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70 lines
1.8 KiB
Fortran
70 lines
1.8 KiB
Fortran
SUBROUTINE sla_DVN (V, UV, VM)
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*+
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* - - - -
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* D V N
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* - - - -
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*
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* Normalizes a 3-vector also giving the modulus (double precision)
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*
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* Given:
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* V d(3) vector
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*
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* Returned:
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* UV d(3) unit vector in direction of V
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* VM d modulus of V
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*
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* Notes:
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*
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* 1 If the modulus of V is zero, UV is set to zero as well.
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*
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* 2 To comply with the ANSI Fortran 77 standard, V and UV must be
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* different arrays. However, the routine is coded so as to work
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* properly on most platforms even if this rule is violated.
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*
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* Last revision: 22 July 2004
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*
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* Copyright P.T.Wallace. All rights reserved.
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*
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* License:
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program (see SLA_CONDITIONS); if not, write to the
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* Free Software Foundation, Inc., 59 Temple Place, Suite 330,
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* Boston, MA 02111-1307 USA
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*
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*-
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IMPLICIT NONE
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DOUBLE PRECISION V(3),UV(3),VM
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INTEGER I
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DOUBLE PRECISION W1,W2
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* Modulus.
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W1 = 0D0
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DO I=1,3
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W2 = V(I)
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W1 = W1+W2*W2
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END DO
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W1 = SQRT(W1)
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VM = W1
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* Normalize the vector.
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IF (W1.LE.0D0) W1 = 1D0
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DO I=1,3
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UV(I) = V(I)/W1
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END DO
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END
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