fj_dist2fj.h File Reference

Conversion of a LINE MAP into the arrival or service descriptor of the fork-join response-time-tail algorithm of Qiu, Perez and Harrison (IFIP Performance 2015). More...

#include <cstddef>
#include <vector>
#include "line/api/mam/map_moment.h"
#include "line/num/number.h"
#include "line/util/error.h"
#include "line/util/linalg.h"
#include "line/util/matrix.h"

Include dependency graph for fj_dist2fj.h:

Go to the source code of this file.

Classes
struct	line::fj::FjDist< T >
	Descriptor of an arrival or a service process. More...

Namespaces
namespace	line
namespace	line::fj

Enumerations
enum class	line::fj::FjProcType { line::fj::Exp = 0 , line::fj::Erlang = 1 , line::fj::HyperExp = 2 , line::fj::Map = 5 }
	The subset of ProcessType that the fork-join algorithm accepts. More...
enum class	line::fj::FjDistKind { line::fj::Arrival , line::fj::Service }
	Which of the two descriptors to build. More...

Functions
template<class T>
FjDist< T >	line::fj::fj_dist2fj (const mam::Map< T > &m, FjDistKind kind, FjProcType procType)
	Build the fork-join descriptor of a MAP.

Detailed Description

Conversion of a LINE MAP into the arrival or service descriptor of the fork-join response-time-tail algorithm of Qiu, Perez and Harrison (IFIP Performance 2015).

Templated port of matlab/src/api/fj/fj_dist2fj.m. The reference reads two scalars out of the NetworkStruct, sn.procid(ist, r) and sn.rates(ist, r); only the first is used (see the reference defects below), and it is passed here as an explicit FjProcType, so this port carries no NetworkStruct dependency.

arrival: (lambda, lambda0 = D0, lambda1 = D1, ma = phases, Ia = I) service: (mu = lambda, ST = D0, St = -D0 e, tau_st = map_pie)

At most two phases are accepted, which is the algorithm's own restriction.

REFERENCE DEFECTS in fj_dist2fj.m:

1. DEAD READ. mean_rate = sn.rates(ist, r) is computed on line 53 and never used; the rate that is returned is map_lambda of the MAP itself. Not propagated: the port does not take a rate argument at all. This matters because it is the only place the two could disagree, and the MAP is the authority.
2. mean_time = 1 / lambda is likewise computed and never used, and divides by zero for a disabled class instead of reporting it.
3. THE SERVICE BRANCH ACCEPTS MAP(2) SILENTLY. Its distribution switch rejects a two-phase MAP with an error, but only AFTER the descriptor has been filled in, and the arrival branch accepts MAP(2) explicitly. The asymmetry is intentional in the algorithm (service must be phase type), so it is reproduced: FjProcType::Map is rejected for a service process.

ARITHMETIC. map_lambda and map_pie need one linear solve each, and the exit vector is a row sum, so the whole conversion stays in the field and is instantiated at T = Rational as well as double and Real.

Definition in file fj_dist2fj.h.