dynpro.h

经典numerical receip 配套代码

VecInt dynpro(const VecInt &nstate,
	Doub cost(Int jj, Int kk, Int ii)) {
	const Doub BIG = 1.e99;
	static const Doub EPS=numeric_limits<Doub>::epsilon();
	Int i, j ,k, nstage = nstate.size() - 1;
	Doub a,b;
	VecInt answer(nstage+1);
	if (nstate[0] != 1 || nstate[nstage] != 1)
		throw("One state allowed in first and last stages.");
	Doub **best = new Doub*[nstage+1];
	best[0] = new Doub[nstate[0]];
	best[0][0] = 0.;
	for (i=1; i<=nstage; i++) {
		best[i] = new Doub[nstate[i]];
		for (k=0; k<nstate[i]; k++) {
			b = BIG;
			for (j=0; j<nstate[i-1]; j++) {
				if ((a = best[i-1][j] + cost(j,k,i-1)) < b) b = a;
			}
			best[i][k] = b;
		}
	}
	answer[nstage] = answer[0] = 0;
	for (i=nstage-1; i>0; i--) {
		k = answer[i+1];
		b = best[i+1][k];
		for (j=0; j<nstate[i]; j++) {
			Doub temp = best[i][j] + cost(j,k,i);
			if (fabs(b - temp) <= EPS*fabs(temp)) break;
		}
		answer[i] = j;
	}
	for (i=nstage; i>=0; i--) delete [] best[i];
	delete [] best;
	return answer;
}