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*DECK LIBLEX
SUBROUTINE LIBLEX(NELE,PNTE,ELMT,NOTX,TERP)
*
*-----------------------------------------------------------------------
*
*Purpose:
* Compute factors for Lagrangian interpolation.
*
*Copyright:
* Copyright (C) 2002 Ecole Polytechnique de Montreal
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version
*
*Author(s): A. Hebert and G. Marleau
*
*Parameters: input
* NELE number of elements in table.
* PNTE extrapolation point.
* ELMT values of elements in table.
* NOTX order of interpolation:
* >0 order NOTX in square root of PNTE;
* <0 order -NOTX in PNTE.
*
*Parameters: output
* TERP extrapolation factor.
*
*-----------------------------------------------------------------------
*
*----
* SUBROUTINE ARGUMENTS
*----
INTEGER NELE,NOTX
REAL PNTE,ELMT(NELE)
DOUBLE PRECISION TERP(NELE)
*----
* LOCAL VARIABLES
*----
DOUBLE PRECISION FACTOR,TERM,SQPNTE
*
I1=1
I2=NELE
NORD=ABS(NOTX)
TERP(:NELE)=0.0D0
DO 100 I=1,NELE
IF(PNTE.EQ.ELMT(I)) THEN
TERP(I)=1.0D0
RETURN
ELSE IF(PNTE.GT.ELMT(I)) THEN
I1=MAX(I-(NORD-1)/2,I1)
ELSE IF(PNTE.LT.ELMT(I)) THEN
I2=MIN(I+(NORD-1)/2,I2)
ENDIF
100 CONTINUE
*
IF(I1.EQ.1) THEN
I2=MIN(NELE,NORD+1)
ELSE IF(I2.EQ.NELE) THEN
I1=MAX(1,NELE-NORD)
ENDIF
FACTOR=1.0D0
IF(NOTX.LT.0) THEN
SQPNTE=DBLE(PNTE)
DO 110 I=I1,I2
IF(ABS(PNTE-ELMT(I)).LE.1.0E-5*ABS(PNTE)) THEN
TERP(I)=1.0D0
RETURN
ENDIF
FACTOR=FACTOR*( SQPNTE-DBLE(ELMT(I)) )
110 CONTINUE
DO 120 I=I1,I2
TERM=FACTOR/( SQPNTE-DBLE(ELMT(I)) )
DO 130 J=I1,I2
IF(I.NE.J) TERM=TERM/
> ( DBLE(ELMT(I))-DBLE(ELMT(J)) )
130 CONTINUE
TERP(I)=TERM
120 CONTINUE
ELSE
SQPNTE=DBLE(SQRT(PNTE))
DO 160 I=I1,I2
IF(ABS(PNTE-ELMT(I)).LE.1.0E-5*ABS(PNTE)) THEN
TERP(I)=1.0D0
RETURN
ENDIF
FACTOR=FACTOR*( SQPNTE-DBLE(SQRT(ELMT(I))) )
160 CONTINUE
DO 170 I=I1,I2
TERM=FACTOR/( SQPNTE-DBLE(SQRT(ELMT(I))) )
DO 180 J=I1,I2
IF(I.NE.J) TERM=TERM/
> ( DBLE(SQRT(ELMT(I)))-DBLE(SQRT(ELMT(J))) )
180 CONTINUE
TERP(I)=TERM
170 CONTINUE
ENDIF
RETURN
END
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