Why qt execution is so slow,this is a test

[wysota]

By the way... the "C++ test" is flawed. First of all the only "C++" thing in it is using "new" and "delete" instead of "malloc" and "free" and second of all all the other "tests" increment the buffer char by char instead of preallocating everything at once.

Here is a more proper test of this useless case and the results. If you analyze the results, you'll see what takes the most time and how to counteract it.

********* Start testing of StringTest *********
Config: Using QTest library 4.7.4, Qt 4.7.4
PASS   : StringTest::initTestCase()
RESULT : StringTest::testC():
     16 msecs per iteration (total: 66, iterations: 4)
PASS   : StringTest::testC()
RESULT : StringTest::testCPreallocated():
     0.60 msecs per iteration (total: 77, iterations: 128)
PASS   : StringTest::testCPreallocated()
RESULT : StringTest::testCPP():
     112,716 msecs per iteration (total: 112,716, iterations: 1)
PASS   : StringTest::testCPP()
RESULT : StringTest::testCPPPreallocated():
     0.63 msecs per iteration (total: 81, iterations: 128)
PASS   : StringTest::testCPPPreallocated()
RESULT : StringTest::testCPPString():
     4.3 msecs per iteration (total: 70, iterations: 16)
PASS   : StringTest::testCPPString()
RESULT : StringTest::testByteArray():
     5.8 msecs per iteration (total: 94, iterations: 16)
PASS   : StringTest::testByteArray()
RESULT : StringTest::testByteArrayPreallocated():
     2.7 msecs per iteration (total: 89, iterations: 32)
PASS   : StringTest::testByteArrayPreallocated()
RESULT : StringTest::testByteArrayPrefilled():
     0.11 msecs per iteration (total: 60, iterations: 512)
PASS   : StringTest::testByteArrayPrefilled()
RESULT : StringTest::testQString():
     10 msecs per iteration (total: 80, iterations: 8)
PASS   : StringTest::testQString()
RESULT : StringTest::testQStringPreallocated_reserve():
     9.3 msecs per iteration (total: 75, iterations: 8)
PASS   : StringTest::testQStringPreallocated_reserve()
RESULT : StringTest::testQStringPreallocated_resize():
     7.6 msecs per iteration (total: 61, iterations: 8)
PASS   : StringTest::testQStringPreallocated_resize()
RESULT : StringTest::testQStringPrefilled():
     1.0 msecs per iteration (total: 65, iterations: 64)
PASS   : StringTest::testQStringPrefilled()
PASS   : StringTest::cleanupTestCase()
Totals: 14 passed, 0 failed, 0 skipped
********* Finished testing of StringTest *********

********* Start testing of StringTest *********
Config: Using QTest library 4.7.4, Qt 4.7.4
PASS   : StringTest::initTestCase()
RESULT : StringTest::testC():
     16 msecs per iteration (total: 66, iterations: 4)
PASS   : StringTest::testC()
RESULT : StringTest::testCPreallocated():
     0.60 msecs per iteration (total: 77, iterations: 128)
PASS   : StringTest::testCPreallocated()
RESULT : StringTest::testCPP():
     112,716 msecs per iteration (total: 112,716, iterations: 1)
PASS   : StringTest::testCPP()
RESULT : StringTest::testCPPPreallocated():
     0.63 msecs per iteration (total: 81, iterations: 128)
PASS   : StringTest::testCPPPreallocated()
RESULT : StringTest::testCPPString():
     4.3 msecs per iteration (total: 70, iterations: 16)
PASS   : StringTest::testCPPString()
RESULT : StringTest::testByteArray():
     5.8 msecs per iteration (total: 94, iterations: 16)
PASS   : StringTest::testByteArray()
RESULT : StringTest::testByteArrayPreallocated():
     2.7 msecs per iteration (total: 89, iterations: 32)
PASS   : StringTest::testByteArrayPreallocated()
RESULT : StringTest::testByteArrayPrefilled():
     0.11 msecs per iteration (total: 60, iterations: 512)
PASS   : StringTest::testByteArrayPrefilled()
RESULT : StringTest::testQString():
     10 msecs per iteration (total: 80, iterations: 8)
PASS   : StringTest::testQString()
RESULT : StringTest::testQStringPreallocated_reserve():
     9.3 msecs per iteration (total: 75, iterations: 8)
PASS   : StringTest::testQStringPreallocated_reserve()
RESULT : StringTest::testQStringPreallocated_resize():
     7.6 msecs per iteration (total: 61, iterations: 8)
PASS   : StringTest::testQStringPreallocated_resize()
RESULT : StringTest::testQStringPrefilled():
     1.0 msecs per iteration (total: 65, iterations: 64)
PASS   : StringTest::testQStringPrefilled()
PASS   : StringTest::cleanupTestCase()
Totals: 14 passed, 0 failed, 0 skipped
********* Finished testing of StringTest *********

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