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Guard call to inverse #40
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Use `detLU` to check that the input matrix is not singular before attempting to calculate the inverse. Closes Daniel-Diaz#38.
octopuscabbage
approved these changes
Sep 16, 2016
| @@ -543,12 +543,14 @@ transpose m = matrix (ncols m) (nrows m) $ \(i,j) -> m ! (j,i) | |||
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| -- | /O(rows*rows*rows) = O(cols*cols*cols)/. The inverse of a square matrix. | |||
| -- Uses naive Gaussian elimination formula. | |||
| inverse :: (Fractional a, Eq a) => Matrix a -> Either String (Matrix a) | |||
| inverse :: (Fractional a, Ord a) => Matrix a -> Either String (Matrix a) | |||
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Why did this change from Eq to Ord?
| inverse m | ||
| | ncols m /= nrows m | ||
| = Left | ||
| $ "Inverting non-square matrix with dimensions " | ||
| ++ show (sizeStr (ncols m) (nrows m)) | ||
| | detLU m == 0 |
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with regards to determining the determinant and performance: I think we should go with safety instead of performance in this library because if someone really wants a performant matrix library they would probably use some GPU accelerated c library.
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Use
detLUto check that the input matrix is not singular before attempting to calculate the inverse.Would close #38, though in a clumsy fashion.
Right now the
inversefunction (or rather, internalrref) has a ton of error checking. I feel like there should be two paths to calculate the inverse; a safe, guarded one that accepts it might be more expensive to run (in which case might as well use the Caley-Hamilton method) and an unsafe, express, assume-you-know-what-you're-doing, maybeanyway, patch attached
AfC