You probably want specializable and specialize inline pragmas. On Friday, June 17, 2016, Jyotirmoy Bhattacharya wrote:

Sorry, realized that attachments cannot be sent to the list. I have put the code on GitHub here https://github.com/jmoy/testing-specialize

On Fri, Jun 17, 2016 at 4:31 PM, Jyotirmoy Bhattacharya < jyotirmoy@jyotirmoy.net javascript:_e(%7B%7D,'cvml','jyotirmoy@jyotirmoy.net');> wrote:

...

I'm trying to write a mutable hash table library that would work both in the IO and ST monads, so I'm using the PrimMonad typeclass [see JmoyHash.hs in the attached archive].

For efficiency, I would like the functions to be specialized to the concrete monad at the call site. According to Section 9.31.9.2 of the GHC User's Guide https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/glasgow_exts...

The optimiser *also* considers each *imported* INLINABLE overloaded function, and specialises it for the different types at which it is called in M.

So I marked all the functions in my library as INLINABLE. Yet adding a SPECIALIZE pragma in Main.hs (currently commented out) for an imported function improves runtime performance by 3x, which should not be happening since, if I understand the manual right, the function should have been specialized anyway since it is marked INLINABLE.

I am writing to this list rather than filing a bug since I'm not sure if I'm reading the manual right and I have not explicitly verified that the specialization is not happening. I would greatly appreciate any help on both counts.

I'm using GHC 8.0.1 with the -O2 flag.

Marking the function as INLINE might solve the problem but that's something I don't want to do as it seems to me that specialization and not inlining is what's appropriate here.

Regards, Jyotirmoy Bhattacharya

Specialize inline is its own pragma. Read https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/glasgow_exts... On Friday, June 17, 2016, Jyotirmoy Bhattacharya wrote:

Thanks! I could not find the SPECIALIZABLE pragma in the docs. Can you please give me a pointer. As to inline, while it would work, there might be a large cost in code size, if say the `insert` function of a hash table were to be inlined everywhere it is used in a program.

Regards, Jyotirmoy

On Fri, Jun 17, 2016 at 9:15 PM, Carter Schonwald < carter.schonwald@gmail.com javascript:_e(%7B%7D,'cvml','carter.schonwald@gmail.com');> wrote:

...

You probably want specializable and specialize inline pragmas.

On Friday, June 17, 2016, Jyotirmoy Bhattacharya javascript:_e(%7B%7D,'cvml','jyotirmoy@jyotirmoy.net');> wrote:

...

Sorry, realized that attachments cannot be sent to the list. I have put the code on GitHub here https://github.com/jmoy/testing-specialize

On Fri, Jun 17, 2016 at 4:31 PM, Jyotirmoy Bhattacharya < jyotirmoy@jyotirmoy.net> wrote:

...

I'm trying to write a mutable hash table library that would work both in the IO and ST monads, so I'm using the PrimMonad typeclass [see JmoyHash.hs in the attached archive].

For efficiency, I would like the functions to be specialized to the concrete monad at the call site. According to Section 9.31.9.2 of the GHC User's Guide https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/glasgow_exts...

The optimiser *also* considers each *imported* INLINABLE overloaded function, and specialises it for the different types at which it is called in M.

So I marked all the functions in my library as INLINABLE. Yet adding a SPECIALIZE pragma in Main.hs (currently commented out) for an imported function improves runtime performance by 3x, which should not be happening since, if I understand the manual right, the function should have been specialized anyway since it is marked INLINABLE.

I am writing to this list rather than filing a bug since I'm not sure if I'm reading the manual right and I have not explicitly verified that the specialization is not happening. I would greatly appreciate any help on both counts.

I'm using GHC 8.0.1 with the -O2 flag.

Marking the function as INLINE might solve the problem but that's something I don't want to do as it seems to me that specialization and not inlining is what's appropriate here.

Regards, Jyotirmoy Bhattacharya