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2608
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1 subroutine drot (n,dx,incx,dy,incy,c,s) |
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2 c |
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3 c applies a plane rotation. |
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4 c jack dongarra, linpack, 3/11/78. |
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5 c modified 12/3/93, array(1) declarations changed to array(*) |
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6 c |
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7 double precision dx(*),dy(*),dtemp,c,s |
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8 integer i,incx,incy,ix,iy,n |
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9 c |
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10 if(n.le.0)return |
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11 if(incx.eq.1.and.incy.eq.1)go to 20 |
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12 c |
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13 c code for unequal increments or equal increments not equal |
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14 c to 1 |
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15 c |
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16 ix = 1 |
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17 iy = 1 |
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18 if(incx.lt.0)ix = (-n+1)*incx + 1 |
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19 if(incy.lt.0)iy = (-n+1)*incy + 1 |
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20 do 10 i = 1,n |
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21 dtemp = c*dx(ix) + s*dy(iy) |
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22 dy(iy) = c*dy(iy) - s*dx(ix) |
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23 dx(ix) = dtemp |
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24 ix = ix + incx |
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25 iy = iy + incy |
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26 10 continue |
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27 return |
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28 c |
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29 c code for both increments equal to 1 |
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30 c |
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31 20 do 30 i = 1,n |
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32 dtemp = c*dx(i) + s*dy(i) |
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33 dy(i) = c*dy(i) - s*dx(i) |
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34 dx(i) = dtemp |
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35 30 continue |
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36 return |
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37 end |
