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HeAP: Successful solver convergance

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Signed-off-by: David Shah <dave@ds0.me>
This commit is contained in:
David Shah 2019-01-10 19:10:47 +00:00
parent ea56dc9d08
commit d5cfd38179
3 changed files with 115 additions and 27 deletions
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112
common/placer_heap.cc
View File

@ -59,16 +59,16 @@ template <typename T> struct EquationSystem
void add_coeff(int row, int col, T val)
{
auto &Ac = A[col];
auto &Ac = A.at(col);
// Binary search
int b = 0, e = int(Ac.size()) - 1;
while (b <= e) {
int i = (b + e) / 2;
if (Ac[i].first == row) {
Ac[i].second += val;
if (Ac.at(i).first == row) {
Ac.at(i).second += val;
return;
}
if (Ac[i].first > row)
if (Ac.at(i).first > row)
e = i - 1;
else
b = i + 1;
@ -80,19 +80,29 @@ template <typename T> struct EquationSystem
void solve(std::vector<double> &x)
{
NPNR_ASSERT(x.size() == A.size());
int nnz = std::accumulate(A.begin(), A.end(), 0,
[](int a, const std::vector<std::pair<int, T>> &vec) { return a + int(vec.size()); });
taucif_system *sys = taucif_create_system(int(rhs.size()), int(A.size()), nnz);
for (int col = 0; col < int(A.size()); col++) {
auto &Ac = A[col];
for (auto &el : Ac) {
if (col <= el.first)
taucif_set_matrix_value(sys, el.first, col, el.second);
if (col <= el.first) {
// log_info("%d %d %f\n", el.first, col, el.second);
taucif_add_matrix_value(sys, el.first, col, el.second);
}
// FIXME: in debug mode, assert really is symmetric
}
}
taucif_solve_system(sys, x.data(), rhs.data());
taucif_finalise_matrix(sys);
int result = taucif_solve_system(sys, x.data(), rhs.data());
NPNR_ASSERT(result == 0);
taucif_free_system(sys);
// for (int i = 0; i < int(x.size()); i++)
// log_info("x[%d] = %f\n", i, x.at(i));
}
};
@ -104,22 +114,38 @@ class HeAPPlacer
HeAPPlacer(Context *ctx) : ctx(ctx) {}
bool place()
{
ctx->lock();
taucif_init_solver();
place_constraints();
build_fast_bels();
seed_placement();
update_all_chains();
EquationSystem<double> es(place_cells.size(), place_cells.size());
build_equations(es, false);
solve_equations(es, false);
for (int i = 0; i < 20; i++) {
EquationSystem<double> esx(place_cells.size(), place_cells.size());
build_equations(esx, false);
// log_info("x-axis\n");
solve_equations(esx, false);
EquationSystem<double> esy(place_cells.size(), place_cells.size());
build_equations(esy, true);
// log_info("y-axis\n");
solve_equations(esy, true);
update_all_chains();
wirelen_t hpwl = total_hpwl();
log_info("Initial placer iter %d, hpwl = %d\n", i, int(hpwl));
}
ctx->unlock();
return true;
}
private:
Context *ctx;
int diameter, max_x, max_y;
int max_x = 0, max_y = 0;
std::vector<std::vector<std::vector<std::vector<BelId>>>> fast_bels;
std::unordered_map<IdString, std::tuple<int, int>> bel_types;
@ -215,7 +241,7 @@ class HeAPPlacer
max_y = std::max(max_y, loc.y);
fast_bels.at(type_idx).at(loc.x).at(loc.y).push_back(bel);
}
diameter = std::max(max_x, max_y) + 1;
nearest_row_with_bel.resize(num_bel_types, std::vector<int>(max_y + 1, -1));
nearest_col_with_bel.resize(num_bel_types, std::vector<int>(max_x + 1, -1));
for (auto bel : ctx->getBels()) {
@ -237,18 +263,29 @@ class HeAPPlacer
nc.at(x) = loc.x;
}
for (int y = loc.y; y <= max_y; y++) {
if (nr.at(y) == -1 || std::abs(loc.y - nc.at(y)) <= (y - loc.y))
if (nr.at(y) == -1 || std::abs(loc.y - nr.at(y)) <= (y - loc.y))
break;
nr.at(y) = loc.y;
}
for (int y = loc.y - 1; y >= 0; y--) {
if (nc.at(y) == -1 || std::abs(loc.y - nc.at(y)) <= (loc.y - y))
if (nr.at(y) == -1 || std::abs(loc.y - nr.at(y)) <= (loc.y - y))
break;
nc.at(y) = loc.y;
nr.at(y) = loc.y;
}
}
}
// Check if a cell has any meaningful connectivity
bool has_connectivity(CellInfo *cell)
{
for (auto port : cell->ports) {
if (port.second.net != nullptr && port.second.net->driver.cell != nullptr &&
!port.second.net->users.empty())
return true;
}
return false;
}
// Build up a random initial placement, without regard to legality
// FIXME: Are there better approaches to the initial placement (e.g. greedy?)
void seed_placement()
@ -264,13 +301,13 @@ class HeAPPlacer
int placed_cell_count = 0;
for (auto cell : sorted(ctx->cells)) {
CellInfo *ci = cell.second;
ci->udata = -1;
if (ci->bel != BelId()) {
Loc loc = ctx->getBelLocation(ci->bel);
cell_locs[cell.first].x = loc.x;
cell_locs[cell.first].y = loc.y;
cell_locs[cell.first].locked = true;
cell_locs[cell.first].global = ctx->getBelGlobalBuf(ci->bel);
} else if (ci->constr_parent == nullptr) {
if (!available_bels.count(ci->type) || available_bels.at(ci->type).empty())
log_error("Unable to place cell '%s', no Bels remaining of type '%s'\n", ci->name.c_str(ctx),
@ -282,8 +319,14 @@ class HeAPPlacer
cell_locs[cell.first].y = loc.y;
cell_locs[cell.first].locked = false;
cell_locs[cell.first].global = ctx->getBelGlobalBuf(bel);
// FIXME
if (has_connectivity(cell.second) && cell.second->type != ctx->id("SB_IO")) {
ci->udata = placed_cell_count++;
place_cells.push_back(ci);
} else {
ctx->bindBel(bel, ci, STRENGTH_STRONG);
cell_locs[cell.first].locked = true;
}
}
}
}
@ -354,6 +397,8 @@ class HeAPPlacer
ubport = &port;
}
});
NPNR_ASSERT(lbport != nullptr);
NPNR_ASSERT(ubport != nullptr);
// Add all relevant connections to the matrix
foreach_port(ni, [&](PortRef &port) {
int this_pos = cell_pos(port.cell);
@ -361,9 +406,9 @@ class HeAPPlacer
if (other == &port)
return;
int o_pos = cell_pos(other->cell);
if (o_pos == this_pos)
return; // FIXME: or clamp to 1?
double weight = 1. / (ni->users.size() * std::abs(o_pos - this_pos));
// if (o_pos == this_pos)
// return; // FIXME: or clamp to 1?
double weight = 1. / (ni->users.size() * std::max(1, std::abs(o_pos - this_pos)));
// FIXME: add criticality to weighting
// If cell 0 is not fixed, it will stamp +w on its equation and -w on the other end's equation,
@ -403,6 +448,35 @@ class HeAPPlacer
std::vector<double> vals;
std::transform(place_cells.begin(), place_cells.end(), std::back_inserter(vals), cell_pos);
es.solve(vals);
for (size_t i = 0; i < vals.size(); i++)
if (yaxis)
cell_locs.at(place_cells.at(i)->name).y = int(vals.at(i) + 0.5);
else
cell_locs.at(place_cells.at(i)->name).x = int(vals.at(i) + 0.5);
}
// Compute HPWL
wirelen_t total_hpwl()
{
wirelen_t hpwl = 0;
for (auto net : sorted(ctx->nets)) {
NetInfo *ni = net.second;
if (ni->driver.cell == nullptr)
continue;
CellLocation &drvloc = cell_locs.at(ni->driver.cell->name);
if (drvloc.global)
continue;
int xmin = drvloc.x, xmax = drvloc.x, ymin = drvloc.y, ymax = drvloc.y;
for (auto &user : ni->users) {
CellLocation &usrloc = cell_locs.at(user.cell->name);
xmin = std::min(xmin, usrloc.x);
xmax = std::max(xmax, usrloc.x);
ymin = std::min(ymin, usrloc.y);
ymax = std::max(ymax, usrloc.y);
}
hpwl += (xmax - xmin) + (ymax - ymin);
}
return hpwl;
}
};

20
common/placer_math.c
View File

@ -1,6 +1,7 @@
#include "taucs.h"
#include "placer_math.h"
#include <stdio.h>
#include <assert.h>
void taucif_init_solver() {
taucs_logfile("stdout");
@ -13,14 +14,15 @@ struct taucif_system {
struct taucif_system *taucif_create_system(int rows, int cols, int n_nonzero) {
struct taucif_system *sys = taucs_malloc(sizeof(struct taucif_system));
sys->mat = taucs_ccs_create(cols, rows, n_nonzero, TAUCS_DOUBLE | TAUCS_SYMMETRIC);
sys->mat = taucs_ccs_create(cols, rows, n_nonzero, TAUCS_DOUBLE | TAUCS_SYMMETRIC | TAUCS_LOWER);
// Internal pointers
sys->ccs_i = 0;
sys->ccs_col = -1;
return sys;
};
void taucif_set_matrix_value(struct taucif_system *sys, int row, int col, double value) {
void taucif_add_matrix_value(struct taucif_system *sys, int row, int col, double value) {
assert(sys->ccs_col <= col);
while(sys->ccs_col < col) {
sys->mat->colptr[++sys->ccs_col] = sys->ccs_i;
}
@ -28,16 +30,26 @@ void taucif_set_matrix_value(struct taucif_system *sys, int row, int col, double
sys->mat->values.d[sys->ccs_i++] = value;
}
void taucif_solve_system(struct taucif_system *sys, double *x, double *rhs) {
void taucif_finalise_matrix(struct taucif_system *sys) {
sys->mat->colptr[++sys->ccs_col] = sys->ccs_i;
#if 0
taucs_ccs_write_ijv(sys->mat, "matrix.ijv");
#endif
}
int taucif_solve_system(struct taucif_system *sys, double *x, double *rhs) {
// FIXME: preconditioner, droptol??
taucs_ccs_matrix* precond_mat = taucs_ccs_factor_llt(sys->mat, 1e-3, 0);
if (precond_mat == NULL)
return -1;
// FIXME: itermax, convergetol
int cjres = taucs_conjugate_gradients(sys->mat, taucs_ccs_solve_llt, precond_mat, x, rhs, 1000, 1e-6);
taucs_ccs_free(precond_mat);
return 0;
}
void taucif_free_system(struct taucif_system *sys) {
taucs_ccs_free(sys->mat);
taucs_free(sys->mat);
taucs_free(sys);
}

6
common/placer_math.h
View File

@ -30,9 +30,11 @@ struct taucif_system;
extern struct taucif_system *taucif_create_system(int rows, int cols, int n_nonzero);
extern void taucif_set_matrix_value(struct taucif_system *sys, int row, int col, double value);
extern void taucif_add_matrix_value(struct taucif_system *sys, int row, int col, double value);
extern void taucif_solve_system(struct taucif_system *sys, double *x, double *rhs);
extern void taucif_finalise_matrix(struct taucif_system *sys);
extern int taucif_solve_system(struct taucif_system *sys, double *x, double *rhs);
extern void taucif_free_system(struct taucif_system *sys);