From 2ed52bf0d181da1d9fd165cc31ab5384771bee91 Mon Sep 17 00:00:00 2001
From: Rutger van Bergen <rbergen@xs4all.nl>
Date: Thu, 7 Nov 2024 08:22:22 +0100
Subject: [PATCH] Revert "Walk prebuilt mask through memory for small steps"

---
 PrimeCPP/solution_2/PrimeCPP_PAR.cpp | 59 +---------------------------
 1 file changed, 1 insertion(+), 58 deletions(-)

diff --git a/PrimeCPP/solution_2/PrimeCPP_PAR.cpp b/PrimeCPP/solution_2/PrimeCPP_PAR.cpp
index fe79df276..3345d6505 100644
--- a/PrimeCPP/solution_2/PrimeCPP_PAR.cpp
+++ b/PrimeCPP/solution_2/PrimeCPP_PAR.cpp
@@ -61,64 +61,7 @@ class BitArray {
         array[index(n)] |= (uint8_t(1) << (n % 8));
     }
 
-    static constexpr uint32_t buildSkipMask(size_t skip, size_t offset) 
-    {
-        uint32_t mask = 0;
-        for (size_t i = offset; i < 32; i += skip) {
-            mask |= (1u << i);
-        }
-        return ~mask;
-    }
-
-    uint32_t rol(uint32_t value, size_t bits) 
-    {
-        bits %= 32;
-        if (bits == 0) 
-            return value;
-        // Ensure that the number of bits to rotate is within 0-31
-        return (value << bits) | (value >> (32 - bits));
-    }
-
-    void setFlagsFalse(size_t n, size_t skip) 
-    {
-        if (skip <= 12) {
-            // For small skips, use pre-built mask approach
-            size_t word_idx = index(n);
-            size_t bit_pos = n % 32;
-            size_t curr_n = n;
-            
-            while (curr_n < size()) 
-            {
-                // Build mask for current word starting at bit_pos
-                uint32_t mask = buildSkipMask(skip, bit_pos);
-                
-                // Apply mask to current word
-                array[word_idx] &= mask;
-                
-                // Move to next word
-                size_t bits_remaining = 32 - bit_pos;
-                curr_n += ((bits_remaining + skip - 1) / skip) * skip;
-                
-                if (curr_n >= size()) break;
-                
-                word_idx = index(curr_n);
-                bit_pos = curr_n % 32;
-            }
-        } 
-        else 
-        {
-            // Original implementation for larger skips
-            auto rolling_mask = ~uint32_t(1 << (n % 32));
-            auto roll_bits = skip % 32;
-            while (n < size()) {
-                array[index(n)] &= rolling_mask;
-                n += skip;
-                rolling_mask = rol(rolling_mask, roll_bits);
-            }
-        }
-    }
-    
-    inline size_t size() const 
+    constexpr size_t size() const 
     {
         return logicalSize;
     }