05-08-2026, 08:31 PM
For your information, I had a look at this issue again while preparing a new release with some other small improvements. And, I decided now to implement a small correction for the LUMPINV reporting when ILED is defined but with ILED<1, because your issue disclosed that the reporting for such small ILEDs was not consistent in either case (with or without MID_YEAR). Some elaboration in more detail is given below.
I remain with my position that under MID_YEAR the LUMPINV values for Cases I.2.a/b should in fact be reported differently than without MID_YEAR. This is a direct consequence of the difference in the assumed timing of the payments with and without MID_YEAR, which results in different amounts of interest during construction. These cases are both correctly accounted in the objective function, but the LUMPINV reporting for Cases I.2.a/b has thus far been kept according to the original design, regardless of MID_YEAR, because MID_YEAR basically does not affect these cases in the objective function, and to maintain backwards compatibility.
However, your issue disclosed that currently there is a clear inconsistency of the reported values when ILED<1, which is due to the generalization of the IDC calculation. Originally, only integral ILED values (1,2,3,...) were supported by the design, which was a notable limitation, and it effectively prevented using any ILED<1 for Cases I.2.a/b. Later, the ILED handling was generalized, based on a simple geometric series formula, to support any fractional values as well, and then also using ILED=0 was allowed for Cases I.2.a/b, when using OBLONG (or some alternative objective formulation). The resulting generalization was fully consistent with the original design for any integral values of ILED, but it results in a half-year’s IDC even with ILED=0, which caused the confusion with your issue. While in the objective function that half-year’s IDC accounting is indeed also fully consistent with mid-year discounting, I strongly think it should not be reported as IDC, because there is no meaningful interpretation of a zero ILED leading to such an interest. Instead, the IDC should only be interpreted as the time-shift related to mid-year discounting, and therefore it should be eliminated from the LUMPINV values. This is the correction I have now implemented, and it affects only the ILED<1 cases (which were not supported in the original design of TIMES). So, for now the reporting still otherwise remains unchanged between MID_YEAR = YES/NO, which I understood being your preference.
I hope you can agree that this small correction is justified, but if you have any reservations, please let me know.
I remain with my position that under MID_YEAR the LUMPINV values for Cases I.2.a/b should in fact be reported differently than without MID_YEAR. This is a direct consequence of the difference in the assumed timing of the payments with and without MID_YEAR, which results in different amounts of interest during construction. These cases are both correctly accounted in the objective function, but the LUMPINV reporting for Cases I.2.a/b has thus far been kept according to the original design, regardless of MID_YEAR, because MID_YEAR basically does not affect these cases in the objective function, and to maintain backwards compatibility.
However, your issue disclosed that currently there is a clear inconsistency of the reported values when ILED<1, which is due to the generalization of the IDC calculation. Originally, only integral ILED values (1,2,3,...) were supported by the design, which was a notable limitation, and it effectively prevented using any ILED<1 for Cases I.2.a/b. Later, the ILED handling was generalized, based on a simple geometric series formula, to support any fractional values as well, and then also using ILED=0 was allowed for Cases I.2.a/b, when using OBLONG (or some alternative objective formulation). The resulting generalization was fully consistent with the original design for any integral values of ILED, but it results in a half-year’s IDC even with ILED=0, which caused the confusion with your issue. While in the objective function that half-year’s IDC accounting is indeed also fully consistent with mid-year discounting, I strongly think it should not be reported as IDC, because there is no meaningful interpretation of a zero ILED leading to such an interest. Instead, the IDC should only be interpreted as the time-shift related to mid-year discounting, and therefore it should be eliminated from the LUMPINV values. This is the correction I have now implemented, and it affects only the ILED<1 cases (which were not supported in the original design of TIMES). So, for now the reporting still otherwise remains unchanged between MID_YEAR = YES/NO, which I understood being your preference.
I hope you can agree that this small correction is justified, but if you have any reservations, please let me know.