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diff libcruft/slatec-fn/atanh.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
parents
children d17237256856
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--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libcruft/slatec-fn/atanh.f	Sun Apr 27 22:34:17 2008 +0200
@@ -0,0 +1,72 @@
+*DECK ATANH
+      FUNCTION ATANH (X)
+C***BEGIN PROLOGUE  ATANH
+C***PURPOSE  Compute the arc hyperbolic tangent.
+C***LIBRARY   SLATEC (FNLIB)
+C***CATEGORY  C4C
+C***TYPE      SINGLE PRECISION (ATANH-S, DATANH-D, CATANH-C)
+C***KEYWORDS  ARC HYPERBOLIC TANGENT, ATANH, ELEMENTARY FUNCTIONS,
+C             FNLIB, INVERSE HYPERBOLIC TANGENT
+C***AUTHOR  Fullerton, W., (LANL)
+C***DESCRIPTION
+C
+C ATANH(X) computes the arc hyperbolic tangent of X.
+C
+C Series for ATNH       on the interval  0.          to  2.50000D-01
+C                                        with weighted error   6.70E-18
+C                                         log weighted error  17.17
+C                               significant figures required  16.01
+C                                    decimal places required  17.76
+C
+C***REFERENCES  (NONE)
+C***ROUTINES CALLED  CSEVL, INITS, R1MACH, XERMSG
+C***REVISION HISTORY  (YYMMDD)
+C   770401  DATE WRITTEN
+C   890531  Changed all specific intrinsics to generic.  (WRB)
+C   890531  REVISION DATE from Version 3.2
+C   891214  Prologue converted to Version 4.0 format.  (BAB)
+C   900315  CALLs to XERROR changed to CALLs to XERMSG.  (THJ)
+C   900326  Removed duplicate information from DESCRIPTION section.
+C           (WRB)
+C***END PROLOGUE  ATANH
+      DIMENSION ATNHCS(15)
+      LOGICAL FIRST
+      SAVE ATNHCS, NTERMS, DXREL, SQEPS, FIRST
+      DATA ATNHCS( 1) /    .0943951023 93195492E0 /
+      DATA ATNHCS( 2) /    .0491984370 55786159E0 /
+      DATA ATNHCS( 3) /    .0021025935 22455432E0 /
+      DATA ATNHCS( 4) /    .0001073554 44977611E0 /
+      DATA ATNHCS( 5) /    .0000059782 67249293E0 /
+      DATA ATNHCS( 6) /    .0000003505 06203088E0 /
+      DATA ATNHCS( 7) /    .0000000212 63743437E0 /
+      DATA ATNHCS( 8) /    .0000000013 21694535E0 /
+      DATA ATNHCS( 9) /    .0000000000 83658755E0 /
+      DATA ATNHCS(10) /    .0000000000 05370503E0 /
+      DATA ATNHCS(11) /    .0000000000 00348665E0 /
+      DATA ATNHCS(12) /    .0000000000 00022845E0 /
+      DATA ATNHCS(13) /    .0000000000 00001508E0 /
+      DATA ATNHCS(14) /    .0000000000 00000100E0 /
+      DATA ATNHCS(15) /    .0000000000 00000006E0 /
+      DATA FIRST /.TRUE./
+C***FIRST EXECUTABLE STATEMENT  ATANH
+      IF (FIRST) THEN
+         NTERMS = INITS (ATNHCS, 15, 0.1*R1MACH(3))
+         DXREL = SQRT (R1MACH(4))
+         SQEPS = SQRT (3.0*R1MACH(3))
+      ENDIF
+      FIRST = .FALSE.
+C
+      Y = ABS(X)
+      IF (Y .GE. 1.0) CALL XERMSG ('SLATEC', 'ATANH', 'ABS(X) GE 1', 2,
+     +   2)
+C
+      IF (1.0-Y .LT. DXREL) CALL XERMSG ('SLATEC', 'ATANH',
+     +   'ANSWER LT HALF PRECISION BECAUSE ABS(X) TOO NEAR 1', 1, 1)
+C
+      ATANH = X
+      IF (Y.GT.SQEPS .AND. Y.LE.0.5) ATANH = X*(1.0 + CSEVL (8.*X*X-1.,
+     1  ATNHCS, NTERMS))
+      IF (Y.GT.0.5) ATANH = 0.5*LOG((1.0+X)/(1.0-X))
+C
+      RETURN
+      END