mirror of
https://github.com/TREX-CoE/qmckl.git
synced 2024-11-19 12:32:40 +01:00
334 lines
9.3 KiB
Org Mode
334 lines
9.3 KiB
Org Mode
#+TITLE: Numerical precision
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#+SETUPFILE: ../tools/theme.setup
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#+INCLUDE: ../tools/lib.org
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* Headers :noexport:
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#+begin_src c :tangle (eval c_test) :noweb yes
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#include "qmckl.h"
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#include "assert.h"
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#ifdef HAVE_CONFIG_H
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#include "config.h"
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#endif
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int main() {
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#+end_src
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#+begin_src c :tangle (eval h_private_type)
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#ifndef QMCKL_NUMPREC_HPT
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#define QMCKL_NUMPREC_HPT
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#ifdef HAVE_STDINT_H
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#include <stdint.h>
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#elif HAVE_INTTYPES_H
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#include <inttypes.h>
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#endif
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#+end_src
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#+begin_src c :tangle (eval c)
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#ifdef HAVE_CONFIG_H
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#include "config.h"
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#endif
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#ifdef HAVE_STDINT_H
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#include <stdint.h>
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#elif HAVE_INTTYPES_H
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#include <inttypes.h>
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#endif
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#include <assert.h>
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#include <math.h>
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#include <stdlib.h>
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#include <string.h>
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#include "qmckl.h"
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#include "qmckl_context_private_type.h"
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#+end_src
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* Control of the numerical precision
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Controlling numerical precision enables optimizations. Here, the
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default parameters determining the target numerical precision and
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range are defined. Following the IEEE Standard for Floating-Point
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Arithmetic (IEEE 754), /precision/ refers to the number of significand bits and /range/
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refers to the number of exponent bits.
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#+NAME: table-precision
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| ~QMCKL_DEFAULT_PRECISION~ | 53 |
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| ~QMCKL_DEFAULT_RANGE~ | 11 |
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# We need to force Emacs not to indent the Python code:
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# -*- org-src-preserve-indentation: t
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#+begin_src python :var table=table-precision :results drawer :exports results
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""" This script generates the C and Fortran constants from the org-mode table.
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"""
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result = [ "#+begin_src c :comments org :tangle (eval h_type)" ]
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for (text, code) in table:
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text=text.replace("~","")
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result += [ f"#define {text:30s} {code:d}" ]
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result += [ "#+end_src" ]
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result += [ "" ]
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result += [ "#+begin_src f90 :comments org :tangle (eval fh_func) :exports none" ]
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for (text, code) in table:
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text=text.replace("~","")
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result += [ f" integer, parameter :: {text:30s} = {code:d}" ]
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result += [ "#+end_src" ]
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return '\n'.join(result)
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#+end_src
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#+RESULTS:
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:results:
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#+begin_src c :comments org :tangle (eval h_type)
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#define QMCKL_DEFAULT_PRECISION 53
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#define QMCKL_DEFAULT_RANGE 11
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#+end_src
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#+begin_src f90 :comments org :tangle (eval fh_func) :exports none
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integer, parameter :: QMCKL_DEFAULT_PRECISION = 53
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integer, parameter :: QMCKL_DEFAULT_RANGE = 11
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#+end_src
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:end:
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#+begin_src c :comments org :tangle (eval h_private_type)
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typedef struct qmckl_numprec_struct {
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uint32_t precision;
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uint32_t range;
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} qmckl_numprec_struct;
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#+end_src
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The following functions set and get the required precision and
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range. ~precision~ is an integer between 2 and 53, and ~range~ is an
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integer between 2 and 11.
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The setter functions functions return a new context as a 64-bit
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integer. The getter functions return the value, as a 32-bit
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integer. The update functions return ~QMCKL_SUCCESS~ or ~QMCKL_FAILURE~.
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* Precision ~qmckl_context_set_numprec_precision~ modifies the parameter for the
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numerical precision in the context.
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# Header
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#+begin_src c :comments org :tangle (eval h_func) :exports none
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qmckl_exit_code qmckl_set_numprec_precision(const qmckl_context context, const int precision);
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#+end_src
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# Source
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#+begin_src c :tangle (eval c)
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qmckl_exit_code qmckl_set_numprec_precision(const qmckl_context context, const int precision) {
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if (qmckl_context_check(context) == QMCKL_NULL_CONTEXT)
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return QMCKL_INVALID_CONTEXT;
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if (precision < 2) {
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return qmckl_failwith(context,
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QMCKL_INVALID_ARG_2,
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"qmckl_update_numprec_precision",
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"precision < 2");
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}
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if (precision > 53) {
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return qmckl_failwith(context,
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QMCKL_INVALID_ARG_2,
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"qmckl_update_numprec_precision",
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"precision > 53");
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}
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qmckl_context_struct* const ctx = (qmckl_context_struct* const) context;
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/* This should be always true because the context is valid */
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assert (ctx != NULL);
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qmckl_lock(context);
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{
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ctx->numprec.precision = (uint32_t) precision;
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}
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qmckl_unlock(context);
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return QMCKL_SUCCESS;
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}
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#+end_src
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# Fortran interface
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#+begin_src f90 :tangle (eval fh_func)
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interface
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integer (qmckl_exit_code) function qmckl_set_numprec_precision(context, precision) bind(C)
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use, intrinsic :: iso_c_binding
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import
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integer (qmckl_context), intent(in), value :: context
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integer (c_int32_t), intent(in), value :: precision
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end function qmckl_set_numprec_precision
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end interface
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#+end_src ~qmckl_get_numprec_precision~ returns the value of the numerical precision in the context.
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#+begin_src c :comments org :tangle (eval h_func) :exports none
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int32_t qmckl_get_numprec_precision(const qmckl_context context);
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#+end_src
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# Source
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#+begin_src c :tangle (eval c)
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int qmckl_get_numprec_precision(const qmckl_context context) {
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if (qmckl_context_check(context) == QMCKL_NULL_CONTEXT) {
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return qmckl_failwith(context,
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QMCKL_INVALID_CONTEXT,
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"qmckl_get_numprec_precision",
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"");
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}
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const qmckl_context_struct* const ctx = (qmckl_context_struct* const) context;
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return ctx->numprec.precision;
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}
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#+end_src
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# Fortran interface
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#+begin_src f90 :tangle (eval fh_func)
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interface
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integer (qmckl_exit_code) function qmckl_get_numprec_precision(context) bind(C)
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use, intrinsic :: iso_c_binding
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import
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integer (qmckl_context), intent(in), value :: context
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end function qmckl_get_numprec_precision
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end interface
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#+end_src
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* Range ~qmckl_set_numprec_range~ modifies the parameter for the numerical
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range in a given context.
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# Header
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#+begin_src c :comments org :tangle (eval h_func) :exports none
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qmckl_exit_code qmckl_set_numprec_range(const qmckl_context context, const int range);
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#+end_src
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# Source
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#+begin_src c :tangle (eval c)
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qmckl_exit_code qmckl_set_numprec_range(const qmckl_context context, const int range) {
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if (qmckl_context_check(context) == QMCKL_NULL_CONTEXT)
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return QMCKL_INVALID_CONTEXT;
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if (range < 2) {
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return qmckl_failwith(context,
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QMCKL_INVALID_ARG_2,
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"qmckl_set_numprec_range",
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"range < 2");
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}
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if (range > 11) {
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return qmckl_failwith(context,
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QMCKL_INVALID_ARG_2,
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"qmckl_set_numprec_range",
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"range > 11");
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}
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qmckl_context_struct* const ctx = (qmckl_context_struct* const) context;
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/* This should be always true because the context is valid */
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assert (ctx != NULL);
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qmckl_lock(context);
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{
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ctx->numprec.range = (uint32_t) range;
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}
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qmckl_unlock(context);
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return QMCKL_SUCCESS;
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}
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#+end_src
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# Fortran interface
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#+begin_src f90 :tangle (eval fh_func)
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interface
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integer (qmckl_exit_code) function qmckl_numprec_set_range(context, range) bind(C)
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use, intrinsic :: iso_c_binding
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import
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integer (qmckl_context), intent(in), value :: context
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integer (c_int32_t), intent(in), value :: range
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end function qmckl_numprec_set_range
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end interface
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#+end_src ~qmckl_get_numprec_range~ returns the value of the numerical range in the context.
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#+begin_src c :comments org :tangle (eval h_func) :exports none
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int32_t qmckl_context_get_range(const qmckl_context context);
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#+end_src
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# Source
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#+begin_src c :tangle (eval c)
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int qmckl_get_numprec_range(const qmckl_context context) {
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if (qmckl_context_check(context) == QMCKL_NULL_CONTEXT) {
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return qmckl_failwith(context,
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QMCKL_INVALID_CONTEXT,
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"qmckl_get_numprec_range",
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"");
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}
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const qmckl_context_struct* const ctx = (qmckl_context_struct* const) context;
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return ctx->numprec.range;
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}
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#+end_src
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# Fortran interface
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#+begin_src f90 :tangle (eval fh_func) :exports none
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interface
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integer (qmckl_exit_code) function qmckl_get_numprec_range(context) bind(C)
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use, intrinsic :: iso_c_binding
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import
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integer (qmckl_context), intent(in), value :: context
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end function qmckl_get_numprec_range
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end interface
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#+end_src
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* Helper functions ~qmckl_get_numprec_epsilon~ returns $\epsilon = 2^{1-n}$ where ~n~ is the precision.
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We need to remove the sign bit from the precision.
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#+begin_src c :comments org :tangle (eval h_func) :exports none
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double qmckl_get_numprec_epsilon(const qmckl_context context);
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#+end_src
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# Source
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#+begin_src c :tangle (eval c)
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double qmckl_get_numprec_epsilon(const qmckl_context context) {
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const int precision = qmckl_get_numprec_precision(context);
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return 1. / (double) (1L << (precision-2));
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}
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#+end_src
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# Fortran interface
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#+begin_src f90 :tangle (eval fh_func) :exports none
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interface
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real (c_double) function qmckl_get_numprec_epsilon(context) bind(C)
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use, intrinsic :: iso_c_binding
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import
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integer (qmckl_context), intent(in), value :: context
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end function qmckl_get_numprec_epsilon
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end interface
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#+end_src
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* End of files :noexport:
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#+begin_src c :comments link :tangle (eval h_private_type)
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#endif
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#+end_src
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*** Test
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#+begin_src c :comments link :tangle (eval c_test)
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return 0;
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}
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#+end_src
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