# the default option of NDSolve

How should I find out what the default value of Accuracy and Precision is in the NDSolve? I have a pde that when I asked it to solve for me the equation with a special Accuracy and precision it gave me back an error, but if I live the NDSolve with its default. It would solve it. I don't know how to find the value of accuracy and precision. another basic question which have is about the meaning of the Accuracy and precision. I know the meaning in general from high school, but the problem is that I do not know the meaning of Accuracy->15, does it calculate it for 15 decimal number or what?

• You can do Options[NDSolve] and see the default values. It says Automatic for some. Then go to each and looks at its help. For Accuracy it says AccuracyGoal->Automatic normally yields an accuracy goal equal to half the setting for WorkingPrecision and for PrecisionGoal it says ->Automatic normally yields a precision goal equal to half the setting for WorkingPrecision SO they depend on setting for WorkingPrecision Then you look at help for WorkingPrecision Oct 8, 2014 at 16:41

Following @Nasser's comment, both defaults are \$MachinePrecision/2, 7.97729 in my case.