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module PCHFE_95_m |
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implicit none |
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contains |
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SUBROUTINE PCHFE_95(X, F, D, SKIP, XE, FE, IERR) |
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! PURPOSE Evaluate a piecewise cubic Hermite function at an array of |
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! points. May be used by itself for Hermite interpolation, |
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! or as an evaluator for PCHIM or PCHIC. |
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! CATEGORY E3 |
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! KEYWORDS CUBIC HERMITE EVALUATION, HERMITE INTERPOLATION, PCHIP, |
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! PIECEWISE CUBIC EVALUATION |
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! PCHFE: Piecewise Cubic Hermite Function Evaluator |
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! Evaluates the cubic Hermite function defined by X, F, D at |
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! the points XE. |
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use assert_eq_m, only: assert_eq |
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REAL, intent(in):: X(:) ! real array of independent variable values |
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! The elements of X must be strictly increasing. |
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REAL, intent(in):: F(:) ! real array of function values |
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! F(I) is the value corresponding to X(I). |
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REAL, intent(in):: D(:) ! real array of derivative values |
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! D(I) is the value corresponding to X(I). |
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LOGICAL, intent(inout):: SKIP |
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! request to skip checks for validity of "x" |
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! If "skip" is false then "pchfe" will check that size(x) >= 2 and |
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! "x" is in strictly ascending order. |
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! Setting "skip" to true will save time in case these checks have |
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! already been performed (say, in "PCHIM" or "PCHIC"). |
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! "SKIP" will be set to TRUE on normal return. |
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real, intent(in):: XE(:) ! points at which the function is to be evaluated |
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! NOTES: |
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! 1. The evaluation will be most efficient if the elements of XE |
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! are increasing relative to X. |
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! That is, XE(J) .GE. X(I) |
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! implies XE(K) .GE. X(I), all K.GE.J |
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! 2. If any of the XE are outside the interval [X(1),X(N)], values |
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! are extrapolated from the nearest extreme cubic, and a warning |
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! error is returned. |
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real, intent(out):: FE(:) ! values of the cubic Hermite function |
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! defined by X, F, D at the points XE |
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integer, intent(out):: IERR ! error flag |
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! Normal return: |
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! IERR = 0 no error |
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! Warning error: |
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! IERR > 0 means that extrapolation was performed at IERR points |
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! "Recoverable" errors: |
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! IERR = -1 if N < 2 |
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! IERR = -3 if the X-array is not strictly increasing |
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! IERR = -4 if NE < 1 |
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! NOTE: The above errors are checked in the order listed, and |
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! following arguments have **NOT** been validated. |
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! Variables local to the procedure: |
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INTEGER N, NE |
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!--------------------------------------- |
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n = assert_eq(size(x), size(f), size(d), "PCHFE_95 n") |
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ne = assert_eq(size(xe), size(fe), "PCHFE_95 ne") |
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call PCHFE(N, X, F, D, 1, SKIP, NE, XE, FE, IERR) |
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end SUBROUTINE PCHFE_95 |
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end module PCHFE_95_m |
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