Bug#848246: [Debian-science-sagemath] Fwd: sagemath_7.4-1_amd64.changes is NEW

[Ximin Luo]

Control: retitle -1 Document SYMPOW_CACHEDIR better and automatically try to create it

Jerome BENOIT:
> Hello SymPow enthusiasts,
> 
> On 17/12/16 15:46, Jerome BENOIT wrote:
>>> It would be good if sympow could automatically create SYMPOW_CACHEDIR
>>>> if it doesn't exist. Otherwise, I would have to add this logic to
>>>> Sage, which seems a bit unclean.
>> I not so sure that it is a good idea to create SYMPOW_CACHEDIR on the fly.
>> Not that if SYMPOW_CACHEDIR does not exist, an appropraite message is printed.
> 
>>>
> I am on my way to add a mechanism to create SYMPOW_CACHEDIR on the fly
> (that may avoid to add a dirty trick on Sage).
> 

Hey, thanks for this. To explain in some more detail: at the moment I have to patch Sage like this:

sage/src/sage/lfunctions/sympow.py:
-        cmd = 'sympow %s'%args
+        cmd = 'env HOME="%s" sympow %s' % (DOT_SAGE, args)

Setting HOME is ugly, it would be nicer to do this instead:

-        cmd = 'sympow %s'%args
+        cmd = 'env SYMPOW_CACHEDIR="%s" sympow %s' % (os.path.join(DOT_SAGE, "sympow"), args)

However I can't, because sympow does not automatically create SYMPOW_CACHEDIR. I would have to do this instead:

-        cmd = 'sympow %s'%args
+        cmd = 'mkdir "{0}" && env SYMPOW_CACHEDIR="{0}" sympow {1}'.format(os.path.join(DOT_SAGE, "sympow"), args)

Note, it's not necessary to create all the parent directories like what `mkdir -p` does. That is, if `dirname $SYMPOW_CACHEDIR` does not exist, I think it's fine that sympow fails - because there is no way to know what permissions (etc) to create parent directories with, it is a sysadmin and local policy issue, and it means there is a bug somewhere else.

However if `dirname $SYMPOW_CACHEDIR` does exist, then sympow should try to create SYMPOW_CACHEDIR inside it - it "controls" this directory, so it knows what permissions to use.

So actually, I think there is no bug in sympow regarding non-existent HOME. It is OK to fail, if HOME does not exist and SYMPOW_CACHEDIR is not set. It is better that during tests, SYMPOW_CACHEDIR is set explicitly in a Makefile, or by the parent process (Sage) which already has a "directory for testing" (DOT_SAGE).

X

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