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Minor router1 debug log improvements

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Signed-off-by: Clifford Wolf <clifford@clifford.at>
This commit is contained in:
Clifford Wolf 2018-11-13 17:30:49 +01:00
parent 51b09f2407
commit caca485cff
2 changed files with 10 additions and 3 deletions
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10
common/router1.cc
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@ -666,12 +666,18 @@ struct Router1
WireId cursor = dst_wire;
delay_t accumulated_path_delay = 0;
delay_t last_path_delay_delta = 0;
while (1) {
auto pip = visited[cursor].pip;
if (ctx->debug) {
log(" node %s (%+.1f)\n", ctx->nameOfWire(cursor),
ctx->getDelayNS(ctx->estimateDelay(cursor, dst_wire)) - ctx->getDelayNS(accumulated_path_delay));
delay_t path_delay_delta = ctx->estimateDelay(cursor, dst_wire) - accumulated_path_delay;
log(" node %s (%+.2f %+.2f)\n", ctx->nameOfWire(cursor), ctx->getDelayNS(path_delay_delta),
ctx->getDelayNS(path_delay_delta - last_path_delay_delta));
last_path_delay_delta = path_delay_delta;
if (pip != PipId())
accumulated_path_delay += ctx->getPipDelay(pip).maxDelay();
accumulated_path_delay += ctx->getWireDelay(cursor).maxDelay();

3
docs/faq.md
View File

@ -46,7 +46,8 @@ See [archapi.md](archapi.md) for a complete reference of the architecture API.
### Delay Estimates
Each architecture must implement a `estimateDelay()` method that estimates the expected delay for a path from given `src` to `dst` wires.
*It is very important that this method slightly overestimates the expected delay.* Otherwise there will be performance issues with the router.
*It is very important that this method slightly overestimates the expected delay.* Furthermore, it should overestimate the expected delay
by a slightly larger margin for longer paths than for shorter paths. Otherwise there will be performance issues with the router.
The delays estimates returned by that method should also be as fine-grain as possible. It definitely pays off to spend some time improving the `estimateDelay()`
for your architecture once implementing small designs work.