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Fix auto Fmax overconstraining during update_budget()

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This commit is contained in:
Eddie Hung 2018-07-27 23:46:05 -07:00
parent 0bbe309a26
commit 0be236ce05
1 changed files with 19 additions and 15 deletions
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34
common/timing.cc
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@ -143,18 +143,6 @@ void assign_budget(Context *ctx)
UpdateMap updates; UpdateMap updates;
delay_t min_slack = compute_min_slack(ctx, &updates, nullptr); delay_t min_slack = compute_min_slack(ctx, &updates, nullptr);
// If user has not specified a frequency, adjust the target frequency dynamically
// TODO(eddieh): Tune these factors
if (!ctx->user_freq) {
if (min_slack < 0)
ctx->target_freq = 1e12 / (default_slack - 0.95 * min_slack);
else
ctx->target_freq = 1e12 / (default_slack - 1.2 * min_slack);
if (ctx->verbose)
log_info("minimum slack for this assign = %d, target Fmax for next update = %.2f MHz\n", min_slack,
ctx->target_freq / 1e6);
}
// Update the budgets // Update the budgets
for (auto &net : ctx->nets) { for (auto &net : ctx->nets) {
for (size_t i = 0; i < net.second->users.size(); ++i) { for (size_t i = 0; i < net.second->users.size(); ++i) {
@ -180,6 +168,18 @@ void assign_budget(Context *ctx)
} }
} }
// If user has not specified a frequency, adjust the target frequency dynamically
// TODO(eddieh): Tune these factors
if (!ctx->user_freq) {
if (min_slack < 0)
ctx->target_freq = 1e12 / (default_slack - 0.95 * min_slack);
else
ctx->target_freq = 1e12 / (default_slack - 1.2 * min_slack);
if (ctx->verbose)
log_info("minimum slack for this assign = %d, target Fmax for next update = %.2f MHz\n", min_slack,
ctx->target_freq / 1e6);
}
log_info("Checksum: 0x%08x\n", ctx->checksum()); log_info("Checksum: 0x%08x\n", ctx->checksum());
} }
@ -215,12 +215,16 @@ void update_budget(Context *ctx)
} }
} }
// If user has not specified a frequency, adjust the frequency dynamically: // If user has not specified a frequency, adjust the target frequency dynamically
// TODO(eddieh): Tune these factors
if (!ctx->user_freq) { if (!ctx->user_freq) {
delay_t default_slack = delay_t(1.0e12 / ctx->target_freq); delay_t default_slack = delay_t(1.0e12 / ctx->target_freq);
ctx->target_freq = 1e12 / (default_slack - min_slack); if (min_slack < 0)
ctx->target_freq = 1e12 / (default_slack - 0.95 * min_slack);
else
ctx->target_freq = 1e12 / (default_slack - 1.2 * min_slack);
if (ctx->verbose) if (ctx->verbose)
log_info("minimum slack for this update = %d, target Fmax for next update = %.2f MHz\n", min_slack, log_info("minimum slack for this assign = %d, target Fmax for next update = %.2f MHz\n", min_slack,
ctx->target_freq / 1e6); ctx->target_freq / 1e6);
} }
} }