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void equilibrilize(${float_type}* f_next,
${float_type}* f_prev,
std::size_t gid)
{
${float_type}* preshifted_f_next = f_next + gid*${layout.gid_offset()};
${float_type}* preshifted_f_prev = f_prev + gid*${layout.gid_offset()};
% for i, w_i in enumerate(descriptor.w):
preshifted_f_next[${layout.pop_offset(i)}] = ${w_i.evalf()};
preshifted_f_prev[${layout.pop_offset(i)}] = ${w_i.evalf()};
% endfor
}
void collide_and_stream( ${float_type}* f_next,
const ${float_type}* f_prev,
std::size_t gid)
{
${float_type}* preshifted_f_next = f_next + gid*${layout.gid_offset()};
const ${float_type}* preshifted_f_prev = f_prev + gid*${layout.gid_offset()};
% for i, c_i in enumerate(descriptor.c):
const ${float_type} f_curr_${i} = preshifted_f_prev[${layout.pop_offset(i) + layout.neighbor_offset(-c_i)}];
% endfor
% for i, expr in enumerate(moments_subexpr):
const ${float_type} ${expr[0]} = ${ccode(expr[1])};
% endfor
% for i, expr in enumerate(moments_assignment):
${float_type} ${ccode(expr)}
% endfor
% for i, expr in enumerate(collision_subexpr):
const ${float_type} ${expr[0]} = ${ccode(expr[1])};
% endfor
% for i, expr in enumerate(collision_assignment):
const ${float_type} ${ccode(expr)}
% endfor
% for i, expr in enumerate(collision_assignment):
preshifted_f_next[${layout.pop_offset(i)}] = f_next_${i};
% endfor
}
void velocity_momenta_boundary( ${float_type}* f_next,
const ${float_type}* f_prev,
std::size_t gid,
${float_type} velocity[${descriptor.d}])
{
${float_type}* preshifted_f_next = f_next + gid*${layout.gid_offset()};
const ${float_type}* preshifted_f_prev = f_prev + gid*${layout.gid_offset()};
% for i, c_i in enumerate(descriptor.c):
const ${float_type} f_curr_${i} = preshifted_f_prev[${layout.pop_offset(i) + layout.neighbor_offset(-c_i)}];
% endfor
% for i, expr in enumerate(moments_subexpr):
const ${float_type} ${expr[0]} = ${ccode(expr[1])};
% endfor
% for i, expr in enumerate(moments_assignment):
${float_type} ${ccode(expr)}
% endfor
% for i, expr in enumerate(moments_assignment[1:]):
${expr.lhs} = velocity[${i}];
% endfor
% for i, expr in enumerate(collision_subexpr):
const ${float_type} ${expr[0]} = ${ccode(expr[1])};
% endfor
% for i, expr in enumerate(collision_assignment):
const ${float_type} ${ccode(expr)}
% endfor
% for i, expr in enumerate(collision_assignment):
preshifted_f_next[${layout.pop_offset(i)}] = f_next_${i};
% endfor
}
void collect_moments(const ${float_type}* f,
std::size_t gid,
${float_type}& rho,
${float_type} u[${descriptor.d}])
{
const ${float_type}* preshifted_f = f + gid*${layout.gid_offset()};
% for i in range(0,descriptor.q):
const ${float_type} f_curr_${i} = preshifted_f[${layout.pop_offset(i)}];
% endfor
% for i, expr in enumerate(moments_subexpr):
const ${float_type} ${expr[0]} = ${ccode(expr[1])};
% endfor
% for i, expr in enumerate(moments_assignment):
% if i == 0:
rho = ${ccode(expr.rhs)};
% else:
u[${i-1}] = ${ccode(expr.rhs)};
% endif
% endfor
}
% if 'test_example' in extras:
void test(std::size_t nStep)
{
auto f_a = std::make_unique<${float_type}[]>(${geometry.volume*descriptor.q + 2*layout.padding()});
auto f_b = std::make_unique<${float_type}[]>(${geometry.volume*descriptor.q + 2*layout.padding()});
// buffers are padded by maximum neighbor overreach to prevent invalid memory access
${float_type}* f_prev = f_a.get() + ${layout.padding()};
${float_type}* f_next = f_b.get() + ${layout.padding()};
std::vector<std::size_t> bulk;
std::vector<std::size_t> bc;
for (int iX = 0; iX < ${geometry.size_x}; ++iX) {
for (int iY = 0; iY < ${geometry.size_y}; ++iY) {
% if descriptor.d == 2:
if (iX == 0 || iY == 0 || iX == ${geometry.size_x-1} || iY == ${geometry.size_y-1}) {
bc.emplace_back(iX*${geometry.size_y} + iY);
} else {
bulk.emplace_back(iX*${geometry.size_y} + iY);
}
% elif descriptor.d == 3:
for (int iZ = 0; iZ < ${geometry.size_z}; ++iZ) {
if (iX == 0 || iY == 0 || iZ == 0 ||
iX == ${geometry.size_x-1} || iY == ${geometry.size_y-1} || iZ == ${geometry.size_z-1}) {
bc.emplace_back(iX*${geometry.size_y*geometry.size_z} + iY*${geometry.size_z} + iZ);
} else {
bulk.emplace_back(iX*${geometry.size_y*geometry.size_z} + iY*${geometry.size_z} + iZ);
}
}
% endif
}
}
for (std::size_t iCell = 0; iCell < ${geometry.volume}; ++iCell) {
equilibrilize(f_prev, f_next, iCell);
}
const auto start = std::chrono::high_resolution_clock::now();
for (std::size_t iStep = 0; iStep < nStep; ++iStep) {
if (iStep % 2 == 0) {
f_next = f_a.get();
f_prev = f_b.get();
} else {
f_next = f_b.get();
f_prev = f_a.get();
}
for (std::size_t i = 0; i < bulk.size(); ++i) {
collide_and_stream(f_next, f_prev, bulk[i]);
}
for (std::size_t i = 0; i < bc.size(); ++i) {
equilibrilize(f_next, f_prev, bc[i]);
}
}
auto duration = std::chrono::duration_cast<std::chrono::duration<double>>(
std::chrono::high_resolution_clock::now() - start);
// calculate average rho as a basic quality check
${float_type} rho_sum = 0.0;
for (std::size_t i = 0; i < ${geometry.volume*descriptor.q}; ++i) {
rho_sum += f_next[i];
}
std::cout << "#bulk : " << bulk.size() << std::endl;
std::cout << "#bc : " << bc.size() << std::endl;
std::cout << "#steps : " << nStep << std::endl;
std::cout << std::endl;
std::cout << "MLUPS : " << nStep*${geometry.volume}/(1e6*duration.count()) << std::endl;
std::cout << "avg rho : " << rho_sum/${geometry.volume} << std::endl;
}
% endif
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