Virtual Pascal: BlockRead open files (sharedenynone?)

[Robert Prins]

Does anyone know what I need to do to BlockRead a file that's currently open?
Normal Read(Ln) doesn't seem to care, but BlockRead gives me an error 32.

Basically, I need to make corrections to the open file, based on what the
error-checking program returns. I can save and close it every time, but keeping
it open (after doing a save) is more convenient.

And if you're puzzled? I've actually got a routine that replaces ReadLn with
"read_ln", which reads directly from a text file read by BlockRead - just as my
"write_line" bypasses "WriteLn" and writes directly to the large-enough
SetTextBuf allocated file buffer...

All part of a process to convert a Pascal program into pure assembler, which has
now reached the stage where all code is actually in-line assembler, making the
program rather a lot smaller, and about three times as fast. ;)

[Jim Leonard]

Post by Robert Prins
Does anyone know what I need to do to BlockRead a file that's currently open?
Normal Read(Ln) doesn't seem to care, but BlockRead gives me an error 32.

...

Post by Robert Prins
All part of a process to convert a Pascal program into pure assembler, which has
now reached the stage where all code is actually in-line assembler, making the
program rather a lot smaller, and about three times as fast. ;)

This feels an awful lot like a question you could answer yourself. In fact, I'll bet you already have...

[r***@gmail.com]

Hi,

Post by Jim Leonard

Post by Robert Prins
All part of a process to convert a Pascal program into pure assembler, which has
now reached the stage where all code is actually in-line assembler, making the
program rather a lot smaller, and about three times as fast. ;)

This feels an awful lot like a question you could answer yourself. In fact, I'll bet you already have...

Not feeling very helpful today, are we, Jim? ;-)


Robert, I've not looked at your code. In fact, I somewhat doubt I
could help. (I don't really understand FPU/SSE.) But since you claim
you have a pure Pascal version, I would indeed be curious to run it
(preferably in pure DOS). Then again, I think you said it runs in
less than a second, which is hardly a worthwhile benchmark.

Just to explain, I've recently tested some compilers (GPC, FPC, TP55,
VP21) and various high-level tricks to optimize their output. Nothing
fancy, just mild curiosity.

For GPC, the obvious answer is attribute(inline) or let it do it
automatically with either -finline-functions or -O3.

FPC needs "inline" function directive (and -Si). I've seen you
complain about FPC before, but it matches (GCC 3.4.6 / 2005) GPC
in output speed nowadays. Seriously, I would reconsider and try
FPC again. It's very good.

TP55 (and similar) are too old but still work fine. There are
various speedups available there, but of course there are better
compilers nowadays, too.

I think you said Virtual Pascal is slow and generates lousy code.
Not quite true. Sure, it doesn't go past 586, but it's not really
slow. It also has the (Delphi-ish) inline function directive
(same as FPC) but in much more limited functionality, so it's not
nearly as useful. Still, it can help a lot.

The other problem I noticed is that VP does indeed claim to
use (186+) ENTER/LEAVE for nested procs. The docs said that
was for 586, but AFAIK that is for all targets (386, 486, 586).
The docs say it was faster on an actual 586. But I've seen this
problem before. On my Core i5 (admittedly somewhat old, Nehalem
Westmere), that kind of code, when heavily used, is actually
four times slower than the older 8086 equivalent. So try
"flattening" your source to avoid nested procedures (move
them to global scope) and re-benchmark it. It really helps!

[Marco van de Voort]

Post by Robert Prins
Does anyone know what I need to do to BlockRead a file that's currently open?
Normal Read(Ln) doesn't seem to care, but BlockRead gives me an error 32.

Aren't untyped file access being read/write by default? Try to
fiddle with filemode to try to make it readonly.

[Robert Prins]

Post by Marco van de Voort

Post by Robert Prins
Does anyone know what I need to do to BlockRead a file that's currently open?
Normal Read(Ln) doesn't seem to care, but BlockRead gives me an error 32.

Aren't untyped file access being read/write by default? Try to
fiddle with filemode to try to make it readonly.

Back at this again, and setting FileMode to $40 (open_access_ReadOnly OR
open_share_DenyNone) works when I run the program in the VP IDE. From the
command line is still results in an RTE 32.

Robert