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dmrg: refuse MEASURE_* parameters with a clear error instead of SIGSEGV #101

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dmrg: refuse MEASURE_* parameters with a clear error instead of SIGSEGV #101

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31 changes: 30 additions & 1 deletion applications/dmrg/dmrg/dmrg.h
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Original file line number Diff line number Diff line change
Expand Up @@ -269,7 +269,36 @@ void DMRGTask<value_type>::dostep()
{
if (finished())
return;


// The measurement-rotation path (dmtk::System::rotate_hami) dereferences
// the result of System::operator()(op) without a null check. operator()
// legitimately returns 0 when a measurement operator's site is not yet
// covered by the current b1..b4 block layout for a given final_sweep
// iteration -- which is always the case during the first iterations for
// sites near the chain endpoints. Every input requesting MEASURE_LOCAL /
// MEASURE_AVERAGE / MEASURE_CORRELATIONS / MEASURE_STRUCTURE_FACTOR
// therefore crashes with SIGSEGV before producing any output.
//
// A correct fix needs the block operator-set bookkeeping re-derived so
// measurement operators are guaranteed present at every iteration. Until
// then, refuse the request with a clear error instead of crashing.
// (The mps_optim application, which supported the same MEASURE_* syntax,
// was removed from this repository; releases up to and including the last
// one that shipped it can be used for these measurements.)
if (!this->local_expressions.empty()
|| !this->average_expressions.empty()
|| !this->correlation_expressions.empty()
|| !this->structurefactor_expressions.empty()) {
boost::throw_exception(std::runtime_error(
"MEASURE_LOCAL / MEASURE_AVERAGE / MEASURE_CORRELATIONS / "
"MEASURE_STRUCTURE_FACTOR are not supported by the classic 'dmrg' "
"binary: the legacy DMTK measurement path dereferences a null "
"operator lookup in dmtk::System::rotate_hami and crashes. Remove "
"the MEASURE_* parameters to compute the energy/entropy only, or "
"use the 'mps_optim' application from an ALPS release that still "
"ships it to evaluate these observables."));
}

dmtk::Lattice l(num_sites(),dmtk::OBC);
hami = dmtk::Hami<value_type >(l);
site_block.resize(alps::maximum_vertex_type(graph())+1);
Expand Down