Re: Who uses clapack?notions to pastures.

From: Gordon Sande (g.sande_at_worldnet.att.net)
Date: 12/12/04 

Date: Sun, 12 Dec 2004 20:51:46 GMT

Jentje Goslinga wrote:
>
>
> Gerry Thomas wrote:
>
>> "Jentje Goslinga" <goslinga@telus.net> wrote in message
>> news:41BA59EC.2050208@telus.net...

[snip]

>
> No understanding of how computers function which is
> apparent from clever attempts at optimization such as:
>
> I1 = I+1
>
> Let's say the compiler already has "I" in a register
> and now has to allocate a stack variable (in cache memory)
> to hold an extra variable and move this integer from
> the stack to save a single cycle a few times.
>

Perhaps what they were optimizing was the number of compiler
error messages. It is well known that programs are much more
efficient when the number of compiler error messages is zero.

When dinosaurs were current the statement

   do 10 i = 1, n + 1

drew a diagnostic about bad syntax so the result was

   n1 = n + 1
   do 10 i = 1, n1

The underlying cause was an attempt by the compiler writers, in their
role as language designers, to make use of the machines which they had
access to. Those machines had vary fast caches as the memory and
processor speeds were about the same. No extra cost for memory latency
as the cache did not get in the way. The cache was quite inexpensive
as it consisted of a length of copper wire on the backplane.

[snip]

>
> Jentje Goslinga
>

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