I have a problem with exactly the same fitting code working differently on two machines, one with 32 and one with 64 bits. My settings for the fitter are:

```
ROOT::Math::MinimizerOptions::SetDefaultMinimizer("GSLMultiFit", "");
ROOT::Math::MinimizerOptions::SetDefaultPrintLevel(3);
ROOT::Math::MinimizerOptions::SetDefaultStrategy(1);
ROOT::Math::MinimizerOptions::SetDefaultTolerance(0.001);
```

although I am not sure if they all affect GSL

The problem is, that on one machines the fit goes on, on the second it decides on the first iteration that the tolarance cannot be reached:

```
Initial params 976.08654785 0.14824319097 -0.28525488592 3.581870079 1 488 2 1
Minimize using GSLNLSMinimizer undefined
new calc -3 -3 0.14839319097 -0.28525488592 2591.4641685 488 2 488.05062932
new calc -3 -3 0.14824319097 -0.28510488592 2591.4679096 488 3 488.0505913
GSLNLSMinimizer: Start iterating.........
new calc -3 -3 0.21234165025 -0.29249671767 2619.93383 488 4 488.05177028
new calc -3 -3 0.21249151291 -0.29249671767 2620.0142855 488 5 488.05175889
new calc -3 -3 0.21234165025 -0.29234671938 2619.8736349 488 6 488.05171682
----------> Iteration 0 / 100 status success
FVAL = 433.867933819512814
X Values : Distance = 976.08654785 X0 = 0.21234165025 Y0 = -0.29249
671767 Axis = 3.581870079 Scale = 1 Offset = 488 Power = 2 Lambda = 1 Convolutio
n = 1
after Gradient and Delta tests: the iteration has not converged yet
```

```
Initial params 976.08654785 0.14824319097 -0.28525488592 3.581870079 1 488 2 1
Minimize using GSLNLSMinimizer undefined
new calc -3 -3 0.14839319097 -0.28525488592 2591.4641685 488 2 488.05062932
new calc -3 -3 0.14824319097 -0.28510488592 2591.4679096 488 3 488.0505913
GSLNLSMinimizer: Start iterating.........
----------> Iteration 0 / 100 status cannot reach the specified tolerance in F
FVAL = 680.768965186504033
X Values : Distance = 976.08654785 X0 = 0.14824319097 Y0 = -0.28525488592 Axis = 3.581870079 Scale = 1 Offset = 488 Power = 2 Lambda = 1 Convolution = 1
GSLNLSMinimizer: Minimization did not converge
```

The lines starting with â€śnew calcâ€ť are printed from within the function. The function is called with exactly the same parameters on both machines (0.14839319097 -0.28525488592 and so on) and returns the same values for position -3 -3 (488.05062932 and so on) before â€śstart iteratingâ€ť. So I assume it is calculated properly on both machines. Why the decision about continuing the fit is different?