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add specs file for radix_sort
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‎doc/specs/stdlib_sorting.md‎

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@@ -25,9 +25,9 @@ module's `string_type` type.
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## Overview of the module
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The module `stdlib_sorting` defines several public entities, one
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default integer parameter, `int_size`, and three overloaded
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subroutines: `ORD_SORT`, `SORT`, and `SORT_INDEX`. The
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overloaded subroutines also each have seven specific names for
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default integer parameter, `int_size`, and four overloaded
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subroutines: `ORD_SORT`, `SORT`, `RADIX_SORT` and `SORT_INDEX`. The
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overloaded subroutines also each have several specific names for
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versions corresponding to different types of array arguments.
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### The `int_size` parameter
@@ -47,9 +47,11 @@ data:
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* `SORT_INDEX` is based on `ORD_SORT`, but in addition to sorting the
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input array, it returns indices that map the original array to its
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sorted version. This enables related arrays to be re-ordered in the
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same way; and
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same way;
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* `SORT` is intended to sort simple arrays of intrinsic data
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that are effectively unordered before the sort.
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that are effectively unordered before the sort;
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* `RADIX_SORT` is intended to sort fixed width intrinsic data
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types (integers and reals).
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#### Licensing
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@@ -196,6 +198,18 @@ magnitude slower than `ORD_SORT`. Its memory requirements are also
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low, being of order O(Ln(N)), while the memory requirements of
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`ORD_SORT` and `SORT_INDEX` are of order O(N).
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#### The `RADIX_SORT` subroutine
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`RADIX_SORT` is a implementation of LSD [radix sort](https://en.wikipedia.org/wiki/Radix_sort),
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using `256` (one byte) as the radix. It only works for fixed width data,
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thus integers and reals. `RADIX_SORT` is always of O(N) runtime performance
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for any input data. For large and random data, it is about five (or more)
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times faster than other sort subroutines.
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The `RADIX_SORT` needs a buffer that have same size of the input data.
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Your can provide it using `work` arguement, if not the subroutine will
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allocate the buffer and deallocate before return.
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### Specifications of the `stdlib_sorting` procedures
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#### `ord_sort` - sorts an input array
@@ -318,6 +332,55 @@ element of `array` is a `NaN`. Sorting of `CHARACTER(*)` and
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{!example/sorting/example_sort.f90!}
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```
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#### `radix_sort` - sorts an input array
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##### Status
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Experimental
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##### Description
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Returns an input array with the elements sorted in order of increasing, or
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decreasing, value.
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##### Syntax
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`call [[stdlib_sorting(module):radix_sort(interface)]]( array[, work, reverse] )`
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##### Class
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Generic subroutine.
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##### Arguments
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`array` : shall be a rank one array of any of the types:
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`integer(int8)`, `integer(int16)`, `integer(int32)`, `integer(int64)`,
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`real(sp)`, `real(dp)`. It is an `intent(inout)` argument. On return its
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input elements will be sorted in order of non-decreasing value.
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`work` (optional): shall be a rank one array of the same type as
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array, and shall have at least `size(array)` elements. It is an
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`intent(inout)` argument, and its contents on return are undefined.
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`reverse` (optional): shall be a scalar of type default logical. It
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is an `intent(in)` argument. If present with a value of `.true.` then
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`array` will be sorted in order of non-increasing values in unstable
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order. Otherwise index will sort `array` in order of non-decreasing
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values in unstable order.
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##### Notes
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`SORT` implements a LSD radix sort algorithm with a `256` radix. For any
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input data it provides `O(N)` run time performance. If `array` is of
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any type `REAL` the order of its elements on return undefined if any
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element of `array` is a `NaN`.
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##### Example
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```fortran
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{!example/sorting/example_radix_sort.f90!}
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```
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#### `sort_index` - creates an array of sorting indices for an input array, while also sorting the array.
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##### Status
@@ -496,107 +559,126 @@ of size `16**3`, with characters drawn from the set "a"-"p":
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random order.
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These benchmarks have been performed on two different compilers, both
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on a MacBook Pro, featuring a 2.3 GHz Quad-Core Intel Core i5, with 8
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GB 2133 MHz LPDDR3 memory. The first compiler was GNU Fortran
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(GCC) 10.2.0, with the following results:
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on WSL with Ubuntu-20.04, Intel(R) Core(TM) i7-10700 CPU @ 2.9GHz, with
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32 GB DDR4 memory. The first compiler is GNU Fortran (GCC) 9.4.0, with
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the following results.
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| Type | Elements | Array Name | Method | Time (s) |
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|-------------|----------|-----------------|-------------|-----------|
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| Integer | 65536 | Blocks | Ord_Sort | 0.000579 |
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| Integer | 65536 | Decreasing | Ord_Sort | 0.000212 |
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| Integer | 65536 | Identical | Ord_Sort | 0.000165 |
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| Integer | 65536 | Increasing | Ord_Sort | 0.000131 |
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| Integer | 65536 | Random dense | Ord_Sort | 0.009991 |
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| Integer | 65536 | Random order | Ord_Sort | 0.008574 |
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| Integer | 65536 | Random sparse | Ord_Sort | 0.010504 |
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| Integer | 65536 | Random 3 | Ord_Sort | 0.000532 |
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| Integer | 65536 | Random 10 | Ord_Sort | 0.000315 |
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| Character | 65536 | Char. Decrease | Ord_Sort | 0.001041 |
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| Character | 65536 | Char. Increase | Ord_Sort | 0.000584 |
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| Character | 65536 | Char. Random | Ord_Sort | 0.026273 |
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| String_type | 4096 | String Decrease | Ord_Sort | 0.001202 |
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| String_type | 4096 | String Increase | Ord_Sort | 0.000758 |
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| String_type | 4096 | String Random | Ord_Sort | 0.018180 |
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| Integer | 65536 | Blocks | Sort | 0.005073 |
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| Integer | 65536 | Decreasing | Sort | 0.005830 |
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| Integer | 65536 | Identical | Sort | 0.007372 |
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| Integer | 65536 | Increasing | Sort | 0.002421 |
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| Integer | 65536 | Random dense | Sort | 0.007006 |
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| Integer | 65536 | Random order | Sort | 0.007211 |
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| Integer | 65536 | Random sparse | Sort | 0.007109 |
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| Integer | 65536 | Random 3 | Sort | 0.012232 |
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| Integer | 65536 | Random 10 | Sort | 0.017345 |
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| Character | 65536 | Char. Decrease | Sort | 0.031350 |
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| Character | 65536 | Char. Increase | Sort | 0.011606 |
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| Character | 65536 | Char. Random | Sort | 0.022440 |
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| String_type | 4096 | String Decrease | Sort | 0.026539 |
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| String_type | 4096 | String Increase | Sort | 0.009755 |
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| String_type | 4096 | String Random | Sort | 0.016218 |
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| Integer | 65536 | Blocks | Sort_Index | 0.000953 |
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| Integer | 65536 | Decreasing | Sort_Index | 0.000418 |
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| Integer | 65536 | Identical | Sort_Index | 0.000264 |
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| Integer | 65536 | Increasing | Sort_Index | 0.000262 |
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| Integer | 65536 | Random dense | Sort_Index | 0.009563 |
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| Integer | 65536 | Random order | Sort_Index | 0.009592 |
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| Integer | 65536 | Random sparse | Sort_Index | 0.009691 |
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| Integer | 65536 | Random 3 | Sort_Index | 0.000781 |
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| Integer | 65536 | Random 10 | Sort_Index | 0.000455 |
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| Character | 65536 | Char. Decrease | Sort_Index | 0.001189 |
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| Character | 65536 | Char. Increase | Sort_Index | 0.000752 |
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| Character | 65536 | Char. Random | Sort_Index | 0.025767 |
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| String_type | 4096 | String Decrease | Sort_Index | 0.001411 |
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| String_type | 4096 | String Increase | Sort_Index | 0.000761 |
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| String_type | 4096 | String Random | Sort_Index | 0.018202 |
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The second compiler was Intel(R) Fortran Intel(R) 64 Compiler Classic
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for applications running on Intel(R) 64, Version 2021.2.0 Build
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20210228_000000, with the following results:
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| Integer | 65536 | Blocks | Ord_Sort | 0.001048 |
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| Integer | 65536 | Decreasing | Ord_Sort | 0.000204 |
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| Integer | 65536 | Identical | Ord_Sort | 0.000097 |
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| Integer | 65536 | Increasing | Ord_Sort | 0.000096 |
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| Integer | 65536 | Random dense | Ord_Sort | 0.006580 |
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| Integer | 65536 | Random order | Ord_Sort | 0.006886 |
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| Integer | 65536 | Random sparse | Ord_Sort | 0.006821 |
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| Integer | 65536 | Random 3 | Ord_Sort | 0.000461 |
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| Integer | 65536 | Random 10 | Ord_Sort | 0.000226 |
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| Character | 65536 | Char. Decrease | Ord_Sort | 0.000824 |
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| Character | 65536 | Char. Increase | Ord_Sort | 0.000370 |
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| Character | 65536 | Char. Random | Ord_Sort | 0.016020 |
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| String_type | 4096 | String Decrease | Ord_Sort | 0.000465 |
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| String_type | 4096 | String Increase | Ord_Sort | 0.000169 |
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| String_type | 4096 | String Random | Ord_Sort | 0.004194 |
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| Integer | 65536 | Blocks | Radix_Sort | 0.001610 |
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| Integer | 65536 | Decreasing | Radix_Sort | 0.001076 |
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| Integer | 65536 | Identical | Radix_Sort | 0.001074 |
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| Integer | 65536 | Increasing | Radix_Sort | 0.001060 |
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| Integer | 65536 | Random dense | Radix_Sort | 0.001161 |
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| Integer | 65536 | Random order | Radix_Sort | 0.001069 |
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| Integer | 65536 | Random sparse | Radix_Sort | 0.001005 |
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| Integer | 65536 | Random 3 | Radix_Sort | 0.001057 |
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| Integer | 65536 | Random 10 | Radix_Sort | 0.001046 |
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| Integer | 65536 | rand-real32 | Radix_Sort | 0.001429 |
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| Integer | 65536 | Blocks | Sort | 0.004269 |
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| Integer | 65536 | Decreasing | Sort | 0.005108 |
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| Integer | 65536 | Identical | Sort | 0.006257 |
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| Integer | 65536 | Increasing | Sort | 0.002093 |
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| Integer | 65536 | Random dense | Sort | 0.006032 |
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| Integer | 65536 | Random order | Sort | 0.006030 |
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| Integer | 65536 | Random sparse | Sort | 0.006126 |
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| Integer | 65536 | Random 3 | Sort | 0.007930 |
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| Integer | 65536 | Random 10 | Sort | 0.014729 |
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| Character | 65536 | Char. Decrease | Sort | 0.020623 |
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| Character | 65536 | Char. Increase | Sort | 0.008028 |
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| Character | 65536 | Char. Random | Sort | 0.014258 |
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| String_type | 4096 | String Decrease | Sort | 0.005542 |
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| String_type | 4096 | String Increase | Sort | 0.001987 |
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| String_type | 4096 | String Random | Sort | 0.003267 |
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| Integer | 65536 | Blocks | Sort_Index | 0.000686 |
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| Integer | 65536 | Decreasing | Sort_Index | 0.000529 |
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| Integer | 65536 | Identical | Sort_Index | 0.000218 |
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| Integer | 65536 | Increasing | Sort_Index | 0.000214 |
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| Integer | 65536 | Random dense | Sort_Index | 0.008044 |
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| Integer | 65536 | Random order | Sort_Index | 0.008042 |
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| Integer | 65536 | Random sparse | Sort_Index | 0.008148 |
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| Integer | 65536 | Random 3 | Sort_Index | 0.000677 |
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| Integer | 65536 | Random 10 | Sort_Index | 0.000387 |
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| Character | 65536 | Char. Decrease | Sort_Index | 0.000932 |
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| Character | 65536 | Char. Increase | Sort_Index | 0.000487 |
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| Character | 65536 | Char. Random | Sort_Index | 0.017231 |
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| String_type | 4096 | String Decrease | Sort_Index | 0.000489 |
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| String_type | 4096 | String Increase | Sort_Index | 0.000183 |
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| String_type | 4096 | String Random | Sort_Index | 0.004102 |
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The second compiler is Intel(R) Fortran Intel(R) 64 Compiler Classic
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for applications running on Intel(R) 64, Version 2021.7.0 Build
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20220726_000000, with the following results:
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| Type | Elements | Array Name | Method | Time (s) |
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|-------------|----------|-----------------|-------------|-----------|
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| Integer | 65536 | Blocks | Ord_Sort | 0.000267 |
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| Integer | 65536 | Decreasing | Ord_Sort | 0.000068 |
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| Integer | 65536 | Identical | Ord_Sort | 0.000056 |
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| Integer | 65536 | Increasing | Ord_Sort | 0.000056 |
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| Integer | 65536 | Random dense | Ord_Sort | 0.004615 |
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| Integer | 65536 | Random order | Ord_Sort | 0.006325 |
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| Integer | 65536 | Random sparse | Ord_Sort | 0.004601 |
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| Integer | 65536 | Random 3 | Ord_Sort | 0.000193 |
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| Integer | 65536 | Random 10 | Ord_Sort | 0.000101 |
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| Character | 65536 | Char. Decrease | Ord_Sort | 0.001009 |
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| Character | 65536 | Char. Increase | Ord_Sort | 0.000529 |
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| Character | 65536 | Char. Random | Ord_Sort | 0.024547 |
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| String_type | 4096 | String Decrease | Ord_Sort | 0.003381 |
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| String_type | 4096 | String Increase | Ord_Sort | 0.000133 |
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| String_type | 4096 | String Random | Ord_Sort | 0.051985 |
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| Integer | 65536 | Blocks | Sort | 0.001614 |
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| Integer | 65536 | Decreasing | Sort | 0.001783 |
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| Integer | 65536 | Identical | Sort | 0.002111 |
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| Integer | 65536 | Increasing | Sort | 0.000674 |
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| Integer | 65536 | Random dense | Sort | 0.003574 |
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| Integer | 65536 | Random order | Sort | 0.003296 |
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| Integer | 65536 | Random sparse | Sort | 0.003380 |
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| Integer | 65536 | Random 3 | Sort | 0.003623 |
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| Integer | 65536 | Random 10 | Sort | 0.006839 |
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| Character | 65536 | Char. Decrease | Sort | 0.032564 |
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| Character | 65536 | Char. Increase | Sort | 0.012346 |
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| Character | 65536 | Char. Random | Sort | 0.022932 |
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| String_type | 4096 | String Decrease | Sort | 0.082140 |
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| String_type | 4096 | String Increase | Sort | 0.029591 |
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| String_type | 4096 | String Random | Sort | 0.043078 |
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| Integer | 65536 | Blocks | Sort_Index | 0.000848 |
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| Integer | 65536 | Decreasing | Sort_Index | 0.000103 |
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| Integer | 65536 | Identical | Sort_Index | 0.000102 |
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| Integer | 65536 | Increasing | Sort_Index | 0.000066 |
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| Integer | 65536 | Random dense | Sort_Index | 0.006434 |
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| Integer | 65536 | Random order | Sort_Index | 0.005941 |
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| Integer | 65536 | Random sparse | Sort_Index | 0.005957 |
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| Integer | 65536 | Random 3 | Sort_Index | 0.000326 |
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| Integer | 65536 | Random 10 | Sort_Index | 0.000175 |
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| Character | 65536 | Char. Decrease | Sort_Index | 0.001082 |
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| Character | 65536 | Char. Increase | Sort_Index | 0.000468 |
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| Character | 65536 | Char. Random | Sort_Index | 0.023100 |
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| String_type | 4096 | String Decrease | Sort_Index | 0.003292 |
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| String_type | 4096 | String Increase | Sort_Index | 0.000122 |
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| String_type | 4096 | String Random | Sort_Index | 0.049155 |
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| Integer | 65536 | Blocks | Ord_Sort | 0.000135 |
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| Integer | 65536 | Decreasing | Ord_Sort | 0.000053 |
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| Integer | 65536 | Identical | Ord_Sort | 0.000033 |
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| Integer | 65536 | Increasing | Ord_Sort | 0.000034 |
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| Integer | 65536 | Random dense | Ord_Sort | 0.003291 |
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| Integer | 65536 | Random order | Ord_Sort | 0.003546 |
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| Integer | 65536 | Random sparse | Ord_Sort | 0.003313 |
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| Integer | 65536 | Random 3 | Ord_Sort | 0.000145 |
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| Integer | 65536 | Random 10 | Ord_Sort | 0.000070 |
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| Character | 65536 | Char. Decrease | Ord_Sort | 0.000696 |
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| Character | 65536 | Char. Increase | Ord_Sort | 0.000338 |
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| Character | 65536 | Char. Random | Ord_Sort | 0.015255 |
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| String_type | 4096 | String Decrease | Ord_Sort | 0.001276 |
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| String_type | 4096 | String Increase | Ord_Sort | 0.000153 |
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| String_type | 4096 | String Random | Ord_Sort | 0.024705 |
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| Integer | 65536 | Blocks | Radix_Sort | 0.001038 |
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| Integer | 65536 | Decreasing | Radix_Sort | 0.000910 |
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| Integer | 65536 | Identical | Radix_Sort | 0.000441 |
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| Integer | 65536 | Increasing | Radix_Sort | 0.000803 |
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| Integer | 65536 | Random dense | Radix_Sort | 0.000363 |
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| Integer | 65536 | Random order | Radix_Sort | 0.000741 |
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| Integer | 65536 | Random sparse | Radix_Sort | 0.000384 |
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| Integer | 65536 | Random 3 | Radix_Sort | 0.000877 |
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| Integer | 65536 | Random 10 | Radix_Sort | 0.000801 |
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| Integer | 65536 | rand-real32 | Radix_Sort | 0.000604 |
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| Integer | 65536 | Blocks | Sort | 0.001342 |
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| Integer | 65536 | Decreasing | Sort | 0.001391 |
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| Integer | 65536 | Identical | Sort | 0.001485 |
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| Integer | 65536 | Increasing | Sort | 0.000447 |
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| Integer | 65536 | Random dense | Sort | 0.002778 |
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| Integer | 65536 | Random order | Sort | 0.002896 |
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| Integer | 65536 | Random sparse | Sort | 0.003136 |
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| Integer | 65536 | Random 3 | Sort | 0.002996 |
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| Integer | 65536 | Random 10 | Sort | 0.005752 |
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| Character | 65536 | Char. Decrease | Sort | 0.021973 |
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| Character | 65536 | Char. Increase | Sort | 0.008391 |
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| Character | 65536 | Char. Random | Sort | 0.015155 |
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| String_type | 4096 | String Decrease | Sort | 0.034014 |
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| String_type | 4096 | String Increase | Sort | 0.010464 |
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| String_type | 4096 | String Random | Sort | 0.015748 |
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| Integer | 65536 | Blocks | Sort_Index | 0.000381 |
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| Integer | 65536 | Decreasing | Sort_Index | 0.000085 |
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| Integer | 65536 | Identical | Sort_Index | 0.000046 |
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| Integer | 65536 | Increasing | Sort_Index | 0.000046 |
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| Integer | 65536 | Random dense | Sort_Index | 0.004020 |
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| Integer | 65536 | Random order | Sort_Index | 0.004059 |
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| Integer | 65536 | Random sparse | Sort_Index | 0.004073 |
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| Integer | 65536 | Random 3 | Sort_Index | 0.000215 |
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| Integer | 65536 | Random 10 | Sort_Index | 0.000101 |
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| Character | 65536 | Char. Decrease | Sort_Index | 0.000680 |
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| Character | 65536 | Char. Increase | Sort_Index | 0.000356 |
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| Character | 65536 | Char. Random | Sort_Index | 0.016231 |
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| String_type | 4096 | String Decrease | Sort_Index | 0.001219 |
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| String_type | 4096 | String Increase | Sort_Index | 0.000125 |
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| String_type | 4096 | String Random | Sort_Index | 0.018631 |

‎src/stdlib_sorting.fypp‎

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@@ -430,6 +430,7 @@ module stdlib_sorting
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!! The generic subroutine interface implementing the LSD radix sort algorithm,
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!! see https://en.wikipedia.org/wiki/Radix_sort for more details.
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!! It is always O(N) in sorting random data, but need a O(N) buffer.
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!! ([Specification](../page/specs/stdlib_sorting.html#radix_sort-sorts-an-input-array))
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!!
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pure module subroutine int8_radix_sort(array, reverse)

‎test/sorting/test_sorting.f90‎

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@@ -38,7 +38,7 @@ module test_sorting
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string_rand(0:string_size-1)
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integer(int32) :: dummy(0:test_size-1)
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real(sp) :: real_dummy(0:test_size-1)
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real(sp) :: real_dummy(0:test_size-1)
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character(len=4) :: char_dummy(0:char_size-1)
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type(string_type) :: string_dummy(0:string_size-1)
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integer(int_size) :: index(0:max(test_size, char_size, string_size)-1)

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