[blivet:master 03/18] Do not compare the same two values twice.

[Anne Mulhern]

If x and y are Sizes, not (x < y) implies x >= y.

Write out the formula the if-statement implements in a comment, in case
readers of the code do not understand the semantics of elif or Size().

Signed-off-by: mulhern 
---
 blivet/devicelibs/swap.py | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/blivet/devicelibs/swap.py b/blivet/devicelibs/swap.py
index bcc0308..93ae64e 100644
--- a/blivet/devicelibs/swap.py
+++ b/blivet/devicelibs/swap.py
@@ -142,14 +142,20 @@ def swapSuggestion(quiet=False, hibernation=False, disk_space=None):
     eight_GiB = Size("8GiB")
     sixtyfour_GiB = Size("64 GiB")

-    #chart suggested in the discussion with other teams
+    # the succeeding if-statement implements the following formula for
+    # suggested swap size.
+    #
+    # swap(mem) = 2 * mem, if mem < 2 GiB
+    #           = mem,     if 2 GiB <= mem < 8 GiB
+    #           = mem / 2, if 8 GIB <= mem < 64 GiB
+    #           = 4 GiB,   if mem >= 64 GiB
     if mem < two_GiB:
         swap = 2 * mem

-    elif two_GiB <= mem < eight_GiB:
+    elif mem < eight_GiB:
         swap = mem

-    elif eight_GiB <= mem < sixtyfour_GiB:
+    elif mem < sixtyfour_GiB:
         swap = mem / 2

else:

[Vratislav Podzimek]

On Mon, 2015-01-05 at 10:03 -0500, mulhern wrote:
> If x and y are Sizes, not (x < y) implies x >= y.
>
> Write out the formula the if-statement implements in a comment, in case
> readers of the code do not understand the semantics of elif or Size().
> Signed-off-by: mulhern
>
> blivet/devicelibs/swap.py | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/blivet/devicelibs/swap.py b/blivet/devicelibs/swap.py
> index bcc0308..93ae64e 100644
> --- a/blivet/devicelibs/swap.py
> +++ b/blivet/devicelibs/swap.py
> @@ -142,14 +142,20 @@ def swapSuggestion(quiet=False, hibernation=False, disk_space=None):
>      eight_GiB = Size("8GiB")
>      sixtyfour_GiB = Size("64 GiB")
> #chart suggested in the discussion with other teams
> # the succeeding if-statement implements the following formula for
> # suggested swap size.
> #
> # swap(mem) = 2 * mem, if mem < 2 GiB
> #           = mem,     if 2 GiB <= mem < 8 GiB
> #           = mem / 2, if 8 GIB <= mem < 64 GiB
> #           = 4 GiB,   if mem >= 64 GiB
> if mem < two_GiB:
>     swap = 2 * mem
> elif two_GiB <= mem < eight_GiB:
> elif mem < eight_GiB:
>     swap = mem
> elif eight_GiB <= mem < sixtyfour_GiB:
>
> elif mem < sixtyfour_GiB:
>     swap = mem / 2
>
> else:

Looks good to me.