Fix assertion failure in NullEvent::setCompute with small G values#17
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Fix assertion failure in NullEvent::setCompute with small G values#17
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When getGlobalTimeNs() truncates picoseconds to nanoseconds via integer division (now()/1000), converting back to picoseconds (×1000) can produce a value smaller than the actual eventlist().now(). This caused an unsigned underflow in NullEvent::setCompute, scheduling events in the past and triggering 'assert(when >= now())' in EventList::sourceIsPending. The bug surfaces when the LogGOPSim G parameter is small (e.g., 0.0001), because bandwidth_cost2 truncates to 0 for most message sizes, so can_simulate_until stays at the truncated current time rather than advancing into the future. Fixes: 1. null_event.cpp: Guard against underflow by clamping the relative offset to 0 when the target time is at or before now. 2. logsim-interface.cpp (htsim_simulate_until): Clamp the 'until' parameter to at least the current HTSIM time before scheduling. 3. logsim-interface.cpp (OP_SEND): Use std::ceil + std::max(1,...) for bandwidth_cost2 so it never truncates to 0, preventing send pileups that also cause extreme simulation slowdowns. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Problem
When the LogGOPSim
Gparameter is set to a small value (e.g., 0.0001), the simulation:Assertion 'when >= now()' failedinEventList::sourceIsPending()Root Cause
getGlobalTimeNs()returnseventlist().now() / 1000, integer division that truncates sub-nanosecond precision. When this truncated value flows back throughNullEvent::setCompute(ns_value)which doesns_value * 1000, the round-tripped picosecond value is smaller thaneventlist().now(), causing an unsigned underflow that schedules events in the past.Fixes
null_event.cpp: Guard against unsigned underflow by clamping the relative offset to 0 when target time ≤ nowlogsim-interface.cpp(htsim_simulate_until): Clampuntilto at least current HTSIM time before schedulinglogsim-interface.cpp(OP_SEND): Usestd::ceil+std::max(1,...)forbandwidth_cost2so it never truncates to 0