refactor: precompute constant and adjust tolerance

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---

Author: Planeshifter

lib/node_modules/@stdlib/stats/base/dists/gumbel/stdev/lib/main.js

@@ -21,13 +21,11 @@
 // MODULES //
 
 var isnan = require( '@stdlib/math/base/assert/is-nan' );
-var sqrt = require( '@stdlib/math/base/special/sqrt' );
-var PI = require( '@stdlib/constants/float64/pi' );
 
 
 // VARIABLES //
 
-var SQRT6 = sqrt( 6.0 );
+var PI_OVER_SQRT6 = 1.282549830161864; // Pi divided by the square root of 6
 
 
 // MAIN //
@@ -67,7 +65,7 @@ function stdev( mu, beta ) {
 	) {
 		return NaN;
 	}
-	return ( PI / SQRT6 ) * beta;
+	return PI_OVER_SQRT6 * beta;
 }
 
 

lib/node_modules/@stdlib/stats/base/dists/gumbel/stdev/manifest.json

@@ -39,9 +39,7 @@
       "libpath": [],
       "dependencies": [
         "@stdlib/math/base/napi/binary",
-        "@stdlib/math/base/assert/is-nan",
-        "@stdlib/math/base/special/sqrt",
-        "@stdlib/constants/float64/pi"
+        "@stdlib/math/base/assert/is-nan"
       ]
     },
     {
@@ -57,8 +55,6 @@
       "libpath": [],
       "dependencies": [
         "@stdlib/math/base/assert/is-nan",
-        "@stdlib/math/base/special/sqrt",
-        "@stdlib/constants/float64/pi",
         "@stdlib/constants/float64/eps"
       ]
     },
@@ -74,9 +70,7 @@
       "libraries": [],
       "libpath": [],
       "dependencies": [
-        "@stdlib/math/base/assert/is-nan",
-        "@stdlib/math/base/special/sqrt",
-        "@stdlib/constants/float64/pi"
+        "@stdlib/math/base/assert/is-nan"
       ]
     }
   ]

lib/node_modules/@stdlib/stats/base/dists/gumbel/stdev/src/main.c

@@ -18,8 +18,8 @@
 
 #include "stdlib/stats/base/dists/gumbel/stdev.h"
 #include "stdlib/math/base/assert/is_nan.h"
-#include "stdlib/math/base/special/sqrt.h"
-#include "stdlib/constants/float64/pi.h"
+
+static const double PI_OVER_SQRT6 = 1.282549830161864; // Pi divided by the square root of 6
 
 /**
 * Returns the standard deviation for a Gumbel distribution with location `mu` and scale `beta`.
@@ -33,14 +33,12 @@
 * // returns ~1.283
 */
 double stdlib_base_dists_gumbel_stdev( const double mu, const double beta ) {
-	double SQRT6 = stdlib_base_sqrt( 6.0 );
-
 	if (
 		stdlib_base_is_nan( mu ) ||
 		stdlib_base_is_nan( beta ) ||
 		beta <= 0.0
 	) {
 		return 0.0/0.0; // NaN
 	}
-	return ( STDLIB_CONSTANT_FLOAT64_PI / SQRT6 ) * beta;
+	return PI_OVER_SQRT6 * beta;
 }

lib/node_modules/@stdlib/stats/base/dists/gumbel/stdev/test/test.js

@@ -96,7 +96,7 @@ tape( 'the function returns the standard deviation of a Gumbel distribution', fu
 				t.equal( y, expected[i], 'mu:'+mu[i]+', beta: '+beta[i]+', y: '+y+', expected: '+expected[i] );
 			} else {
 				delta = abs( y - expected[ i ] );
-				tol = 2.0 * EPS * abs( expected[ i ] );
+				tol = 1.0 * EPS * abs( expected[ i ] );
 				t.ok( delta <= tol, 'within tolerance. mu: '+mu[i]+'. beta: '+beta[i]+'. y: '+y+'. E: '+expected[ i ]+'. Δ: '+delta+'. tol: '+tol+'.' );
 			}
 		}

lib/node_modules/@stdlib/stats/base/dists/gumbel/stdev/test/test.native.js

@@ -105,7 +105,7 @@ tape( 'the function returns the standard deviation of a Gumbel distribution', op
 				t.equal( y, expected[i], 'mu:'+mu[i]+', beta: '+beta[i]+', y: '+y+', expected: '+expected[i] );
 			} else {
 				delta = abs( y - expected[ i ] );
-				tol = 2.0 * EPS * abs( expected[ i ] );
+				tol = 1.0 * EPS * abs( expected[ i ] );
 				t.ok( delta <= tol, 'within tolerance. mu: '+mu[i]+'. beta: '+beta[i]+'. y: '+y+'. E: '+expected[ i ]+'. Δ: '+delta+'. tol: '+tol+'.' );
 			}
 		}