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annotate libcruft/lapack/srscl.f @ 9665:1dba57e9d08d

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use blas_trans_type for xgemm
author Jaroslav Hajek <highegg@gmail.com>
date Sat, 26 Sep 2009 10:41:07 +0200
parents 82be108cc558
children
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1 SUBROUTINE SRSCL( N, SA, SX, INCX )
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2 *
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3 * -- LAPACK auxiliary routine (version 3.1) --
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4 * Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
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5 * November 2006
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6 *
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7 * .. Scalar Arguments ..
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8 INTEGER INCX, N
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9 REAL SA
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10 * ..
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11 * .. Array Arguments ..
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12 REAL SX( * )
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13 * ..
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14 *
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15 * Purpose
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16 * =======
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17 *
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18 * SRSCL multiplies an n-element real vector x by the real scalar 1/a.
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19 * This is done without overflow or underflow as long as
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20 * the final result x/a does not overflow or underflow.
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21 *
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22 * Arguments
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23 * =========
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24 *
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25 * N (input) INTEGER
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26 * The number of components of the vector x.
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27 *
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28 * SA (input) REAL
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29 * The scalar a which is used to divide each component of x.
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30 * SA must be >= 0, or the subroutine will divide by zero.
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31 *
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32 * SX (input/output) REAL array, dimension
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33 * (1+(N-1)*abs(INCX))
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34 * The n-element vector x.
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35 *
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36 * INCX (input) INTEGER
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37 * The increment between successive values of the vector SX.
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38 * > 0: SX(1) = X(1) and SX(1+(i-1)*INCX) = x(i), 1< i<= n
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39 *
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40 * =====================================================================
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41 *
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42 * .. Parameters ..
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43 REAL ONE, ZERO
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44 PARAMETER ( ONE = 1.0E+0, ZERO = 0.0E+0 )
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45 * ..
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46 * .. Local Scalars ..
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47 LOGICAL DONE
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48 REAL BIGNUM, CDEN, CDEN1, CNUM, CNUM1, MUL, SMLNUM
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49 * ..
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50 * .. External Functions ..
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51 REAL SLAMCH
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52 EXTERNAL SLAMCH
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53 * ..
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54 * .. External Subroutines ..
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55 EXTERNAL SLABAD, SSCAL
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56 * ..
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57 * .. Intrinsic Functions ..
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58 INTRINSIC ABS
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59 * ..
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60 * .. Executable Statements ..
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61 *
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62 * Quick return if possible
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63 *
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64 IF( N.LE.0 )
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65 $ RETURN
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66 *
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67 * Get machine parameters
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68 *
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69 SMLNUM = SLAMCH( 'S' )
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70 BIGNUM = ONE / SMLNUM
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71 CALL SLABAD( SMLNUM, BIGNUM )
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72 *
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73 * Initialize the denominator to SA and the numerator to 1.
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74 *
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75 CDEN = SA
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76 CNUM = ONE
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77 *
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78 10 CONTINUE
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79 CDEN1 = CDEN*SMLNUM
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80 CNUM1 = CNUM / BIGNUM
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81 IF( ABS( CDEN1 ).GT.ABS( CNUM ) .AND. CNUM.NE.ZERO ) THEN
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82 *
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83 * Pre-multiply X by SMLNUM if CDEN is large compared to CNUM.
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84 *
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85 MUL = SMLNUM
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86 DONE = .FALSE.
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87 CDEN = CDEN1
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88 ELSE IF( ABS( CNUM1 ).GT.ABS( CDEN ) ) THEN
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89 *
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90 * Pre-multiply X by BIGNUM if CDEN is small compared to CNUM.
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91 *
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92 MUL = BIGNUM
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93 DONE = .FALSE.
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94 CNUM = CNUM1
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95 ELSE
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96 *
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97 * Multiply X by CNUM / CDEN and return.
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98 *
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99 MUL = CNUM / CDEN
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100 DONE = .TRUE.
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101 END IF
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102 *
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103 * Scale the vector X by MUL
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104 *
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105 CALL SSCAL( N, MUL, SX, INCX )
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106 *
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107 IF( .NOT.DONE )
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108 $ GO TO 10
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109 *
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110 RETURN
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111 *
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112 * End of SRSCL
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113 *
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114 END