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Diffstat (limited to '2.3-1/src/fortran/lapack/izmax1.f')
| -rw-r--r-- | 2.3-1/src/fortran/lapack/izmax1.f | 95 |
1 files changed, 95 insertions, 0 deletions
diff --git a/2.3-1/src/fortran/lapack/izmax1.f b/2.3-1/src/fortran/lapack/izmax1.f new file mode 100644 index 00000000..7ebffee3 --- /dev/null +++ b/2.3-1/src/fortran/lapack/izmax1.f @@ -0,0 +1,95 @@ + INTEGER FUNCTION IZMAX1( N, CX, INCX ) +* +* -- LAPACK auxiliary routine (version 3.1) -- +* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. +* November 2006 +* +* .. Scalar Arguments .. + INTEGER INCX, N +* .. +* .. Array Arguments .. + COMPLEX*16 CX( * ) +* .. +* +* Purpose +* ======= +* +* IZMAX1 finds the index of the element whose real part has maximum +* absolute value. +* +* Based on IZAMAX from Level 1 BLAS. +* The change is to use the 'genuine' absolute value. +* +* Contributed by Nick Higham for use with ZLACON. +* +* Arguments +* ========= +* +* N (input) INTEGER +* The number of elements in the vector CX. +* +* CX (input) COMPLEX*16 array, dimension (N) +* The vector whose elements will be summed. +* +* INCX (input) INTEGER +* The spacing between successive values of CX. INCX >= 1. +* +* ===================================================================== +* +* .. Local Scalars .. + INTEGER I, IX + DOUBLE PRECISION SMAX + COMPLEX*16 ZDUM +* .. +* .. Intrinsic Functions .. + INTRINSIC ABS +* .. +* .. Statement Functions .. + DOUBLE PRECISION CABS1 +* .. +* .. Statement Function definitions .. +* +* NEXT LINE IS THE ONLY MODIFICATION. + CABS1( ZDUM ) = ABS( ZDUM ) +* .. +* .. Executable Statements .. +* + IZMAX1 = 0 + IF( N.LT.1 ) + $ RETURN + IZMAX1 = 1 + IF( N.EQ.1 ) + $ RETURN + IF( INCX.EQ.1 ) + $ GO TO 30 +* +* CODE FOR INCREMENT NOT EQUAL TO 1 +* + IX = 1 + SMAX = CABS1( CX( 1 ) ) + IX = IX + INCX + DO 20 I = 2, N + IF( CABS1( CX( IX ) ).LE.SMAX ) + $ GO TO 10 + IZMAX1 = I + SMAX = CABS1( CX( IX ) ) + 10 CONTINUE + IX = IX + INCX + 20 CONTINUE + RETURN +* +* CODE FOR INCREMENT EQUAL TO 1 +* + 30 CONTINUE + SMAX = CABS1( CX( 1 ) ) + DO 40 I = 2, N + IF( CABS1( CX( I ) ).LE.SMAX ) + $ GO TO 40 + IZMAX1 = I + SMAX = CABS1( CX( I ) ) + 40 CONTINUE + RETURN +* +* End of IZMAX1 +* + END |