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1 | {-# OPTIONS_GHC -Wall #-} | ||
2 | |||
3 | {-# LANGUAGE QuasiQuotes #-} | ||
4 | {-# LANGUAGE TemplateHaskell #-} | ||
5 | {-# LANGUAGE MultiWayIf #-} | ||
6 | {-# LANGUAGE OverloadedStrings #-} | ||
7 | {-# LANGUAGE ScopedTypeVariables #-} | ||
8 | |||
9 | ----------------------------------------------------------------------------- | ||
10 | -- | | ||
11 | -- Module : Numeric.Sundials.CVode.ODE | ||
12 | -- Copyright : Dominic Steinitz 2018, | ||
13 | -- Novadiscovery 2018 | ||
14 | -- License : BSD | ||
15 | -- Maintainer : Dominic Steinitz | ||
16 | -- Stability : provisional | ||
17 | -- | ||
18 | -- Solution of ordinary differential equation (ODE) initial value problems. | ||
19 | -- | ||
20 | -- <https://computation.llnl.gov/projects/sundials/sundials-software> | ||
21 | -- | ||
22 | -- A simple example: | ||
23 | -- | ||
24 | -- <<diagrams/brusselator.png#diagram=brusselator&height=400&width=500>> | ||
25 | -- | ||
26 | -- @ | ||
27 | -- import Numeric.Sundials.CVode.ODE | ||
28 | -- import Numeric.LinearAlgebra | ||
29 | -- | ||
30 | -- import Plots as P | ||
31 | -- import qualified Diagrams.Prelude as D | ||
32 | -- import Diagrams.Backend.Rasterific | ||
33 | -- | ||
34 | -- brusselator :: Double -> [Double] -> [Double] | ||
35 | -- brusselator _t x = [ a - (w + 1) * u + v * u * u | ||
36 | -- , w * u - v * u * u | ||
37 | -- , (b - w) / eps - w * u | ||
38 | -- ] | ||
39 | -- where | ||
40 | -- a = 1.0 | ||
41 | -- b = 3.5 | ||
42 | -- eps = 5.0e-6 | ||
43 | -- u = x !! 0 | ||
44 | -- v = x !! 1 | ||
45 | -- w = x !! 2 | ||
46 | -- | ||
47 | -- lSaxis :: [[Double]] -> P.Axis B D.V2 Double | ||
48 | -- lSaxis xs = P.r2Axis &~ do | ||
49 | -- let ts = xs!!0 | ||
50 | -- us = xs!!1 | ||
51 | -- vs = xs!!2 | ||
52 | -- ws = xs!!3 | ||
53 | -- P.linePlot' $ zip ts us | ||
54 | -- P.linePlot' $ zip ts vs | ||
55 | -- P.linePlot' $ zip ts ws | ||
56 | -- | ||
57 | -- main = do | ||
58 | -- let res1 = odeSolve brusselator [1.2, 3.1, 3.0] (fromList [0.0, 0.1 .. 10.0]) | ||
59 | -- renderRasterific "diagrams/brusselator.png" | ||
60 | -- (D.dims2D 500.0 500.0) | ||
61 | -- (renderAxis $ lSaxis $ [0.0, 0.1 .. 10.0]:(toLists $ tr res1)) | ||
62 | -- @ | ||
63 | -- | ||
64 | -- KVAERNO_4_2_3 | ||
65 | -- | ||
66 | -- \[ | ||
67 | -- \begin{array}{c|cccc} | ||
68 | -- 0.0 & 0.0 & 0.0 & 0.0 & 0.0 \\ | ||
69 | -- 0.871733043 & 0.4358665215 & 0.4358665215 & 0.0 & 0.0 \\ | ||
70 | -- 1.0 & 0.490563388419108 & 7.3570090080892e-2 & 0.4358665215 & 0.0 \\ | ||
71 | -- 1.0 & 0.308809969973036 & 1.490563388254106 & -1.235239879727145 & 0.4358665215 \\ | ||
72 | -- \hline | ||
73 | -- & 0.308809969973036 & 1.490563388254106 & -1.235239879727145 & 0.4358665215 \\ | ||
74 | -- & 0.490563388419108 & 7.3570090080892e-2 & 0.4358665215 & 0.0 \\ | ||
75 | -- \end{array} | ||
76 | -- \] | ||
77 | -- | ||
78 | -- SDIRK_2_1_2 | ||
79 | -- | ||
80 | -- \[ | ||
81 | -- \begin{array}{c|cc} | ||
82 | -- 1.0 & 1.0 & 0.0 \\ | ||
83 | -- 0.0 & -1.0 & 1.0 \\ | ||
84 | -- \hline | ||
85 | -- & 0.5 & 0.5 \\ | ||
86 | -- & 1.0 & 0.0 \\ | ||
87 | -- \end{array} | ||
88 | -- \] | ||
89 | -- | ||
90 | -- SDIRK_5_3_4 | ||
91 | -- | ||
92 | -- \[ | ||
93 | -- \begin{array}{c|ccccc} | ||
94 | -- 0.25 & 0.25 & 0.0 & 0.0 & 0.0 & 0.0 \\ | ||
95 | -- 0.75 & 0.5 & 0.25 & 0.0 & 0.0 & 0.0 \\ | ||
96 | -- 0.55 & 0.34 & -4.0e-2 & 0.25 & 0.0 & 0.0 \\ | ||
97 | -- 0.5 & 0.2727941176470588 & -5.036764705882353e-2 & 2.7573529411764705e-2 & 0.25 & 0.0 \\ | ||
98 | -- 1.0 & 1.0416666666666667 & -1.0208333333333333 & 7.8125 & -7.083333333333333 & 0.25 \\ | ||
99 | -- \hline | ||
100 | -- & 1.0416666666666667 & -1.0208333333333333 & 7.8125 & -7.083333333333333 & 0.25 \\ | ||
101 | -- & 1.2291666666666667 & -0.17708333333333334 & 7.03125 & -7.083333333333333 & 0.0 \\ | ||
102 | -- \end{array} | ||
103 | -- \] | ||
104 | ----------------------------------------------------------------------------- | ||
105 | module Numeric.Sundials.CVode.ODE ( odeSolve | ||
106 | , odeSolveV | ||
107 | , odeSolveVWith | ||
108 | , odeSolveVWith' | ||
109 | , ODEMethod(..) | ||
110 | , StepControl(..) | ||
111 | , Jacobian | ||
112 | , SundialsDiagnostics(..) | ||
113 | ) where | ||
114 | |||
115 | import qualified Language.C.Inline as C | ||
116 | import qualified Language.C.Inline.Unsafe as CU | ||
117 | |||
118 | import Data.Monoid ((<>)) | ||
119 | import Data.Maybe (isJust) | ||
120 | |||
121 | import Foreign.C.Types | ||
122 | import Foreign.Ptr (Ptr) | ||
123 | import Foreign.ForeignPtr (newForeignPtr_) | ||
124 | import Foreign.Storable (Storable) | ||
125 | |||
126 | import qualified Data.Vector.Storable as V | ||
127 | import qualified Data.Vector.Storable.Mutable as VM | ||
128 | |||
129 | import Data.Coerce (coerce) | ||
130 | import System.IO.Unsafe (unsafePerformIO) | ||
131 | |||
132 | import Numeric.LinearAlgebra.Devel (createVector) | ||
133 | |||
134 | import Numeric.LinearAlgebra.HMatrix (Vector, Matrix, toList, (><), | ||
135 | subMatrix, rows, cols, toLists, | ||
136 | size, subVector) | ||
137 | |||
138 | import qualified Types as T | ||
139 | import Arkode (cV_ADAMS, cV_BDF) | ||
140 | import qualified Arkode as B | ||
141 | |||
142 | |||
143 | C.context (C.baseCtx <> C.vecCtx <> C.funCtx <> T.sunCtx) | ||
144 | |||
145 | C.include "<stdlib.h>" | ||
146 | C.include "<stdio.h>" | ||
147 | C.include "<math.h>" | ||
148 | C.include "<cvode/cvode.h>" -- prototypes for CVODE fcts., consts. | ||
149 | C.include "<nvector/nvector_serial.h>" -- serial N_Vector types, fcts., macros | ||
150 | C.include "<sunmatrix/sunmatrix_dense.h>" -- access to dense SUNMatrix | ||
151 | C.include "<sunlinsol/sunlinsol_dense.h>" -- access to dense SUNLinearSolver | ||
152 | C.include "<cvode/cvode_direct.h>" -- access to CVDls interface | ||
153 | C.include "<sundials/sundials_types.h>" -- definition of type realtype | ||
154 | C.include "<sundials/sundials_math.h>" | ||
155 | C.include "../../../helpers.h" | ||
156 | C.include "Arkode_hsc.h" | ||
157 | |||
158 | |||
159 | getDataFromContents :: Int -> Ptr T.SunVector -> IO (V.Vector CDouble) | ||
160 | getDataFromContents len ptr = do | ||
161 | qtr <- B.getContentPtr ptr | ||
162 | rtr <- B.getData qtr | ||
163 | vectorFromC len rtr | ||
164 | |||
165 | -- FIXME: Potentially an instance of Storable | ||
166 | _getMatrixDataFromContents :: Ptr T.SunMatrix -> IO T.SunMatrix | ||
167 | _getMatrixDataFromContents ptr = do | ||
168 | qtr <- B.getContentMatrixPtr ptr | ||
169 | rs <- B.getNRows qtr | ||
170 | cs <- B.getNCols qtr | ||
171 | rtr <- B.getMatrixData qtr | ||
172 | vs <- vectorFromC (fromIntegral $ rs * cs) rtr | ||
173 | return $ T.SunMatrix { T.rows = rs, T.cols = cs, T.vals = vs } | ||
174 | |||
175 | putMatrixDataFromContents :: T.SunMatrix -> Ptr T.SunMatrix -> IO () | ||
176 | putMatrixDataFromContents mat ptr = do | ||
177 | let rs = T.rows mat | ||
178 | cs = T.cols mat | ||
179 | vs = T.vals mat | ||
180 | qtr <- B.getContentMatrixPtr ptr | ||
181 | B.putNRows rs qtr | ||
182 | B.putNCols cs qtr | ||
183 | rtr <- B.getMatrixData qtr | ||
184 | vectorToC vs (fromIntegral $ rs * cs) rtr | ||
185 | -- FIXME: END | ||
186 | |||
187 | putDataInContents :: Storable a => V.Vector a -> Int -> Ptr b -> IO () | ||
188 | putDataInContents vec len ptr = do | ||
189 | qtr <- B.getContentPtr ptr | ||
190 | rtr <- B.getData qtr | ||
191 | vectorToC vec len rtr | ||
192 | |||
193 | -- Utils | ||
194 | |||
195 | vectorFromC :: Storable a => Int -> Ptr a -> IO (V.Vector a) | ||
196 | vectorFromC len ptr = do | ||
197 | ptr' <- newForeignPtr_ ptr | ||
198 | V.freeze $ VM.unsafeFromForeignPtr0 ptr' len | ||
199 | |||
200 | vectorToC :: Storable a => V.Vector a -> Int -> Ptr a -> IO () | ||
201 | vectorToC vec len ptr = do | ||
202 | ptr' <- newForeignPtr_ ptr | ||
203 | V.copy (VM.unsafeFromForeignPtr0 ptr' len) vec | ||
204 | |||
205 | data SundialsDiagnostics = SundialsDiagnostics { | ||
206 | aRKodeGetNumSteps :: Int | ||
207 | , aRKodeGetNumStepAttempts :: Int | ||
208 | , aRKodeGetNumRhsEvals_fe :: Int | ||
209 | , aRKodeGetNumRhsEvals_fi :: Int | ||
210 | , aRKodeGetNumLinSolvSetups :: Int | ||
211 | , aRKodeGetNumErrTestFails :: Int | ||
212 | , aRKodeGetNumNonlinSolvIters :: Int | ||
213 | , aRKodeGetNumNonlinSolvConvFails :: Int | ||
214 | , aRKDlsGetNumJacEvals :: Int | ||
215 | , aRKDlsGetNumRhsEvals :: Int | ||
216 | } deriving Show | ||
217 | |||
218 | type Jacobian = Double -> Vector Double -> Matrix Double | ||
219 | |||
220 | -- | Stepping functions | ||
221 | data ODEMethod = ADAMS | ||
222 | | BDF | ||
223 | |||
224 | getMethod :: ODEMethod -> Int | ||
225 | getMethod (ADAMS) = cV_ADAMS | ||
226 | getMethod (BDF) = cV_BDF | ||
227 | |||
228 | getJacobian :: ODEMethod -> Maybe Jacobian | ||
229 | getJacobian _ = Nothing | ||
230 | |||
231 | -- | A version of 'odeSolveVWith' with reasonable default step control. | ||
232 | odeSolveV | ||
233 | :: ODEMethod | ||
234 | -> Maybe Double -- ^ initial step size - by default, ARKode | ||
235 | -- estimates the initial step size to be the | ||
236 | -- solution \(h\) of the equation | ||
237 | -- \(\|\frac{h^2\ddot{y}}{2}\| = 1\), where | ||
238 | -- \(\ddot{y}\) is an estimated value of the | ||
239 | -- second derivative of the solution at \(t_0\) | ||
240 | -> Double -- ^ absolute tolerance for the state vector | ||
241 | -> Double -- ^ relative tolerance for the state vector | ||
242 | -> (Double -> Vector Double -> Vector Double) -- ^ The RHS of the system \(\dot{y} = f(t,y)\) | ||
243 | -> Vector Double -- ^ initial conditions | ||
244 | -> Vector Double -- ^ desired solution times | ||
245 | -> Matrix Double -- ^ solution | ||
246 | odeSolveV meth hi epsAbs epsRel f y0 ts = | ||
247 | case odeSolveVWith meth (X epsAbs epsRel) hi g y0 ts of | ||
248 | Left c -> error $ show c -- FIXME | ||
249 | -- FIXME: Can we do better than using lists? | ||
250 | Right (v, d) -> (nR >< nC) (V.toList v) | ||
251 | where | ||
252 | us = toList ts | ||
253 | nR = length us | ||
254 | nC = size y0 | ||
255 | g t x0 = coerce $ f t x0 | ||
256 | |||
257 | -- | A version of 'odeSolveV' with reasonable default parameters and | ||
258 | -- system of equations defined using lists. FIXME: we should say | ||
259 | -- something about the fact we could use the Jacobian but don't for | ||
260 | -- compatibility with hmatrix-gsl. | ||
261 | odeSolve :: (Double -> [Double] -> [Double]) -- ^ The RHS of the system \(\dot{y} = f(t,y)\) | ||
262 | -> [Double] -- ^ initial conditions | ||
263 | -> Vector Double -- ^ desired solution times | ||
264 | -> Matrix Double -- ^ solution | ||
265 | odeSolve f y0 ts = | ||
266 | -- FIXME: These tolerances are different from the ones in GSL | ||
267 | case odeSolveVWith BDF (XX' 1.0e-6 1.0e-10 1 1) Nothing g (V.fromList y0) (V.fromList $ toList ts) of | ||
268 | Left c -> error $ show c -- FIXME | ||
269 | Right (v, d) -> (nR >< nC) (V.toList v) | ||
270 | where | ||
271 | us = toList ts | ||
272 | nR = length us | ||
273 | nC = length y0 | ||
274 | g t x0 = V.fromList $ f t (V.toList x0) | ||
275 | |||
276 | odeSolveVWith' :: | ||
277 | ODEMethod | ||
278 | -> StepControl | ||
279 | -> Maybe Double -- ^ initial step size - by default, ARKode | ||
280 | -- estimates the initial step size to be the | ||
281 | -- solution \(h\) of the equation | ||
282 | -- \(\|\frac{h^2\ddot{y}}{2}\| = 1\), where | ||
283 | -- \(\ddot{y}\) is an estimated value of the second | ||
284 | -- derivative of the solution at \(t_0\) | ||
285 | -> (Double -> V.Vector Double -> V.Vector Double) -- ^ The RHS of the system \(\dot{y} = f(t,y)\) | ||
286 | -> V.Vector Double -- ^ Initial conditions | ||
287 | -> V.Vector Double -- ^ Desired solution times | ||
288 | -> Matrix Double -- ^ Error code or solution | ||
289 | odeSolveVWith' method control initStepSize f y0 tt = | ||
290 | case odeSolveVWith method control initStepSize f y0 tt of | ||
291 | Left c -> error $ show c -- FIXME | ||
292 | Right (v, _d) -> (nR >< nC) (V.toList v) | ||
293 | where | ||
294 | nR = V.length tt | ||
295 | nC = V.length y0 | ||
296 | |||
297 | odeSolveVWith :: | ||
298 | ODEMethod | ||
299 | -> StepControl | ||
300 | -> Maybe Double -- ^ initial step size - by default, ARKode | ||
301 | -- estimates the initial step size to be the | ||
302 | -- solution \(h\) of the equation | ||
303 | -- \(\|\frac{h^2\ddot{y}}{2}\| = 1\), where | ||
304 | -- \(\ddot{y}\) is an estimated value of the second | ||
305 | -- derivative of the solution at \(t_0\) | ||
306 | -> (Double -> V.Vector Double -> V.Vector Double) -- ^ The RHS of the system \(\dot{y} = f(t,y)\) | ||
307 | -> V.Vector Double -- ^ Initial conditions | ||
308 | -> V.Vector Double -- ^ Desired solution times | ||
309 | -> Either Int ((V.Vector Double), SundialsDiagnostics) -- ^ Error code or solution | ||
310 | odeSolveVWith method control initStepSize f y0 tt = | ||
311 | case solveOdeC (fromIntegral $ getMethod method) (coerce initStepSize) jacH (scise control) | ||
312 | (coerce f) (coerce y0) (coerce tt) of | ||
313 | Left c -> Left $ fromIntegral c | ||
314 | Right (v, d) -> Right (coerce v, d) | ||
315 | where | ||
316 | l = size y0 | ||
317 | scise (X absTol relTol) = coerce (V.replicate l absTol, relTol) | ||
318 | scise (X' absTol relTol) = coerce (V.replicate l absTol, relTol) | ||
319 | scise (XX' absTol relTol yScale _yDotScale) = coerce (V.replicate l absTol, yScale * relTol) | ||
320 | -- FIXME; Should we check that the length of ss is correct? | ||
321 | scise (ScXX' absTol relTol yScale _yDotScale ss) = coerce (V.map (* absTol) ss, yScale * relTol) | ||
322 | jacH = fmap (\g t v -> matrixToSunMatrix $ g (coerce t) (coerce v)) $ | ||
323 | getJacobian method | ||
324 | matrixToSunMatrix m = T.SunMatrix { T.rows = nr, T.cols = nc, T.vals = vs } | ||
325 | where | ||
326 | nr = fromIntegral $ rows m | ||
327 | nc = fromIntegral $ cols m | ||
328 | -- FIXME: efficiency | ||
329 | vs = V.fromList $ map coerce $ concat $ toLists m | ||
330 | |||
331 | solveOdeC :: | ||
332 | CInt -> | ||
333 | Maybe CDouble -> | ||
334 | (Maybe (CDouble -> V.Vector CDouble -> T.SunMatrix)) -> | ||
335 | (V.Vector CDouble, CDouble) -> | ||
336 | (CDouble -> V.Vector CDouble -> V.Vector CDouble) -- ^ The RHS of the system \(\dot{y} = f(t,y)\) | ||
337 | -> V.Vector CDouble -- ^ Initial conditions | ||
338 | -> V.Vector CDouble -- ^ Desired solution times | ||
339 | -> Either CInt ((V.Vector CDouble), SundialsDiagnostics) -- ^ Error code or solution | ||
340 | solveOdeC method initStepSize jacH (absTols, relTol) fun f0 ts = unsafePerformIO $ do | ||
341 | |||
342 | let isInitStepSize :: CInt | ||
343 | isInitStepSize = fromIntegral $ fromEnum $ isJust initStepSize | ||
344 | ss :: CDouble | ||
345 | ss = case initStepSize of | ||
346 | -- It would be better to put an error message here but | ||
347 | -- inline-c seems to evaluate this even if it is never | ||
348 | -- used :( | ||
349 | Nothing -> 0.0 | ||
350 | Just x -> x | ||
351 | let dim = V.length f0 | ||
352 | nEq :: CLong | ||
353 | nEq = fromIntegral dim | ||
354 | nTs :: CInt | ||
355 | nTs = fromIntegral $ V.length ts | ||
356 | -- FIXME: fMut is not actually mutatated | ||
357 | fMut <- V.thaw f0 | ||
358 | tMut <- V.thaw ts | ||
359 | -- FIXME: I believe this gets taken from the ghc heap and so should | ||
360 | -- be subject to garbage collection. | ||
361 | -- quasiMatrixRes <- createVector ((fromIntegral dim) * (fromIntegral nTs)) | ||
362 | -- qMatMut <- V.thaw quasiMatrixRes | ||
363 | diagnostics :: V.Vector CLong <- createVector 10 -- FIXME | ||
364 | diagMut <- V.thaw diagnostics | ||
365 | -- We need the types that sundials expects. These are tied together | ||
366 | -- in 'Types'. FIXME: The Haskell type is currently empty! | ||
367 | let funIO :: CDouble -> Ptr T.SunVector -> Ptr T.SunVector -> Ptr () -> IO CInt | ||
368 | funIO x y f _ptr = do | ||
369 | -- Convert the pointer we get from C (y) to a vector, and then | ||
370 | -- apply the user-supplied function. | ||
371 | fImm <- fun x <$> getDataFromContents dim y | ||
372 | -- Fill in the provided pointer with the resulting vector. | ||
373 | putDataInContents fImm dim f | ||
374 | -- FIXME: I don't understand what this comment means | ||
375 | -- Unsafe since the function will be called many times. | ||
376 | [CU.exp| int{ 0 } |] | ||
377 | let isJac :: CInt | ||
378 | isJac = fromIntegral $ fromEnum $ isJust jacH | ||
379 | jacIO :: CDouble -> Ptr T.SunVector -> Ptr T.SunVector -> Ptr T.SunMatrix -> | ||
380 | Ptr () -> Ptr T.SunVector -> Ptr T.SunVector -> Ptr T.SunVector -> | ||
381 | IO CInt | ||
382 | jacIO t y _fy jacS _ptr _tmp1 _tmp2 _tmp3 = do | ||
383 | case jacH of | ||
384 | Nothing -> error "Numeric.Sundials.ARKode.ODE: Jacobian not defined" | ||
385 | Just jacI -> do j <- jacI t <$> getDataFromContents dim y | ||
386 | putMatrixDataFromContents j jacS | ||
387 | -- FIXME: I don't understand what this comment means | ||
388 | -- Unsafe since the function will be called many times. | ||
389 | [CU.exp| int{ 0 } |] | ||
390 | |||
391 | res <- [C.block| int { | ||
392 | /* general problem variables */ | ||
393 | |||
394 | int flag; /* reusable error-checking flag */ | ||
395 | int i, j; /* reusable loop indices */ | ||
396 | N_Vector y = NULL; /* empty vector for storing solution */ | ||
397 | void *cvode_mem = NULL; /* empty CVODE memory structure */ | ||
398 | |||
399 | /* general problem parameters */ | ||
400 | |||
401 | realtype T0 = RCONST(($vec-ptr:(double *ts))[0]); /* initial time */ | ||
402 | sunindextype NEQ = $(sunindextype nEq); /* number of dependent vars. */ | ||
403 | |||
404 | /* Initialize data structures */ | ||
405 | |||
406 | y = N_VNew_Serial(NEQ); /* Create serial vector for solution */ | ||
407 | if (check_flag((void *)y, "N_VNew_Serial", 0)) return 1; | ||
408 | /* Specify initial condition */ | ||
409 | for (i = 0; i < NEQ; i++) { | ||
410 | NV_Ith_S(y,i) = ($vec-ptr:(double *f0))[i]; | ||
411 | }; | ||
412 | |||
413 | cvode_mem = CVodeCreate(CV_BDF, CV_NEWTON); | ||
414 | if (check_flag((void *)cvode_mem, "CVodeCreate", 0)) return(1); | ||
415 | |||
416 | /* Call CVodeInit to initialize the integrator memory and specify the | ||
417 | * user's right hand side function in y'=f(t,y), the inital time T0, and | ||
418 | * the initial dependent variable vector y. */ | ||
419 | flag = CVodeInit(cvode_mem, $fun:(int (* funIO) (double t, SunVector y[], SunVector dydt[], void * params)), T0, y); | ||
420 | if (check_flag(&flag, "CVodeInit", 1)) return(1); | ||
421 | |||
422 | /* Clean up and return */ | ||
423 | |||
424 | N_VDestroy(y); /* Free y vector */ | ||
425 | CVodeFree(&cvode_mem); /* Free integrator memory */ | ||
426 | |||
427 | return flag; | ||
428 | } |] | ||
429 | if res == 0 | ||
430 | then do | ||
431 | return $ Left res | ||
432 | else do | ||
433 | return $ Left res | ||
434 | |||
435 | -- | Adaptive step-size control | ||
436 | -- functions. | ||
437 | -- | ||
438 | -- [GSL](https://www.gnu.org/software/gsl/doc/html/ode-initval.html#adaptive-step-size-control) | ||
439 | -- allows the user to control the step size adjustment using | ||
440 | -- \(D_i = \epsilon^{abs}s_i + \epsilon^{rel}(a_{y} |y_i| + a_{dy/dt} h |\dot{y}_i|)\) where | ||
441 | -- \(\epsilon^{abs}\) is the required absolute error, \(\epsilon^{rel}\) | ||
442 | -- is the required relative error, \(s_i\) is a vector of scaling | ||
443 | -- factors, \(a_{y}\) is a scaling factor for the solution \(y\) and | ||
444 | -- \(a_{dydt}\) is a scaling factor for the derivative of the solution \(dy/dt\). | ||
445 | -- | ||
446 | -- [ARKode](https://computation.llnl.gov/projects/sundials/arkode) | ||
447 | -- allows the user to control the step size adjustment using | ||
448 | -- \(\eta^{rel}|y_i| + \eta^{abs}_i\). For compatibility with | ||
449 | -- [hmatrix-gsl](https://hackage.haskell.org/package/hmatrix-gsl), | ||
450 | -- tolerances for \(y\) and \(\dot{y}\) can be specified but the latter have no | ||
451 | -- effect. | ||
452 | data StepControl = X Double Double -- ^ absolute and relative tolerance for \(y\); in GSL terms, \(a_{y} = 1\) and \(a_{dy/dt} = 0\); in ARKode terms, the \(\eta^{abs}_i\) are identical | ||
453 | | X' Double Double -- ^ absolute and relative tolerance for \(\dot{y}\); in GSL terms, \(a_{y} = 0\) and \(a_{dy/dt} = 1\); in ARKode terms, the latter is treated as the relative tolerance for \(y\) so this is the same as specifying 'X' which may be entirely incorrect for the given problem | ||
454 | | XX' Double Double Double Double -- ^ include both via relative tolerance | ||
455 | -- scaling factors \(a_y\), \(a_{{dy}/{dt}}\); in ARKode terms, the latter is ignored and \(\eta^{rel} = a_{y}\epsilon^{rel}\) | ||
456 | | ScXX' Double Double Double Double (Vector Double) -- ^ scale absolute tolerance of \(y_i\); in ARKode terms, \(a_{{dy}/{dt}}\) is ignored, \(\eta^{abs}_i = s_i \epsilon^{abs}\) and \(\eta^{rel} = a_{y}\epsilon^{rel}\) | ||