Function assertMatrExpIsNonDiverging

quest/src/core/validation.cpp:2485–2507

// type T can be DiagMatr, FullStateDiagMatr
template <class T> 
void assertMatrExpIsNonDiverging(T matr, qcomp exponent, const char* caller) {

    validate_matrixFields(matr, caller);
    validate_matrixIsSynced(matr, caller);

    // avoid exepensive and epsilon-dependent validation below (do not overwrite matr.isApproxNonZero)
    if (isNumericalValidationDisabled())
        return;

    // divergences are only validated when the imaginary component is strictly 
    // zero, otherwise alternate complex exponentiation is sometimes performed
    // with a more complicated numerical stability
    if (std::imag(exponent) != 0)
        return;

    // when the real exponent is STRICTLY less than zero, it is required that every
    // matrix element's magnitude is APPROX non-zero, to avoid 1/0 divergences. 
    // We do this independent of the size of exponent, even despite that exponents
    // really close to 0 (from below) can "counteract" the blowing up, because
    // precision is too poor near epsilon for this to be implicitly relied upon.
    if (std::real(exponent) < 0)
        assertThat(util_isApproxNonZero(matr, global_validationEpsilon), report::DIAG_MATR_APPROX_ZERO_WHILE_EXPONENT_REAL_AND_NEGATIVE, caller);
}
void validate_matrixExpIsNonDiverging(DiagMatr          m, qcomp p, const char* caller) { assertMatrExpIsNonDiverging(m, p, caller); }
void validate_matrixExpIsNonDiverging(FullStateDiagMatr m, qcomp p, const char* caller) { assertMatrExpIsNonDiverging(m, p, caller); }