On 05/31/2013 01:05 PM, Timon Gehr wrote:
> That wouldn't make any sense though, since after template expansion there is
> no
> difference between the generated version and a particular handwritten version.
That's what I'd assumed too, but there _is_ a speed difference. I'm open to
suggestions as to why.
Compare these profile results for the core inner function -- the original (even
though there's a 'New' in there somewhere):
% cumulative self self total
time seconds seconds calls s/call s/call name
93.33 4.69 4.69 4084637 0.00 0.00
_D8infected5model115__T13NewSimulationS248infected5model8StateSISS238infected5model7SeedSISS388infected5model21NewUpdateMeanFieldSISTdZ13NewSimulation19__T11UpdateStateTdZ6updateMFKC8infected5model15__T8StateSISTdZ8StateSISKxC8infected5model14__T7SeedSISTdZ7SeedSISZd
... and the newer version:
% cumulative self self total
time seconds seconds calls s/call s/call name
92.73 5.23 5.23 4078287 0.00 0.00
_D8infected5model292__T10SimulationS358infected5model18UpdateMeanFieldSISTC8infected5model15__T8StateSISTdZ8StateSISTC8infected5model164__T7SeedSISTdTAyAS3std8typecons50__T5TupleTmVAyaa2_6964TdVAyaa9_696e666c75656e6365Z5TupleTyS3std8typecons50__T5TupleTmVAyaa2_6964TdVAyaa9_696e666c75656e6365Z5TupleZ7SeedSISTydZ10Simulation17__T11UpdateStateZ163__T6updateTdTAyAS3std8typecons50__T5TupleTmVAyaa2_6964TdVAyaa9_696e666c75656e6365Z5TupleTyS3std8typecons50__T5TupleTmVAyaa2_6964TdVAyaa9_696e666c75656e6365Z5TupleZ6updateMFNbNfKC8infected5model15__T8StateSISTdZ8StateSISKxC8infected5model164__T7SeedSISTdTAyAS3std8typecons50__T5TupleTmVAyaa2_6964TdVAyaa9_696e666c75656e6365Z5TupleTyS3std8typecons50__T5TupleTmVAyaa2_6964TdVAyaa9_696e666c75656e6365Z5TupleZ7SeedSISZd
I'm not sure what, other than a change of template design, could be responsible
here. The key bits of code follow -- the original version:
mixin template UpdateState(T)
{
T update(ref StateSIS!T st, const ref SeedSIS!T sd)
{
T d = to!T(0);
static T[] sick;
sick.length = st.infected.length;
sick[] = st.infected[];
foreach(i; 0..sick.length) {
T noTransmission = to!T(1);
foreach(link; sd.network[i])
noTransmission *= (to!T(1) -
sick[link.id] * link.influence);
T getSick = (to!T(1) - sick[i]) *
(sd.susceptible[i] + (to!T(1) -
sd.susceptible[i]) * (to!T(1) - noTransmission));
T staySick = sick[i] * (to!T(1) -
sd.recover[i]);
st.infected[i] = (to!T(1) - sd.immune[i]) *
(getSick + staySick);
assert(to!T(0) <= st.infected[i]);
assert(st.infected[i] <= to!T(1));
d = max(abs(st.infected[i] - sick[i]), d);
}
return d;
}
}
... and for clarity, the StateSIS and SeedSIS classes:
class StateSIS(T)
{
T[] infected;
this(){}
this(T[] inf)
{
infected = inf;
}
auto size() @property pure const nothrow
{
return infected.length;
}
T infection() @property pure const nothrow
{
return reduce!"a+b"(to!T(0), infected);
}
}
class SeedSIS(T)
{
T[] immune;
T[] susceptible;
T[] recover;
Link!T[][] network;
this() {}
this(T[] imm, T[] sus, T[] rec, Link!T[][] net)
{
immune = imm;
susceptible = sus;
recover = rec;
network = net;
}
auto size() @property pure const nothrow
in
{
assert(immune.length == susceptible.length);
assert(immune.length == recover.length);
assert(immune.length == network.length);
}
body
{
return immune.length;
}
}
... and the "Link" template:
template Link(T)
{
alias Tuple!(size_t, "id", T, "influence") Link;
}
... and now for comparison the new versions:
mixin template UpdateState()
{
T update(T, N : L[][], L)(ref StateSIS!T st, const ref
SeedSIS!(T, N, L) sd)
{
T d = to!T(0);
static T[] sick;
sick.length = st.infected.length;
sick[] = st.infected[];
foreach(i; 0..sick.length) {
T noTransmission = to!T(1);
foreach(link; sd.network[i])
noTransmission *= (to!T(1) -
sick[link.id] * link.influence);
T getSick = (to!T(1) - sick[i]) *
(sd.susceptible[i] + (to!T(1) -
sd.susceptible[i]) * (to!T(1) - noTransmission));
T staySick = sick[i] * (to!T(1) -
sd.recover[i]);
st.infected[i] = (to!T(1) - sd.immune[i]) *
(getSick + staySick);
assert(to!T(0) <= st.infected[i]);
assert(st.infected[i] <= to!T(1));
d = max(abs(st.infected[i] - sick[i]), d);
}
return d;
}
}
class StateSIS(T)
{
T[] infected;
this() {}
this(T[] inf)
{
infected = inf;
}
auto size() @property pure const nothrow
{
return infected.length;
}
T infection() @property pure const nothrow
{
return reduce!"a+b"(to!T(0), infected);
}
}
auto stateSIS(T)(T[] inf)
{
return new StateSIS!T(inf);
}
class SeedSIS(T, Network : L[][], L)
{
T[] immune;
T[] susceptible;
T[] recover;
Network network;
this() {}
this(T[] imm, T[] sus, T[] rec, Network net)
{
immune = imm;
susceptible = sus;
recover = rec;
network = net;
}
auto size() @property pure const nothrow
in
{
assert(immune.length == susceptible.length);
assert(immune.length == recover.length);
assert(immune.length == network.length);
}
body
{
return immune.length;
}
}
auto seedSIS(T, Network : L[][], L)(T[] imm, T[] sus, T[] rec, Network
net)
{
return new SeedSIS!(T, Network, L)(imm, sus, rec, net);
}
... note that the Network that is passed to SeedSIS is still always a
Link!T[][].
