Herbie automatically transforms floating point expressions into more accurate forms. This page troubleshoots common Herbie errors, warnings, and known issues.
Herbie error messages refer to this second for additional information and debugging tips.
This error means you mis-formatted Herbie's input. Common errors
include misspelled function names and parenthesized expressions
that should not be parenthesized. For example, in
(- (exp (x)) 1), the expression
x is a
variable so shouldn't be parenthesized.
(- (exp x) 1)
would be the correct way to write that expression.
The input format documentation has more
details on Herbie's syntax.
This error occurs when Herbie is unable to find enough valid
points. For example, the expression
(acos (+ 1000 x))
is invalid unless
(<= -1001 x -999), a rather narrow
range. The simplest fix is to increase
Specifying the range of valid points as
a precondition can also help.
This error indicates that your input has no valid inputs, usually
due to an overly restriction precondition. For example, the
(< 3 x 2) excludes all inputs. The
solution is to fix the precondition or input program.
Herbie warnings refer to this section for explanations and common actions to take.
Sometimes, an input to your expression produces an output so large
that it's best represented by a floating-point infinity. For
(exp 1000) is over 10434, so it's
much larger than the largest floating-point value. Herbie raises
this warning when too many inputs (more than 20% of them) are this
large, because that usually indicates you should set a more
Herbie raises this warning when some inputs require more than
10,000 bits to compute an exact ground truth. For example, to
(/ (exp x) (exp x)) for very
x, absurdly large numbers would be required.
Herbie discards such inputs and raises this warning. If you see
this warning, you should add a restrictive precondition, such
:pre (< -100 x 100), to prevent large inputs.
Herbie will raise this warning when it needs more than 10,000 bits to produce a string representation for a given value. This is likely the result of a bug in a third-party plugin.
Herbie uses a set of algebraic rewrite rules in order to simplify expressions, but these rules can sometimes lead to a contradiction. Herbie will automatically compensate for this, and in most cases nothing needs to be done. However, Herbie may have failed to simplify the output.
The input FPCore contains a variable that is not used in the body expression.
The input expression contains a variable that is similar in name to named constants, e.g. e instead of E.
Bugs that cannot be directly fixed are documented in this section.
When using Chrome to view web pages on your local machine, Herbie
reports cannot draw the arrow chart due to security restrictions.
--allow-file-access-from-files to fix