Adding useful dlmach help in order to know for what purpose this function is used.

1 files changed, 39 insertions, 0 deletions

diff --git a/Doc/Elementary Functions/dlamch.help b/Doc/Elementary Functions/dlamch.help
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+/*  -- LAPACK auxiliary routine (version 3.0) --
+       Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,
+       Courant Institute, Argonne National Lab, and Rice University
+       October 31, 1992
+
+
+    Purpose
+    =======
+
+    DLAMCH determines double precision machine parameters.
+
+    Arguments
+    =========
+
+    CMACH   (input) CHARACTER*1
+            Specifies the value to be returned by DLAMCH:
+            = 'E' or 'e',   DLAMCH := eps
+            = 'S' or 's ,   DLAMCH := sfmin
+            = 'B' or 'b',   DLAMCH := base
+            = 'P' or 'p',   DLAMCH := eps*base
+            = 'N' or 'n',   DLAMCH := t
+            = 'R' or 'r',   DLAMCH := rnd
+            = 'M' or 'm',   DLAMCH := emin
+            = 'U' or 'u',   DLAMCH := rmin
+            = 'L' or 'l',   DLAMCH := emax
+            = 'O' or 'o',   DLAMCH := rmax
+
+            where
+
+            eps   = relative machine precision
+            sfmin = safe minimum, such that 1/sfmin does not overflow
+            base  = base of the machine
+            prec  = eps*base
+            t     = number of (base) digits in the mantissa
+            rnd   = 1.0 when rounding occurs in addition, 0.0 otherwise
+            emin  = minimum exponent before (gradual) underflow
+            rmin  = underflow threshold - base**(emin-1)
+            emax  = largest exponent before overflow
+            rmax  = overflow threshold  - (base**emax)*(1-eps)
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