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feat: add C implementation for @stdlib/stats/base/dists/bernoulli/entropy #3449

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Original file line number Diff line number Diff line change
Expand Up @@ -130,6 +130,93 @@ for ( i = 0; i < 10; i++ ) {

<!-- /.references -->

<!-- C interface documentation. -->

* * *

<section class="c">

## C APIs

<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. -->

<section class="intro">

</section>

<!-- /.intro -->

<!-- C usage documentation. -->

<section class="usage">

### Usage

```c
#include "stdlib/stats/base/dists/bernoulli/entropy.h"
```

#### stdlib_base_dists_bernoulli_entropy( p )

Returns the [entropy][entropy] of a [Bernoulli][bernoulli-distribution] distribution with success probability `p` (in [nats][nats]).

```c
double out = stdlib_base_dists_bernoulli_entropy( 0.1 );
// returns ~0.325
```

The function accepts the following arguments:

- **x**: `[in] double` minimum support
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- **a**: `[in] double` minimum support
- **b**: `[in] double` maximum support

```c
double stdlib_base_dists_bernoulli_entropy( const double p );
```
</section>

<!-- /.usage -->

<!-- C API usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->

<section class="notes">

</section>

<!-- /.notes -->

<!-- C API usage examples. -->

<section class="examples">

### Examples

```c
#include "stdlib/stats/base/dists/bernoulli/entropy.h"
#include <stdlib.h>
#include <stdio.h>
int main( void ) {
double p;
double y;
int i;

for ( i = 0; i < 25; i++ ) {
p = ( (double)rand() / (double)RAND_MAX ) ;
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y = stdlib_base_dists_bernoulli_entropy( p );
printf( "x: %lf , H(X;p): %lf\n", p , y );
}
}
```

</section>

<!-- /.examples -->

</section>

<!-- /.c -->

<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->

<section class="related">
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Original file line number Diff line number Diff line change
@@ -0,0 +1,146 @@
#/
# @license Apache-2.0
#
# Copyright (c) 2024 The Stdlib Authors.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#/

# VARIABLES #

ifndef VERBOSE
QUIET := @
else
QUIET :=
endif

# Determine the OS ([1][1], [2][2]).
#
# [1]: https://en.wikipedia.org/wiki/Uname#Examples
# [2]: http://stackoverflow.com/a/27776822/2225624
OS ?= $(shell uname)
ifneq (, $(findstring MINGW,$(OS)))
OS := WINNT
else
ifneq (, $(findstring MSYS,$(OS)))
OS := WINNT
else
ifneq (, $(findstring CYGWIN,$(OS)))
OS := WINNT
else
ifneq (, $(findstring Windows_NT,$(OS)))
OS := WINNT
endif
endif
endif
endif

# Define the program used for compiling C source files:
ifdef C_COMPILER
CC := $(C_COMPILER)
else
CC := gcc
endif

# Define the command-line options when compiling C files:
CFLAGS ?= \
-std=c99 \
-O3 \
-Wall \
-pedantic

# Determine whether to generate position independent code ([1][1], [2][2]).
#
# [1]: https://gcc.gnu.org/onlinedocs/gcc/Code-Gen-Options.html#Code-Gen-Options
# [2]: http://stackoverflow.com/questions/5311515/gcc-fpic-option
ifeq ($(OS), WINNT)
fPIC ?=
else
fPIC ?= -fPIC
endif

# List of includes (e.g., `-I /foo/bar -I /beep/boop/include`):
INCLUDE ?=

# List of source files:
SOURCE_FILES ?=

# List of libraries (e.g., `-lopenblas -lpthread`):
LIBRARIES ?=

# List of library paths (e.g., `-L /foo/bar -L /beep/boop`):
LIBPATH ?=

# List of C targets:
c_targets := benchmark.out


# RULES #

#/
# Compiles source files.
#
# @param {string} [C_COMPILER] - C compiler (e.g., `gcc`)
# @param {string} [CFLAGS] - C compiler options
# @param {(string|void)} [fPIC] - compiler flag determining whether to generate position independent code (e.g., `-fPIC`)
# @param {string} [INCLUDE] - list of includes (e.g., `-I /foo/bar -I /beep/boop/include`)
# @param {string} [SOURCE_FILES] - list of source files
# @param {string} [LIBPATH] - list of library paths (e.g., `-L /foo/bar -L /beep/boop`)
# @param {string} [LIBRARIES] - list of libraries (e.g., `-lopenblas -lpthread`)
#
# @example
# make
#
# @example
# make all
#/
all: $(c_targets)

.PHONY: all

#/
# Compiles C source files.
#
# @private
# @param {string} CC - C compiler (e.g., `gcc`)
# @param {string} CFLAGS - C compiler options
# @param {(string|void)} fPIC - compiler flag determining whether to generate position independent code (e.g., `-fPIC`)
# @param {string} INCLUDE - list of includes (e.g., `-I /foo/bar`)
# @param {string} SOURCE_FILES - list of source files
# @param {string} LIBPATH - list of library paths (e.g., `-L /foo/bar`)
# @param {string} LIBRARIES - list of libraries (e.g., `-lopenblas`)
#/
$(c_targets): %.out: %.c
$(QUIET) $(CC) $(CFLAGS) $(fPIC) $(INCLUDE) -o $@ $(SOURCE_FILES) $< $(LIBPATH) -lm $(LIBRARIES)

#/
# Runs compiled benchmarks.
#
# @example
# make run
#/
run: $(c_targets)
$(QUIET) ./$<

.PHONY: run

#/
# Removes generated files.
#
# @example
# make clean
#/
clean:
$(QUIET) -rm -f *.o *.out

.PHONY: clean
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Original file line number Diff line number Diff line change
@@ -0,0 +1,133 @@
/**
* @license Apache-2.0
*
* Copyright (c) 2024 The Stdlib Authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/

#include "stdlib/stats/base/dists/bernoulli/entropy.h"
#include <stdlib.h>
#include <stdio.h>
#include <math.h>
#include <time.h>
#include <sys/time.h>

#define NAME "bernoulli-entropy"
#define ITERATIONS 1000000
#define REPEATS 3

/**
* Prints the TAP version.
*/
static void print_version( void ) {
printf( "TAP version 13\n" );
}

/**
* Prints the TAP summary.
*
* @param total total number of tests
* @param passing total number of passing tests
*/
static void print_summary( int total, int passing ) {
printf( "#\n" );
printf( "1..%d\n", total ); // TAP plan
printf( "# total %d\n", total );
printf( "# pass %d\n", passing );
printf( "#\n" );
printf( "# ok\n" );
}

/**
* Prints benchmarks results.
*
* @param elapsed elapsed time in seconds
*/
static void print_results( double elapsed ) {
double rate = (double)ITERATIONS / elapsed;
printf( " ---\n" );
printf( " iterations: %d\n", ITERATIONS );
printf( " elapsed: %0.9f\n", elapsed );
printf( " rate: %0.9f\n", rate );
printf( " ...\n" );
}

/**
* Returns a clock time.
*
* @return clock time
*/
static double tic( void ) {
struct timeval now;
gettimeofday( &now, NULL );
return (double)now.tv_sec + (double)now.tv_usec/1.0e6;
}

/**
* Generates a random number on the interval [0,1).
*
* @return random number
*/
static double rand_double( void ) {
int r = rand();
return (double)r / ( (double)RAND_MAX + 1.0 );
}

/**
* Runs a benchmark.
*
* @return elapsed time in seconds
*/
static double benchmark( void ) {
double elapsed;
double p;
double y;
double t;
int i;

t = tic();
for ( i = 0; i < ITERATIONS; i++ ) {
p = ( (double)rand() / (double)RAND_MAX ) ;
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y = stdlib_base_dists_bernoulli_entropy( p );
if ( y != y ) {
printf( "should not return NaN\n" );
break;
}
}
elapsed = tic() - t;
if ( y != y ) {
printf( "should not return NaN\n" );
}
return elapsed;
}

/**
* Main execution sequence.
*/
int main( void ) {
double elapsed;
int i;

// Use the current time to seed the random number generator:
srand( time( NULL ) );

print_version();
for ( i = 0; i < REPEATS; i++ ) {
printf( "# c::%s\n", NAME );
elapsed = benchmark();
print_results( elapsed );
printf( "ok %d benchmark finished\n", i+1 );
}
print_summary( REPEATS, REPEATS );
}
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