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annotate libcruft/blas/scnrm2.f @ 7789:82be108cc558

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First attempt at single precision tyeps * * * corrections to qrupdate single precision routines * * * prefer demotion to single over promotion to double * * * Add single precision support to log2 function * * * Trivial PROJECT file update * * * Cache optimized hermitian/transpose methods * * * Add tests for tranpose/hermitian and ChangeLog entry for new transpose code
author David Bateman <dbateman@free.fr>
date Sun, 27 Apr 2008 22:34:17 +0200
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1 REAL FUNCTION SCNRM2(N,X,INCX)
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2 * .. Scalar Arguments ..
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3 INTEGER INCX,N
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4 * ..
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5 * .. Array Arguments ..
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6 COMPLEX X(*)
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7 * ..
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8 *
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9 * Purpose
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10 * =======
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11 *
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12 * SCNRM2 returns the euclidean norm of a vector via the function
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13 * name, so that
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14 *
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15 * SCNRM2 := sqrt( conjg( x' )*x )
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16 *
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17 *
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18 *
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19 * -- This version written on 25-October-1982.
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20 * Modified on 14-October-1993 to inline the call to CLASSQ.
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21 * Sven Hammarling, Nag Ltd.
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22 *
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23 *
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24 * .. Parameters ..
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25 REAL ONE,ZERO
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26 PARAMETER (ONE=1.0E+0,ZERO=0.0E+0)
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27 * ..
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28 * .. Local Scalars ..
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29 REAL NORM,SCALE,SSQ,TEMP
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30 INTEGER IX
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31 * ..
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32 * .. Intrinsic Functions ..
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33 INTRINSIC ABS,AIMAG,REAL,SQRT
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34 * ..
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35 IF (N.LT.1 .OR. INCX.LT.1) THEN
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36 NORM = ZERO
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37 ELSE
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38 SCALE = ZERO
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39 SSQ = ONE
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40 * The following loop is equivalent to this call to the LAPACK
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41 * auxiliary routine:
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42 * CALL CLASSQ( N, X, INCX, SCALE, SSQ )
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43 *
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44 DO 10 IX = 1,1 + (N-1)*INCX,INCX
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45 IF (REAL(X(IX)).NE.ZERO) THEN
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46 TEMP = ABS(REAL(X(IX)))
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47 IF (SCALE.LT.TEMP) THEN
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48 SSQ = ONE + SSQ* (SCALE/TEMP)**2
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49 SCALE = TEMP
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50 ELSE
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51 SSQ = SSQ + (TEMP/SCALE)**2
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52 END IF
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53 END IF
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54 IF (AIMAG(X(IX)).NE.ZERO) THEN
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55 TEMP = ABS(AIMAG(X(IX)))
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56 IF (SCALE.LT.TEMP) THEN
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57 SSQ = ONE + SSQ* (SCALE/TEMP)**2
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58 SCALE = TEMP
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59 ELSE
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60 SSQ = SSQ + (TEMP/SCALE)**2
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61 END IF
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62 END IF
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63 10 CONTINUE
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64 NORM = SCALE*SQRT(SSQ)
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65 END IF
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66 *
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67 SCNRM2 = NORM
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68 RETURN
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69 *
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70 * End of SCNRM2.
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71 *
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72 END