Speed up MySQL Update - InnoDB - c++

Question

I wouldn't think an update of 22*1000 values of type DOUBLE should take ~4 seconds. However that is what I am getting. The following is query is done 22 times. Perhaps this is actually on par? It doesn't satisfy my speed requirements then.
UPDATE [some table] SET [some column] = (CASE WHEN [column1] = i THEN [some number]
concatenated through i=1:1:1000, ending with END);
This statement takes ~4/22 seconds.
Remedies I have tried:
Lock table before update, and unlock after.
Thoughts to help(yet to try):
Reduce update into smaller update queries.
Additional Info:
Engine: InnoDB,
C++ Connector
EDIT 1
Code Excerpt:
Query ="LOCK TABLES CANS_SQL.SortingIndices WRITE;";
stmt = con->createStatement();
bool LOCKBIT = stmt->execute(Query);
delete stmt;
Query.clear();
Query = "UPDATE SortingIndices SET " + Objects.at(Typ).GetMetricNames().at(ObjMetIndex) + "_KVector = ( CASE ";
for (int k = 0; k<kvector.size()-1; k++)
{
while(true)
{
if(InsertCount<KvectorInsertPos.size())
{
if (KvectorInsertPos.at(InsertCount)==k)
{
Query += "WHEN Sort_ID = " + std::to_string(k+1+InsertCount) + " THEN " + std::to_string(KvectorInsertVal.at(InsertCount)+InsertCount) + " ";
InsertCount++;
}
else
break;
}
else
break;
}
Query += "WHEN Sort_ID = " + std::to_string(k+1+InsertCount) + " THEN " + std::to_string(kvector.at(k)+InsertCount) + " ";
}
while(true)
{
if(InsertCount<KvectorInsertPos.size())
{
if (KvectorInsertPos.at(InsertCount)==kvector.size()-1)
{
Query += "WHEN Sort_ID = " + std::to_string(kvector.size()+InsertCount) + " THEN " + std::to_string(KvectorInsertVal.at(InsertCount)+InsertCount) + " ";
InsertCount++;
}
else
break;
}
else
break;
}
Query += "WHEN Sort_ID = " + std::to_string(kvector.size()+InsertCount) + " THEN " + std::to_string(kvector.at(kvector.size()-1)+InsertCount) + " END ) ";
stmt = con->createStatement();
stmt->executeUpdate(Query);
delete stmt;
EDIT 2
Example Query:
Query = "UPDATE SortingIndices
SET X_Centroid_Sort_Index = (CASE
WHEN Sort_ID = 1 THEN 1.4324
WHEN Sort_ID = 2 THEN 4.234
WHEN Sort_ID = 3 THEN 324
...
WHEN Sort_ID = 1000 THEN 232.4 END);