Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:116075
MIME-Version: 1.0
References: <DM6PR07MB6618D41DE7680BE2BE8086DAF9DD9@DM6PR07MB6618.namprd07.prod.outlook.com>
 <CAEZPtU7oJRYxzJWu0Y_hAnuOroowve1ziL4rVr5ui4TRGtAk_g@mail.gmail.com>
In-Reply-To: <CAEZPtU7oJRYxzJWu0Y_hAnuOroowve1ziL4rVr5ui4TRGtAk_g@mail.gmail.com>
Date: Fri, 17 Sep 2021 21:18:01 +0700
Message-ID: <CAEZPtU74xKPAwuG5BHTL7xjiGUhdrPTsWd+MKpGTnezc5tyAwQ@mail.gmail.com>
To: tyson andre <tysonandre775@hotmail.com>
Cc: "internals@lists.php.net" <internals@lists.php.net>
Content-Type: text/plain; charset="UTF-8"
Subject: Re: [PHP-DEV] RFC: Add `final class Vector` to PHP
From: pierre.php@gmail.com (Pierre Joye)

Hi Tyson,

Back on my laptop so I will answer my question myself as I read the
source code. Please, really, that should be part of the RFC content.
Half of the questions here are about APIs, goals, etc. RFC should be
specifications as much as possible.

On Fri, Sep 17, 2021 at 12:43 PM Pierre Joye <pierre.php@gmail.com> wrote:
>
> Hello Tyson,
>
> Vector support would be very good. JIT can do a lot with them if we
> have a clean Vector implementation, or even without JIT.

Teds\Vector is named as Vector however I am afraid it is not, it is a
fixed array implementation. A vector, as in all other languages are,
for the definition, , fixed or variable sizes, of element of the same
type, The same type is absolutely key here.The reason to require the
same type is the core principle of vector (and vectorization),
structure of arrays rather than array of structs. The latter are hard
(or pointless) to parallelize and hard to optimize. An easy way to
play with Vector would be to try out numpy's Vector, which is by far
one of the best (and fastest) scripting language implementations of
Vector.

I did not spend enough time on the code, but I would by deconstructing:

typedef struct _teds_vector_entries {
size_t size;
size_t capacity;
zval *entries;
} teds_vector_entries;

to  different types (or using multiple entries with a zval_type entry.
ie. for a zval float Vector:

typedef struct _teds_vector_entries {
size_t size;
size_t capacity;
double float;
} teds_vector_entries;

Alternatively, common C port of C++ Vector do something along this line:

typedef struct _cVector{
unsigned int size;
unsigned int cnt_elements;
unsigned int element_size;
void *elements;
} cVector;

where the initialization is:

void cVectorInit (cVector *array, unsigned int element_size); where
element_size is sizeof(double) f.e.

so any append, truncate, etc. are aware of the size to be
(re)allocated, if needed.

The only addition to handle zval would be:

typedef struct _cVector{
unsigned int size;
unsigned int cnt_elements;
zval_enum type zval_type;
unsigned int element_size;
void *elements;
} cVector;

Doing so will drastically help to finally have a simple, by usage and
implementation/api, way to implement vectorization using PHP.

I would also like to suggest having it in the engine somehow, if it is
not possible to have JIT jump in here if it is not an actual type in
the engine. While it is possible to have intrinsics implementations in
any extension, it won't be as good or efficient as an engine type with
JIT support.

Also, as it stands, I do not think it can be called a Vector. So I am
not too keen for it as I don't think we need another SplFixed*Array
implementation, as simple as it could be. The RFC needs some work
anyway before any vote can be taken.

In any case, if the above would be something you may consider (to
implement an actual vector), I can help and would be happy too if you
need/like to.

Best,
-- 
Pierre

@pierrejoye | http://www.libgd.org