⚡️ Faster Congruencial 32bits (#512)

* ⚡️ Faster Congruencial 32bits * Update LinearCongruential.ts
dubzzz · Jan 8, 2023 · b4852a8 · b4852a8
1 parent 0bde03e
commit b4852a8
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Showing 2 changed files with 5 additions and 5 deletions.
diff --git a/src/generator/LinearCongruential.ts b/src/generator/LinearCongruential.ts
@@ -16,8 +16,8 @@ const computeValueFromNextSeed = function (nextseed: number) {
 };
 
 class LinearCongruential32 implements RandomGenerator {
-  static readonly min: number = 0;
-  static readonly max: number = 0xffffffff;
+  static readonly min: number = -0x80000000;
+  static readonly max: number = 0x7fffffff;
 
   constructor(private seed: number) {}
 
@@ -52,7 +52,7 @@ class LinearCongruential32 implements RandomGenerator {
     // but as binary operations truncate between -0x80000000 and 0x7fffffff in JavaScript
     // we can get rid of this operation
     const vnext = v3 + ((v2 + (v1 << 15)) << 15);
-    return ((vnext + 0x80000000) | 0) + 0x80000000;
+    return vnext | 0;
   }
 }
 

diff --git a/test/unit/generator/LinearCongruencial.spec.ts b/test/unit/generator/LinearCongruencial.spec.ts
@@ -127,12 +127,12 @@ describe('congruential32', () => {
         100594764, 1754357691, 2940213637, 1822860290, 1822569888, 3692081352, 4126111909, 2548328615, 1559153086,
         2229736813, 3416000363, 1307522393, 2537287304, 1493158878, 3075976674, 3907402638, 433041229, 3014088443,
         3259785341, 1539470501, 1803261200, 518157909, 1135233158, 406515323, 3831259675, 2405854817, 1438184902,
-      ]
+      ].map((v) => v | 0)
     );
   });
   it('Should return the same sequence given same seeds', () => fc.assert(p.sameSeedSameSequences(congruential32)));
   it('Should return the same sequence if called twice', () => fc.assert(p.sameSequencesIfCallTwice(congruential32)));
-  it('Should generate values between 0 and 2**32 -1', () => fc.assert(p.valuesInRange(congruential32)));
+  it('Should generate values between -2**31 and 2**31 -1', () => fc.assert(p.valuesInRange(congruential32)));
   it('Should impact itself with unsafeNext', () => fc.assert(p.changeSelfWithUnsafeNext(congruential32)));
   it('Should not impact itself with next', () => fc.assert(p.noChangeSelfWithNext(congruential32)));
   it('Should not impact clones when impacting itself on unsafeNext', () =>