From: "Alfredo J. Cole" To: Subject: Round off errors Date: Fri, 20 Feb 1998 08:30:41 -0600 Message-ID: <01bd3e0c$200881c0$LocalHost@alfredoc> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Precedence: bulk Compiling the following code with DJGPP gives the erroneous result (5551.20). The same code compiled with Borland's bcd class gives the correct result (5551.22). I am developing an accounting system with DJGPP and it requires that the results be exact. Is there a similar class or option under DJGPP that will eliminate these round off errors? Thank you. ------------------------------ /* Example of round-off error */ /* When this program is executed with IEEE binary floating point arithmetic, the answer is incorrect due to accumulated round-off error. When BCD is used, the correct answer is obtained. */ #include float data[100] = { 4997.01, 921.05, -1921.06, 4621.03, -605.20, -3105.12, 4665.01, -271.23, -212.23, -1548.18, -2351.12, -2787.12, 1474.19, 1817.07, -2299.12, 2648.13, -3787.12, 3948.13, -3401.12, 170.14, 4030.14, -334.22, -704.20, -2233.12, 3369.13, -4218.24, 2214.13, -4707.24, 2369.13, 4816.01, -4009.12, 332.15, 4501.01, -1349.18, -438.22, -4996.24, 4020.13, -2623.12, 2541.13, -608.20, 3929.14, -3300.12, -4314.24, 839.16, 2173.14, 1243.07, -2291.12, 693.16, 4061.14, -2625.12, -4048.12, 2162.13, 686.05, 2133.13, -2149.12, 3884.13, -199.24, -3611.12, 3282.13, -95.24, -4614.24, 1875.07, 2203.13, -1371.18, -1616.06, 1210.07, -3014.12, 4197.01, -4141.24, 3255.13, -3203.12, 547.16, 2713.14, -1039.18, 982.05, -1924.06, 3419.13, -2488.12, 4334.03, -4469.24, 4088.14, -3840.12, 585.05, -1932.06, 4496.01, -918.20, -445.22, -1856.18, 2007.07, -2631.12, 351.03, 774.05, 84.01, -1089.06, 4278.01, -4860.24, 1165.07, 4482.03, -8.23, -3432.12 }; int main () { /* add 100 numbers and print the result */ /* In this example, the array is initialized to contain the data. In real programs the data might be read from a file or the keyboard using scanf. */ float answer = 0.0; int i; for (i = 0; i < 100; ++i) answer += data[i]; printf("The sum is %10.2f\n",answer); printf("The correct answer is 5551.22\n"); return 0; } ------------------------------ -- Alfredo J. Cole ACyC (ajc AT acyc DOT com) Tegucigalpa, Honduras Phone: +(504) 265902 Fax: +(504) 267672 http://www.acyc.com