#+TITLE: Context
#+SETUPFILE: ../docs/theme.setup
#+INCLUDE: ../tools/lib.org                                                                  

* Headers                                                          :noexport:

  #+begin_src c :tangle (eval c_test) :noweb yes
#include "qmckl.h"
#include "munit.h"
MunitResult test_<<filename()>>() {
  #+end_src

  #+begin_src c :tangle (eval h_private_type) :noweb yes
#ifndef QMCKL_CONTEXT_HPT
#define QMCKL_CONTEXT_HPT

#include <stdint.h>
#include <pthread.h>

#include "qmckl_error_private_type.h"
#include "qmckl_memory_private_type.h"
#include "qmckl_numprec_private_type.h"
#include "qmckl_electron_private_type.h"
#include "qmckl_ao_private_type.h"
  #+end_src

  #+begin_src c :tangle (eval c) 
#include <stdint.h>
#include <assert.h>
#include <math.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>

#include "qmckl_error_type.h"
#include "qmckl_context_private_type.h"
#include "qmckl_context_type.h"
#include "qmckl_numprec_type.h"

#include "qmckl_memory_private_func.h"
#include "qmckl_context_func.h"

  #+end_src

* Context handling

  The context variable is a handle for the state of the library,
  and is stored in a data structure which can't be seen outside of
  the library. To simplify compatibility with other languages, the
  pointer to the internal data structure is converted into a 64-bit
  signed integer, defined in the ~qmckl_context~ type.
  A value of ~QMCKL_NULL_CONTEXT~ for the context is equivalent to a
  ~NULL~ pointer.

  #+NAME: qmckl_context
  #+begin_src c :comments org :tangle (eval h_type)
typedef int64_t qmckl_context ;
#define QMCKL_NULL_CONTEXT (qmckl_context) 0
  #+end_src

  #+begin_src f90 :comments org :tangle (eval fh_type) :exports none
      integer  , parameter :: qmckl_context = c_int64_t
      integer*8, parameter :: QMCKL_NULL_CONTEXT = 0
  #+end_src
   
  An immutable context would have required to implement a garbage
  collector. To keep the library simple, we have chosen to implement
  the context as a mutable data structure, so it has to be handled
  with care.

  By convention, in this file ~context~ is a ~qmckl_context~ variable
  and ~ctx~ is a ~qmckl_context_struct*~ pointer.

** Data structure
   
   #+begin_src c :comments org :tangle (eval h_private_type) :noweb yes :exports none
typedef struct qmckl_context_struct {
  /* -- State of the library -- */

  /* Validity checking */
  uint64_t                 tag;

  /* Numerical precision */
  qmckl_numprec_struct     numprec;

  /* Thread lock */
  int                      lock_count;
  pthread_mutex_t          mutex;

  /* Error handling */
  qmckl_error_struct       error;

  /* Memory allocation */
  qmckl_memory_struct      memory;

  /* Current date */
  uint64_t                 date;

  /* -- Molecular system -- */
  qmckl_electron_struct    electron;
  qmckl_ao_basis_struct    ao_basis;

  /* To be implemented:
  qmckl_nucleus_struct     nucleus;
  qmckl_mo_struct          mo;
  qmckl_determinant_struct det;
  ,*/

} qmckl_context_struct;
   #+end_src

   The context keeps a ``date'' that allows to check which data needs
   to be recomputed. The date is incremented when the electron
   coordinates are updated.
   
   When a new element is added to the context, the functions
   [[Creation][qmckl_context_create]], [[Destroy][qmckl_context_destroy]] and [[Copy][qmckl_context_copy]]
   should be updated inorder to make deep copies.
   

   A tag is used internally to check if the memory domain pointed
   by a pointer is a valid context. This allows to check that even if
   the pointer associated with a context is non-null, we can still
   verify that it points to the expected data structure.

   #+begin_src c :comments org :tangle (eval h_private_type) :noweb yes
#define VALID_TAG   0xBEEFFACE
#define INVALID_TAG 0xDEADBEEF
   #+end_src

   The ~qmckl_context_check~ function checks if the domain pointed by
   the pointer is a valid context. It returns the input ~qmckl_context~
   if the context is valid, ~QMCKL_NULL_CONTEXT~ otherwise.

   #+begin_src c :comments org :tangle (eval h_func) :noexport
qmckl_context qmckl_context_check(const qmckl_context context) ;
   #+end_src

   #+begin_src c :tangle (eval c)
qmckl_context qmckl_context_check(const qmckl_context context) {

  if (context == QMCKL_NULL_CONTEXT)
    return QMCKL_NULL_CONTEXT;

  const qmckl_context_struct* const ctx = (const qmckl_context_struct* const) context;

  /* Try to access memory */
  if (ctx->tag != VALID_TAG) {
      return QMCKL_NULL_CONTEXT;
  }

  return context;
}
   #+end_src

** Creation
   
   To create a new context, ~qmckl_context_create()~ should be used.
   - Upon success, it returns a pointer to a new context with the ~qmckl_context~ type
   - It returns ~QMCKL_NULL_CONTEXT~ upon failure to allocate the internal data structure

   # Header
   #+begin_src c :comments org :tangle (eval h_func) :exports none
qmckl_context qmckl_context_create();
   #+end_src

   # Source
   #+begin_src c :tangle (eval c)
qmckl_context qmckl_context_create() {

  qmckl_context_struct* const ctx =
    (qmckl_context_struct* const) malloc (sizeof(qmckl_context_struct));

  if (ctx == NULL) {
    return QMCKL_NULL_CONTEXT;
  }

  /* Set all pointers and values to NULL */
  {
    memset(ctx, 0, sizeof(qmckl_context_struct));
  }

  /* Initialize lock */
  {
    pthread_mutexattr_t attr;
    int rc;
    
    rc = pthread_mutexattr_init(&attr); 
    assert (rc == 0);
    
    (void) pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE);
    
    rc = pthread_mutex_init ( &(ctx->mutex), &attr);
    assert (rc == 0);
    
    (void) pthread_mutexattr_destroy(&attr);
  }  

  /* Initialize data */
  ctx->tag = VALID_TAG;

  const qmckl_context context = (const qmckl_context) ctx;
  assert ( qmckl_context_check(context) != QMCKL_NULL_CONTEXT );

  ctx->numprec.precision = QMCKL_DEFAULT_PRECISION;
  ctx->numprec.range = QMCKL_DEFAULT_RANGE;

  ctx->ao_basis.uninitialized = (1 << 10) - 1;
  ctx->electron.uninitialized = (1 << 2) - 1;

  /* Allocate qmckl_memory_struct */
  {
    const size_t size = 128L;
    qmckl_memory_info_struct * new_array = calloc(size, sizeof(qmckl_memory_info_struct));
    if (new_array == NULL) {
      free(ctx);
      return QMCKL_NULL_CONTEXT; 
    }
    memset( &(new_array[0]), 0, size * sizeof(qmckl_memory_info_struct) );
    
    ctx->memory.element = new_array;
    ctx->memory.array_size = size;
    ctx->memory.n_allocated = (size_t) 0;
  }
  
  return (qmckl_context) ctx;
}
   #+end_src

   # Fortran interface
   #+begin_src f90 :tangle (eval fh_func) :exports none
  interface
     integer (qmckl_context) function qmckl_context_create() bind(C)
       use, intrinsic :: iso_c_binding
       import
     end function qmckl_context_create
  end interface
   #+end_src

   # Test
   #+begin_src c :comments link :tangle (eval c_test) :exports none
munit_assert_int64( qmckl_context_check(QMCKL_NULL_CONTEXT), ==,  QMCKL_NULL_CONTEXT);

qmckl_context context = qmckl_context_create();
munit_assert_int64( context, !=, QMCKL_NULL_CONTEXT );
munit_assert_int64( qmckl_context_check(context), ==,  context );
   #+end_src

** Locking

   For thread safety, the context may be locked/unlocked. The lock is
   initialized with the ~PTHREAD_MUTEX_RECURSIVE~ attribute, and the
   number of times the thread has locked it is saved in the
   ~lock_count~ attribute.

   # Header
   #+begin_src c :comments org :tangle (eval h_func) :exports none
void qmckl_lock  (qmckl_context context);
void qmckl_unlock(qmckl_context context);
   #+end_src

   # Source
   #+begin_src c :tangle (eval c)
void qmckl_lock(qmckl_context context) {
  if (context == QMCKL_NULL_CONTEXT)
    return ;
  qmckl_context_struct* const ctx = (qmckl_context_struct* const) context;
  errno = 0;
  int rc = pthread_mutex_lock( &(ctx->mutex) );
  if (rc != 0) {
    fprintf(stderr, "DEBUG qmckl_lock:%s\n", strerror(rc) );
    fflush(stderr);
  }
  assert (rc == 0);
  ctx->lock_count += 1;
/*
  printf("  lock : %d\n", ctx->lock_count);
,*/
}

void qmckl_unlock(const qmckl_context context) {
  qmckl_context_struct* const ctx = (qmckl_context_struct* const) context;
  int rc = pthread_mutex_unlock( &(ctx->mutex) );
  if (rc != 0) {
    fprintf(stderr, "DEBUG qmckl_unlock:%s\n", strerror(rc) );
    fflush(stderr);
  }
  assert (rc == 0);
  ctx->lock_count -= 1;
/*
  printf("unlock : %d\n", ctx->lock_count);
,*/
}
   #+end_src

** TODO Copy

   ~qmckl_context_copy~ makes a deep copy of a context. It returns
   ~QMCKL_NULL_CONTEXT~ upon failure.

   # Header
   #+begin_src c :comments org :tangle (eval h_func) :exports none
qmckl_context qmckl_context_copy(const qmckl_context context);
   #+end_src

   
   # Source
   #+begin_src c :tangle (eval c)
qmckl_context qmckl_context_copy(const qmckl_context context) {

  const qmckl_context checked_context = qmckl_context_check(context);

  if (checked_context == QMCKL_NULL_CONTEXT) {
    return QMCKL_NULL_CONTEXT;
  }

  /*
  qmckl_lock(context);
  {
    
    const qmckl_context_struct* const old_ctx =
      (qmckl_context_struct* const) checked_context;
    
    qmckl_context_struct* const new_ctx =
      (qmckl_context_struct* const) malloc (context, sizeof(qmckl_context_struct));
    
    if (new_ctx == NULL) {
      qmckl_unlock(context);
      return QMCKL_NULL_CONTEXT;
    }
    
     * Copy the old context on the new one * 
     * TODO Deep copies should be done here * 
    memcpy(new_ctx, old_ctx, sizeof(qmckl_context_struct));
    
    qmckl_unlock( (qmckl_context) new_ctx );
    
    return (qmckl_context) new_ctx;
  }
  qmckl_unlock(context);
*/
    return QMCKL_NULL_CONTEXT;
}

   #+end_src

   # Fortran interface
   #+begin_src f90 :tangle (eval fh_func) :exports none
  interface
     integer (qmckl_context) function qmckl_context_copy(context) bind(C)
       use, intrinsic :: iso_c_binding
       import
       integer (qmckl_context), intent(in), value :: context
     end function qmckl_context_copy
  end interface
   #+end_src

   # Test
   #+begin_src c :comments link :tangle (eval c_test) :exports none
/*
qmckl_context new_context = qmckl_context_copy(context);
munit_assert_int64(new_context, !=, QMCKL_NULL_CONTEXT);
munit_assert_int64(new_context, !=, context);
munit_assert_int64(qmckl_context_check(new_context), ==, new_context);
*/
   #+end_src

** Destroy

   The context is destroyed with ~qmckl_context_destroy~, leaving the ancestors untouched.
   It frees the context, and returns the previous context.

   # Header
   #+begin_src c :comments org :tangle (eval h_func) :exports none
qmckl_exit_code qmckl_context_destroy(const qmckl_context context);
   #+end_src

    # Source
    #+begin_src c :tangle (eval c)
qmckl_exit_code qmckl_context_destroy(const qmckl_context context) {

  const qmckl_context checked_context = qmckl_context_check(context);
  if (checked_context == QMCKL_NULL_CONTEXT) return QMCKL_INVALID_CONTEXT;

  qmckl_context_struct* const ctx = (qmckl_context_struct* const) context;
  assert (ctx != NULL);  /* Shouldn't be possible because the context is valid */

  qmckl_lock(context);
  {
    /* Memory: Remove all allocated data */
    for (size_t pos = (size_t) 0 ; pos < ctx->memory.array_size ; ++pos) {
      if (ctx->memory.element[pos].pointer != NULL) {
        free(ctx->memory.element[pos].pointer);
        memset( &(ctx->memory.element[pos]), 0, sizeof(qmckl_memory_info_struct) );
        ctx->memory.n_allocated -= 1;
      }
    }
    assert (ctx->memory.n_allocated == (size_t) 0);
    free(ctx->memory.element);
    ctx->memory.element = NULL;
    ctx->memory.array_size = (size_t) 0;
  }
  qmckl_unlock(context);

  ctx->tag = INVALID_TAG;

  const int rc_destroy = pthread_mutex_destroy( &(ctx->mutex) );
  if (rc_destroy != 0) {
/* DEBUG */
     fprintf(stderr, "qmckl_context_destroy: %s (count = %d)\n", strerror(rc_destroy), ctx->lock_count);
     abort();
  }

  free(ctx);

  return QMCKL_SUCCESS;
}
    #+end_src

    # Fortran interface
    #+begin_src f90 :tangle (eval fh_func)  :exports none
  interface
     integer (qmckl_exit_code) function qmckl_context_destroy(context) bind(C)
       use, intrinsic :: iso_c_binding
       import
       integer (qmckl_context), intent(in), value :: context
     end function qmckl_context_destroy
  end interface
    #+end_src

    # Test
    #+begin_src c :tangle (eval c_test)  :exports none
/* Destroy valid context */
munit_assert_int64(qmckl_context_check(context), ==, context);
munit_assert_int32(qmckl_context_destroy(context), ==, QMCKL_SUCCESS);

/* Check that context is destroyed  */
munit_assert_int64(qmckl_context_check(context), !=, context);
munit_assert_int64(qmckl_context_check(context), ==, QMCKL_NULL_CONTEXT);

/* Destroy invalid context */
munit_assert_int32(qmckl_context_destroy(QMCKL_NULL_CONTEXT), ==, QMCKL_INVALID_CONTEXT);
    #+end_src

* End of files                                                     :noexport:


  #+begin_src c :comments link :tangle (eval h_private_type)
#endif
  #+end_src

*** Test
     #+begin_src c :comments link :tangle (eval c_test)
return MUNIT_OK;
}
     #+end_src