Re: timings II. const varying vs value varying

[Scott Klement <klemscot@xxxxxxxxxxxx>]

When something is passed "const" the system passes a pointer to the
data...  i.e. it has to copy 16 bytes.   (Unless, you pass an expression
or something like that, in which case it has to allocate memory, put
the value of the expression into that memory...  but it still passes
only the address of the temp memory)

However, when something is passed "value" it has to make a copy of the
entire variable.

So, logically, it will take longer to pass something large by value
than it would by const.   i.e. copyying 16 bytes is faster than copying
32,000.



On Tue, 8 Oct 2002, Steve Richter wrote:

> here is a performance discrepancy that happens when a string arg is passed
> "const varying" ( fast ) vs "value varying" ( slow ).
>
>
> ** arg1 is value varying.
>  pTestFunc1        b
>  dTestFunc1        pi            10a
>  d InString                   32000a   value varying
>  c                   return    'efg'
>  p                 e
>
> ** arg1 is const varying.
>  pTestFunc2        b
>  dTestFunc2        pi            10a
>  d InString                   32000a   const varying
>  c                   return    'efg'
>  p                 e
>
>  d rv              s             10a
>  d ch80            s             80a   varying
>
> ** runs slow. 9663 milliseconds to do 50,000 calls.
>  c                   eval      rv = TestFunc1( ch80 )
>  c                   eval      rv = TestFunc2( ch80 )
>
> ** runs fast. 73 milliseconds to do 50,000 calls.
>  c                   eval      rv = TestFunc1( ch80 )
>  c                   eval      rv = TestFunc2( ch80 )
>
> why the speed difference?
>
> Steve Richter
>