87 lines
2.3 KiB
FortranFixed
87 lines
2.3 KiB
FortranFixed
SUBROUTINE SLAR2V( N, X, Y, Z, INCX, C, S, INCC )
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*
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* -- LAPACK auxiliary routine (version 3.1) --
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* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
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* November 2006
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*
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* .. Scalar Arguments ..
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INTEGER INCC, INCX, N
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* ..
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* .. Array Arguments ..
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REAL C( * ), S( * ), X( * ), Y( * ), Z( * )
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* ..
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*
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* Purpose
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* =======
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*
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* SLAR2V applies a vector of real plane rotations from both sides to
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* a sequence of 2-by-2 real symmetric matrices, defined by the elements
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* of the vectors x, y and z. For i = 1,2,...,n
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*
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* ( x(i) z(i) ) := ( c(i) s(i) ) ( x(i) z(i) ) ( c(i) -s(i) )
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* ( z(i) y(i) ) ( -s(i) c(i) ) ( z(i) y(i) ) ( s(i) c(i) )
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*
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* Arguments
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* =========
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*
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* N (input) INTEGER
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* The number of plane rotations to be applied.
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*
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* X (input/output) REAL array,
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* dimension (1+(N-1)*INCX)
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* The vector x.
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*
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* Y (input/output) REAL array,
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* dimension (1+(N-1)*INCX)
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* The vector y.
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*
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* Z (input/output) REAL array,
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* dimension (1+(N-1)*INCX)
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* The vector z.
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*
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* INCX (input) INTEGER
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* The increment between elements of X, Y and Z. INCX > 0.
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*
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* C (input) REAL array, dimension (1+(N-1)*INCC)
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* The cosines of the plane rotations.
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*
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* S (input) REAL array, dimension (1+(N-1)*INCC)
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* The sines of the plane rotations.
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*
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* INCC (input) INTEGER
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* The increment between elements of C and S. INCC > 0.
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*
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* =====================================================================
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*
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* .. Local Scalars ..
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INTEGER I, IC, IX
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REAL CI, SI, T1, T2, T3, T4, T5, T6, XI, YI, ZI
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* ..
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* .. Executable Statements ..
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*
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IX = 1
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IC = 1
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DO 10 I = 1, N
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XI = X( IX )
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YI = Y( IX )
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ZI = Z( IX )
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CI = C( IC )
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SI = S( IC )
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T1 = SI*ZI
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T2 = CI*ZI
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T3 = T2 - SI*XI
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T4 = T2 + SI*YI
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T5 = CI*XI + T1
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T6 = CI*YI - T1
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X( IX ) = CI*T5 + SI*T4
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Y( IX ) = CI*T6 - SI*T3
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Z( IX ) = CI*T4 - SI*T5
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IX = IX + INCX
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IC = IC + INCC
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10 CONTINUE
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*
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* End of SLAR2V
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*
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RETURN
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END
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