Search found 8 matches

by mielke
5 years ago
Forum: Modeling
Topic: Decrease calculation time through already plausible starting point
Replies: 3
Views: 3076

Re: Decrease calculation time through already plausible starting point

Hey Renger Thanks for your reply! However, I'm having some trouble understanding where the additional value of the savepoint is, as this just stores the resulting variables in an output .gdx file? At the end of every solve, the results are currently already stored into the file 'output.gdx'. Would i...
by mielke
5 years ago
Forum: Modeling
Topic: Decrease calculation time through already plausible starting point
Replies: 3
Views: 3076

Decrease calculation time through already plausible starting point

Dear all In solving a fairly simple linear model with cplex, with high time and space resolution, the running of simulations appears to become a very time-consuming operation. Is it possible to reduce calculation time by using the solution of your previous simulation as a starting point for the new ...
by mielke
5 years ago
Forum: Solvers
Topic: Model solving frozen upon 'Scaled dual infeas'
Replies: 0
Views: 2401

Model solving frozen upon 'Scaled dual infeas'

Dear all I have a very CPU intensive and time-consuming linear model running simulations day and night, taking up to three days to solve using cplex. Now, just today, I followed the logging process of a simulation, and after 188041 seconds, it said 'Removing perturbation', followed by 'Scaled dual i...
by mielke
6 years ago
Forum: Modeling
Topic: Low CPU utilization
Replies: 4
Views: 4329

Re: Low CPU utilization

Hey Fred Thanks a lot for your quick and accurate response, I tested the threads option on my personal computer and CPU utilization increased from 30% to 100%. However, unfortunately, it did not speed up the solving (tested it with a smaller set of data). In attachment, you find the investment model...
by mielke
6 years ago
Forum: Modeling
Topic: Low CPU utilization
Replies: 4
Views: 4329

Re: Low CPU utilization

Maybe some additional info: he's generating the MIP model right now (see image attached). Does it make sense that this takes up so much time?
by mielke
6 years ago
Forum: Modeling
Topic: Low CPU utilization
Replies: 4
Views: 4329

Low CPU utilization

Dear all I'm currently solving a, relatively simple, linear model with the cplex solver, but for a huge amount of data. This makes for a very slow and time-consuming solving of the model. Now, when I enter the task manager (multiple times during the process, so it's not a one time problem), I observ...
by mielke
6 years ago
Forum: Modeling
Topic: Include 'either-or' constraint in linear model
Replies: 2
Views: 2833

Re: Include 'either-or' constraint in linear model

Hey Thanks for your quick reply! This certainly would be a possibility. However, as I do not really want to constrain power capacity, I would have to set PC_stor_new.up to be a very large number. This, together with the use of a binary variable z, would significantly increase calculation time as wel...
by mielke
6 years ago
Forum: Modeling
Topic: Include 'either-or' constraint in linear model
Replies: 2
Views: 2833

Include 'either-or' constraint in linear model

Hey guys I'm new to GAMS (which seems to be a common introduction of a problem, here), and I'm developing a cost minimisation model for adding capacity to the electricity system and the generation dispatch of the different technologies. Apart from conventional and renewable generation technologies, ...