Difference between revisions of "IgnoreWarnings"

Revision as of 10:42, 20 August 2015

IgnoreWarnings(e)

Evaluates the expression, e, while suppressing any warnings that might otherwise be generated during the evaluation of e. For example,

IgnoreWarnings(Emissions[@Time = @Time + 1])

We strongly recommend that you keep Show Result Warnings checked in the Preferences Dialog, since warnings can help you find many modeling errors. But, sometimes you really do want to do something that generates a warning. For example, you may intentionally want to allow an out-of-range subscript, which returns NULL when warnings are ignored. Then you can wrap the expression inside IgnoreWarnings to suppress the warnings, while leaving Show Result Warnings checked.

Speeding calculations with IgnoreWarnings

Judicious use of IgnoreWarnings can speed up calculation where inner expressions encounter many warning conditions that do not propagate to the final result. Consider:

IF X>0 THEN Sqrt(X) ELSE Sqrt(-X)

If X is an array, this expression generates a warning condition for every non-zero element of X, since either Sqrt(X) or Sqrt(-X) requires a warning. You won't see these warnings, since none of them make it to the top level. But Analytica must do extra bookkeeping to track the warnings and decide whether it needs to display them. So, it will evaluate more quickly (especially if X large) if you embed the expression inside IgnoreWarnings, i.e.:

IgnoreWarnings(IF X>0 THEN Sqrt(X) ELSE Sqrt(-X))

This example is only for illustration -- it would be simpler and faster still to use the equivalent:

 Sqrt(Abs(X))

@@ Line 2: / Line 2: @@
 [[Category:Doc Status C]] <!-- For Lumina use, do not change -->
-= IgnoreWarnings(e) =
+== IgnoreWarnings(e) ==
-Evaluates the expression, ''e'', while suppressing any warnings that might otherwise be generated during the evaluation of ''e''.
+Evaluates the expression, ''e'', while suppressing any warnings that might otherwise be generated during the evaluation of ''e''.  For example,
+ IgnoreWarnings(Emissions[@Time = @Time + 1])
-We highly recommend that you keep the ''Show Result Warnings'' checked in the [[Preferences]] Dialog, since warnings can help you find many modeling errors.  However, sometimes you really do want to do something that generates a warning.  For example, you may intentionally want to allow an out-of-range subscript, which returns NULL when warnings are ignored.  In these cases, you can wrap the expression inside '''IgnoreWarnings''' to suppress the warnings, while leaving ''Show Result Warnings'' checked.
+We strongly recommend that you keep '''Show Result Warnings''' checked in the [[Preferences]] Dialog, since warnings can help you find many modeling errors.  But, sometimes you really do want to do something that generates a warning.  For example, you may intentionally want to allow an out-of-range subscript, which returns NULL when warnings are ignored.  Then you can wrap the expression inside '''IgnoreWarnings''' to suppress the warnings, while leaving ''Show Result Warnings'' checked.
-= Example =
- IgnoreWarnings( Emissions[@Time=@Time+1] )
+=== Speeding calculations with IgnoreWarnings ===
-= Notes =
+Judicious use of '''IgnoreWarnings''' can speed up calculation where inner expressions encounter many warning conditions that do not propagate to the final result.  Consider:
+ IF X>0 THEN Sqrt(X) ELSE Sqrt(-X)
-Judicious use of '''IgnoreWarnings''' can speed up calculation in some cases where inner expressions encounter many warning conditions, which do not propagate to the final result.  Consider:
+If X is an array, this expression generates a warning condition for every non-zero element of X, since either Sqrt(X) or Sqrt(-X) requires a warning.  You won't see these warnings, since none of them make it to the top level. But Analytica must do extra bookkeeping to track the warnings and decide whether it needs to display them. So, it will evaluate more quickly (especially if X large) if you embed the expression inside IgnoreWarnings, i.e.:
-  If x>0 then Sqrt(X) else Sqrt(-X)
+  IgnoreWarnings(IF X>0 THEN Sqrt(X) ELSE Sqrt(-X))
-This expression encounters a warning condition for every X (assuming they are all non-zero), since either Sqrt(X) or Sqrt(-X) requires a warning.  You will not see any of these warnings, since none of them make it to the top level. But Analytica must do extra bookkeeping to track the warnings and decide whether it needs to display them. So, it will evaluate more quickly (especially if x large) if you embed the expression inside IgnoreWarnings, i.e.:
+This example is only for illustration -- it would be simpler and faster still to use the equivalent:
- IgnoreWarnings(IF x>0 THEN Sqrt(X) ELSE Sqrt(-X))
-We chose this example for illustration only -- it would be simpler and faster still to use the equivalent:
    Sqrt(Abs(X))