(object vstate, PZMath_multimin_function f,
PZMath_vector x, out double size, out double fval)
{
/* Simplex iteration tries to minimize function f value */
/* Includes corrections from Ivo Alxneit <*****@*****.**> */
/* xc and xc2 vectors store tried corner point coordinates */
PZMath_vector xc = (vstate as nmsimplex_state_t).ws1;
PZMath_vector xc2 = (vstate as nmsimplex_state_t).ws2;
PZMath_vector y1 = (vstate as nmsimplex_state_t).y1;
PZMath_matrix x1 = (vstate as nmsimplex_state_t).x1;
int n = y1.size;
int i;
int hi = 0, s_hi = 0, lo = 0;
double dhi, ds_hi, dlo;
int status;
double val, val2;
/* get index of highest, second highest and lowest point */
dhi = ds_hi = dlo = y1[0];
for (i = 1; i < n; i++)
{
val = y1[i];
if (val < dlo)
{
dlo = val;
lo = i;
}
else if (val > dhi)
{
ds_hi = dhi;
s_hi = hi;
dhi = val;
hi = i;
}
else if (val > ds_hi)
{
ds_hi = val;
s_hi = i;
}
}
/* reflect the highest value */
val = MoveCorner (-1.0, vstate as nmsimplex_state_t, hi, xc, f);
if (val < y1[lo])
{
/* reflected point becomes lowest point, try expansion */
val2 = MoveCorner (-2.0, vstate as nmsimplex_state_t, hi, xc2, f);
if (val2 < y1[lo])
{
x1.SetRow(hi, xc2);
y1[hi] = val2;
}
else
{
x1.SetRow(hi, xc);
y1[hi] = val;
}
}
/* reflection does not improve things enough */
else if (val > y1[s_hi])
{
if (val <= y1[hi])
{
/* if trial point is better than highest point, replace
highest point */
x1.SetRow(hi, xc);
y1[hi] = val;
}
/* try one dimensional contraction */
val2 = MoveCorner (0.5, vstate as nmsimplex_state_t, hi, xc2, f);
if (val2 <= y1[hi])
{
x1.SetRow(hi, xc2);
y1[hi] = val2;
}
else
{
/* contract the whole simplex in respect to the best point */
status = ContractByBest (vstate as nmsimplex_state_t, lo, xc, f);
if (status != 0)
{
PZMath_errno.ERROR("nmsimplex::Iterate(), nmsimplex_contract_by_best failed", PZMath_errno.PZMath_FAILURE);
}
}
}
else
{
/* trial point is better than second highest point.
Replace highest point by it */
x1.SetRow(hi, xc);
y1[hi] = val;
}
/* return lowest point of simplex as x */
lo = y1.MinIndex();
x1.CopyRow2(lo, x);
fval = y1[lo];
/* Update simplex size */
size = Size (vstate as nmsimplex_state_t);
return PZMath_errno.PZMath_SUCCESS;
}
public static void TestMultiminNMSimplex()
{
int np = 2;
TestMultiminNMSimplexParms parms = new TestMultiminNMSimplexParms(1.0, 2.0);
PZMath_multimin_fminimizer_type T = new PZMath_multimin_fminimizer_type();
T.Init("PZMath_multimin_fminimizer_nmsimplex");
PZMath_multimin_fminimizer s = new PZMath_multimin_fminimizer();
/* Initial vertex size vector */
PZMath_vector ss = new PZMath_vector(np);
PZMath_vector x;
PZMath_multimin_function minex_func = new PZMath_multimin_function();
int iter = 0, i;
int status;
double size;
/* Set all step sizes to 1 */
ss.SetAll(1.0);
/* Starting point */
x = new PZMath_vector(np);
x[0] = 5.0;
x[1] = 7.0;
/* Initialize method and iterate */
minex_func.f = new multimin_function(my_f);
minex_func.n = np;
minex_func.parms = parms;
s.Alloc(T, np);
s.Init(minex_func, x, ss);
do
{
iter++;
status = s.Iterate();
if (status > 0)
break;
size = s.Size();
status = s.TestSize (size, 1e-2);
if (status == 0)
{
System.Console.WriteLine ("converged to minimum at");
}
System.Console.Write (iter + " ");
for (i = 0; i < np; i++)
{
System.Console.Write (s.x[i] + " ");
}
System.Console.WriteLine ("f() = " + s.fval + " size = " + size);
}
while (status == -2 && iter < 100);
System.Console.ReadLine();
}
