commit aca99a3386c8fc65a1a965cd04f9972b18491659
parent 75689c506d93f943b1a89a55334c39233256d3ae
Author: NunoSempere <nuno.sempere@protonmail.com>
Date: Sun, 16 Jul 2023 12:26:55 +0200
added better error messages!
Diffstat:
1 file changed, 43 insertions(+), 38 deletions(-)
diff --git a/scratchpad/scratchpad.c b/scratchpad/scratchpad.c
@@ -1,24 +1,19 @@
-#include <float.h> // FLT_MAX, FLT_MIN
#include <limits.h> // INT_MAX
-#include <math.h>
#include <stdint.h>
-#include <stdio.h>
#include <stdlib.h>
-#define VERBOSE 1
+#include <float.h> // FLT_MAX, FLT_MIN
+#include <stdio.h>
+#include <math.h> // erf, sqrt
+
+#define EXIT_ON_ERROR 0
// Errors
-// https://mccue.dev/pages/7-27-22-c-errors
-// Huh, first time I've really needed a struct
-// https://en.wikipedia.org/wiki/Struct_(C_programming_language)
-// https://www.cs.yale.edu/homes/aspnes/pinewiki/C(2f)Structs.html
-// https://stackoverflow.com/questions/9653072/return-a-struct-from-a-function-in-c
-// options:
-// - exit
-// - pass structs
-// to do: reuse more informative printing from build-your-own-lisp?
+// [ ] to do: reuse more informative printing from build-your-own-lisp?
+// Another option could be to exit on error. Maybe let the user decide?
struct box {
int empty;
float content;
+ char * error_msg;
};
// Example cdf
@@ -48,23 +43,23 @@ float cdf_normal_0_1(float x)
{
float mean = 0;
float std = 1;
- return 0.5 * (1 + erf((x - mean) / (std * sqrt(2))));
+ return 0.5 * (1 + erf((x - mean) / (std * sqrt(2)))); // erf from math.h
}
// Inverse cdf
struct box inverse_cdf(float cdf(float), float p)
{
// given a cdf: [-Inf, Inf] => [0,1]
- // returns x such that cdf(x) = p
- // [x] to do: add bounds, add error checking
- // [x] maybe return a struct or smth.
+ // returns a box with either
+ // x such that cdf(x) = p
+ // or an error
+ // if EXIT_ON_ERROR is set to 1, it exits instead of providing an error
struct box result;
float low = -1.0;
float high = 1.0;
// 1. Make sure that cdf(low) < p < cdf(high)
- // [x] to do: do smth with float min and float max?
int interval_found = 0;
while ((!interval_found) && (low > -FLT_MAX / 4) && (high < FLT_MAX / 4)) {
// ^ Using FLT_MIN and FLT_MAX is overkill
@@ -80,17 +75,18 @@ struct box inverse_cdf(float cdf(float), float p)
high = high * 2;
}
}
- if (0) {
- printf("FLT_MIN = %f, FLT_MAX = %f, INT_MAX = %d\n", -FLT_MAX, FLT_MAX, INT_MAX);
- printf("low: %f, high: %f\n", low, high);
- printf("interval_found? %d\n", interval_found);
- int while_condition = (!interval_found) && (low > FLT_MIN / 4) && (high < FLT_MAX / 4);
- printf("while condition: %i\n", while_condition);
- }
- if (!interval_found) {
- result.empty = 1;
- return result;
+ if (!interval_found) {
+ if(EXIT_ON_ERROR){
+ printf("Interval containing the target value not found, in function inverse_cdf, in %s (%d)", __FILE__, __LINE__);
+ exit(1);
+ }else{
+ char error_msg[200];
+ snprintf(error_msg, 200, "Interval containing the target value not found in function inverse_cdf, in %s (%d)", __FILE__, __LINE__);
+ result.empty = 1;
+ result.error_msg = error_msg;
+ return result;
+ }
} else {
int convergence_condition = 0;
@@ -123,8 +119,18 @@ struct box inverse_cdf(float cdf(float), float p)
result.content = low;
result.empty = 0;
} else {
- result.empty = 1;
- }
+ if(EXIT_ON_ERROR){
+ printf("Search process did not converge, in function inverse_cdf, in %s (%d)", __FILE__, __LINE__);
+ exit(1);
+ }else{
+ char error_msg[200];
+ snprintf(error_msg, 200, "Search process did not converge, in function inverse_cdf, in %s (%d)", __FILE__, __LINE__);
+ result.empty = 1;
+ result.error_msg = error_msg;
+ return result;
+ }
+ result.empty = 1;
+ }
return result;
}
@@ -146,13 +152,12 @@ uint32_t xorshift32(uint32_t* seed)
}
// Distribution & sampling functions
-
float rand_0_to_1(uint32_t* seed)
{
return ((float)xorshift32(seed)) / ((float)UINT32_MAX);
}
-// sampler based on inverse cdf
+// Sampler based on inverse cdf
struct box sampler(float cdf(float), uint32_t* seed)
{
struct box result;
@@ -161,16 +166,15 @@ struct box sampler(float cdf(float), uint32_t* seed)
return result;
}
-// ~~[-] to-do: integrals => beta distribution~~
-// => instead, use this incomplete beta function implementation, based on continuous fractions:
+// to do: add beta.
+// for the cdf, use this incomplete beta function implementation, based on continuous fractions:
// <https://codeplea.com/incomplete-beta-function-c>
// <https://github.com/codeplea/incbeta>
-// main with an example
int main()
{
- // Uniform:
+ // Get the inverse cdf of a [0,1] uniform distribution at 0.5
struct box result_1 = inverse_cdf(cdf_uniform_0_1, 0.5);
char* name_1 = "cdf_uniform_0_1";
if (result_1.empty) {
@@ -180,7 +184,7 @@ int main()
printf("Inverse of %s at %f is: %f\n", name_1, 0.5, result_1.content);
}
- // Squared cdf
+ // Get the inverse cdf of a [0,1] squared distribution at 0.5
struct box result_2 = inverse_cdf(cdf_squared_0_1, 0.5);
char* name_2 = "cdf_squared_0_1";
if (result_2.empty) {
@@ -190,7 +194,7 @@ int main()
printf("Inverse of %s at %f is: %f\n", name_2, 0.5, result_2.content);
}
- // Normal cdf
+ // Get the inverse of a normal(0,1) cdf distribution
struct box result_3 = inverse_cdf(cdf_normal_0_1, 0.5);
char* name_3 = "cdf_normal_0_1";
if (result_3.empty) {
@@ -200,6 +204,7 @@ int main()
printf("Inverse of %s at %f is: %f\n", name_3, 0.5, result_3.content);
}
+ // Use the sampler on a normal(0,1)
// set randomness seed
uint32_t* seed = malloc(sizeof(uint32_t));
*seed = 1000; // xorshift can't start with 0
