cswap.f (2860B)
1 !> 2 ! @license Apache-2.0 3 ! 4 ! Copyright (c) 2020 The Stdlib Authors. 5 ! 6 ! Licensed under the Apache License, Version 2.0 (the "License"); 7 ! you may not use this file except in compliance with the License. 8 ! You may obtain a copy of the License at 9 ! 10 ! http://www.apache.org/licenses/LICENSE-2.0 11 ! 12 ! Unless required by applicable law or agreed to in writing, software 13 ! distributed under the License is distributed on an "AS IS" BASIS, 14 ! WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 15 ! See the License for the specific language governing permissions and 16 ! limitations under the License. 17 !< 18 19 !> Interchanges two complex single-precision floating-point vectors. 20 ! 21 ! ## Notes 22 ! 23 ! * Modified version of reference BLAS level1 routine (version 3.9.0). Updated to "free form" Fortran 95. 24 ! 25 ! ## Authors 26 ! 27 ! * Univ. of Tennessee 28 ! * Univ. of California Berkeley 29 ! * Univ. of Colorado Denver 30 ! * NAG Ltd. 31 ! 32 ! ## History 33 ! 34 ! * Jack Dongarra, linpack, 3/11/78. 35 ! 36 ! - modified 12/3/93, array(1) declarations changed to array(*) 37 ! 38 ! ## License 39 ! 40 ! From <http://netlib.org/blas/faq.html>: 41 ! 42 ! > The reference BLAS is a freely-available software package. It is available from netlib via anonymous ftp and the World Wide Web. Thus, it can be included in commercial software packages (and has been). We only ask that proper credit be given to the authors. 43 ! > 44 ! > Like all software, it is copyrighted. It is not trademarked, but we do ask the following: 45 ! > 46 ! > * If you modify the source for these routines we ask that you change the name of the routine and comment the changes made to the original. 47 ! > 48 ! > * We will gladly answer any questions regarding the software. If a modification is done, however, it is the responsibility of the person who modified the routine to provide support. 49 ! 50 ! @param {integer} N - number of values to swap 51 ! @param {Array<complex>} cx - first input array 52 ! @param {integer} strideX - `cx` stride length 53 ! @param {Array<complex>} cy - second input array 54 ! @param {integer} strideY - `cy` stride length 55 !< 56 subroutine cswap( N, cx, strideX, cy, strideY ) 57 implicit none 58 ! .. 59 ! Scalar arguments: 60 integer :: strideX, strideY, N 61 ! .. 62 ! Array arguments: 63 complex :: cx(*), cy(*) 64 ! .. 65 ! Local scalars: 66 integer :: ix, iy, i 67 complex :: tmp 68 ! .. 69 if ( N <= 0 ) then 70 return 71 end if 72 ! .. 73 if ( strideX == 1 .AND. strideY == 1 ) then 74 do i = 1, N 75 tmp = cx( i ) 76 cx( i ) = cy( i ) 77 cy( i ) = tmp 78 end do 79 else 80 if ( strideX < 0 ) then 81 ix = ((1-N)*strideX) + 1 82 else 83 ix = 1 84 end if 85 if ( strideY < 0 ) then 86 iy = ((1-N)*strideY) + 1 87 else 88 iy = 1 89 end if 90 do i = 1, N 91 tmp = cx( ix ) 92 cx( ix ) = cy( iy ) 93 cy( iy ) = tmp 94 ix = ix + strideX 95 iy = iy + strideY 96 end do 97 end if 98 return 99 end subroutine cswap