Which is more effective? Switch vs. Loop

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Hi all,

Just a quick question.... in general (and in C# if that's relevant) is a switch more effective than a loop or the other way 'round? Thanks!

Posted 17-Jan-12 2:43am

Hypermommy

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BillWoodruff 17-Jan-12 9:49am

Well, that's a "provocative question" ... which can be a good thing ... but, I think in order to reply to this question: you need to tell us a scenario in which the purpose and behavior of the code in both the switch statement, and whatever flavor of 'loop' you are using, is identical !

And, I can't quite imagine what that would be.

Richard MacCutchan 17-Jan-12 9:59am

Despite deleting your comments below, I don't think you do understand the basic difference. Try explaining your problem and why you think it can be solved by either a switch block or a loop.

johannesnestler 17-Jan-12 10:13am

switch vs. loop? Are you shure you understand your question? It's like I'd ask whats more effective: cars or rain ... (There is no obvious relation - please clarify what you mean)

Hypermommy 17-Jan-12 11:33am

Okay... so I've got this function that is currently written like this:

switch (searchFacilitator_.GroupType)
{
case BRGroupTypeIds.Audit:
rowCount = mapper.ResultByRowcountForGroupSearch(searchFacilitator_.SetId,
GroupSearchBatchStrings.AUDIT_TEMPSPACE_NAME,
(DataAccessContext) dac_.Clone());
return rowCount;
break;
case BRGroupTypeIds.BusAcctMaster:
rowCount = mapper.ResultByRowcountForGroupSearch(searchFacilitator_.SetId,
GroupSearchBatchStrings.BUSACCTMASTER_TEMPSPACE_NAME,
(DataAccessContext) dac_.Clone());
return rowCount;
break;
case BRGroupTypeIds.Lic:
rowCount = mapper.ResultByRowcountForGroupSearch(searchFacilitator_.SetId,
GroupSearchBatchStrings.LIC_TEMPSPACE_NAME,
(DataAccessContext) dac_.Clone());
return rowCount;
break;
case BRGroupTypeIds.LicBill:
rowCount = mapper.ResultByRowcountForGroupSearch(searchFacilitator_.SetId,
GroupSearchBatchStrings.LICBILL_TEMPSPACE_NAME,
(DataAccessContext) dac_.Clone());
return rowCount;
break;
case BRGroupTypeIds.TTA:
rowCount = mapper.ResultByRowcountForGroupSearch(searchFacilitator_.SetId,
GroupSearchBatchStrings.TTA_TEMPSPACE_NAME,
(DataAccessContext) dac_.Clone());
return rowCount;
break;
case BRGroupTypeIds.TTR:
rowCount = mapper.ResultByRowcountForGroupSearch(searchFacilitator_.SetId,
GroupSearchBatchStrings.TTR_TEMPSPACE_NAME,
(DataAccessContext) dac_.Clone());
return rowCount;
break;
case BRGroupTypeIds.TTRBill:
rowCount = mapper.ResultByRowcountForGroupSearch(searchFacilitator_.SetId,
GroupSearchBatchStrings.TTRBILL_TEMPSPACE_NAME,
(DataAccessContext) dac_.Clone());
return rowCount;
break;
default:
return 0;
}

This feeds into a dynamically build SQL statement.

But I could write it like this:

foreach (int TempspaceName in GroupSearchBatchStrings)
{
if (TempspaceName = searchFacilitator_.GroupType)
{
mapper.ResultByRowcountForGroupSearch((searchFacilitator_.SetId, TempspaceName, dac))
}
}

Of course, I'd have to modify some of what's going on downstream to handle the fact that we're sending in an integer, not a string, but I could do that.

So, basically, I'm trying to figure out which is generally more effective, a switch or a loop.

Richard MacCutchan 17-Jan-12 11:41am

The difference will be so small as to be unimportant and probably only measurable in micro-seconds or smaller. I would suggest you use the one that is more readable and so makes most sense to a support engineer who may have the job of maintaining it in the future.

Hypermommy 17-Jan-12 12:59pm

Thanks everyone!

2 solutions

Solution 1

they are 2 different things..

you can(should) use switch in order to avoid multple if-else statements

there is only one single code execution

loops like for or foreach repeteat the code n times

Posted 17-Jan-12 2:47am

nrgjack

Updated 17-Jan-12 2:48am

v2

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BobJanova · Accepted Answer · 2012-01-17T05:58:00

Okay having read your comment, you should use a formulation that allows you not to repeat things.

What you're actually trying to do is

return mapper.ResultByRowcountForGroupSearch(searchFacilitator_.SetId,
                                                           x,
                                                           dac);

... where x is set based on the group type.

So I recommend you set up a Dictionary<int, string> (your group types are int I think?), and populate it either statically or in the constructor of the enclosing class (probably statically if the mappings are something you can write in at compile time), e.g.:

static Dictionary<int, string> groupTypeMap = new Dictionary<int, string>();
static ClassName(){ // static constructor
 groupTypeMap[BRGroupTypeIds.Audit] = GroupSearchBatchStrings.AUDIT_TEMPSPACE_NAME;
 // etc
}

Then in the method that you're asking about, you can do

return mapper.ResultByRowcountForGroupSearch(searchFacilitator_.SetId,
                                                           groupTypeMap[searchFacilitator_.GroupType,
                                                           dac);

... or, if it's possible to not be in a group and you don't want an exception from the lookup (i.e. the actual equivalent of your switch statement):

string typeName;
return groupTypeMap.TryGetValue(searchFacilitator_.GroupType, out typeName) ?
 mapper.ResultByRowcountForGroupSearch(searchFacilitator_.SetId, typename, dac) :
 0;