Mercurial > hg > octave-lyh
comparison libcruft/blas/snrm2.f @ 7789:82be108cc558
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> |
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| date | Sun, 27 Apr 2008 22:34:17 +0200 |
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| 7788:45f5faba05a2 | 7789:82be108cc558 |
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| 1 REAL FUNCTION SNRM2(N,X,INCX) | |
| 2 * .. Scalar Arguments .. | |
| 3 INTEGER INCX,N | |
| 4 * .. | |
| 5 * .. Array Arguments .. | |
| 6 REAL X(*) | |
| 7 * .. | |
| 8 * | |
| 9 * Purpose | |
| 10 * ======= | |
| 11 * | |
| 12 * SNRM2 returns the euclidean norm of a vector via the function | |
| 13 * name, so that | |
| 14 * | |
| 15 * SNRM2 := sqrt( x'*x ). | |
| 16 * | |
| 17 * Further Details | |
| 18 * =============== | |
| 19 * | |
| 20 * -- This version written on 25-October-1982. | |
| 21 * Modified on 14-October-1993 to inline the call to SLASSQ. | |
| 22 * Sven Hammarling, Nag Ltd. | |
| 23 * | |
| 24 * | |
| 25 * .. Parameters .. | |
| 26 REAL ONE,ZERO | |
| 27 PARAMETER (ONE=1.0E+0,ZERO=0.0E+0) | |
| 28 * .. | |
| 29 * .. Local Scalars .. | |
| 30 REAL ABSXI,NORM,SCALE,SSQ | |
| 31 INTEGER IX | |
| 32 * .. | |
| 33 * .. Intrinsic Functions .. | |
| 34 INTRINSIC ABS,SQRT | |
| 35 * .. | |
| 36 IF (N.LT.1 .OR. INCX.LT.1) THEN | |
| 37 NORM = ZERO | |
| 38 ELSE IF (N.EQ.1) THEN | |
| 39 NORM = ABS(X(1)) | |
| 40 ELSE | |
| 41 SCALE = ZERO | |
| 42 SSQ = ONE | |
| 43 * The following loop is equivalent to this call to the LAPACK | |
| 44 * auxiliary routine: | |
| 45 * CALL SLASSQ( N, X, INCX, SCALE, SSQ ) | |
| 46 * | |
| 47 DO 10 IX = 1,1 + (N-1)*INCX,INCX | |
| 48 IF (X(IX).NE.ZERO) THEN | |
| 49 ABSXI = ABS(X(IX)) | |
| 50 IF (SCALE.LT.ABSXI) THEN | |
| 51 SSQ = ONE + SSQ* (SCALE/ABSXI)**2 | |
| 52 SCALE = ABSXI | |
| 53 ELSE | |
| 54 SSQ = SSQ + (ABSXI/SCALE)**2 | |
| 55 END IF | |
| 56 END IF | |
| 57 10 CONTINUE | |
| 58 NORM = SCALE*SQRT(SSQ) | |
| 59 END IF | |
| 60 * | |
| 61 SNRM2 = NORM | |
| 62 RETURN | |
| 63 * | |
| 64 * End of SNRM2. | |
| 65 * | |
| 66 END |