1. Introduction  
2. Data  
2.1. Data preparation  
2.2. Parameter space of input labels  
2.3. Observed set  
3. Network architecture and training  
3.1. Network architecture  
3.2. Network training  
4. Training results  
4.1. Estimation of internal uncertainties  
4.2. Learning from spectral features  
5. Validation of results  
5.1. Benchmark stars  
5.2. Comparison to asteroseismic surface gravities  
5.3. Globular clusters  
5.4. Thin- and thick disk populations  
6. Caveats  
7. Conclusions