{"id":20267,"date":"2022-11-09T05:16:29","date_gmt":"2022-11-08T23:46:29","guid":{"rendered":"https:\/\/jassweb.com\/solved\/solved-why-does-this-float-have-2-different-values\/"},"modified":"2022-11-09T05:16:29","modified_gmt":"2022-11-08T23:46:29","slug":"solved-why-does-this-float-have-2-different-values","status":"publish","type":"post","link":"https:\/\/jassweb.com\/solved\/solved-why-does-this-float-have-2-different-values\/","title":{"rendered":"[Solved] Why does this float have 2 different values?"},"content":{"rendered":"

[ad_1]
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Your code isn’t C, but this is:<\/p>\n

#include <stdio.h>\n\nint main ()\n{\n        float add = 0;\n        int count[] = { 3, 2, 1, 3, 1, 2, 3, 3, 1, 2, 1 };\n        for (int i = 0; i < 11; i++) {\n                add += 1 \/ ((float) count[i] + 1);\n        }\n        printf(\"%f\\n\", add);\n        return 0;\n}\n<\/code><\/pre>\n
I’ve executed this code with add += 1 \/ ((float) count[i] + 1);<\/code> and add += 1.0 \/ ((float) count[i] + 1);<\/code>.<\/p>\n
In both cases, printf(\"%f\\n\", add);<\/code> prints 4.000000<\/code>.<\/p>\n
However, when I print each bit of the variable add<\/code>, it gives me 01000000011111111111111111111111<\/code> (3.9999998) and 01000000100000000000000000000000<\/code> (4)<\/p>\n
As pointed by phuclv, this is because 1.0<\/code> is a double<\/code>, hence the calculation is done with double precision, whereas when using 1<\/code>, the calculation is done using single precision (because of the cast to float).<\/p>\n
If you replace the cast to double<\/code> in the first equation or if you change 1.0<\/code> into 1.0f<\/code> in the second equation, you’ll obtain the same result.<\/p>\n<\/p><\/div>\n
<\/div>\n<\/div>\n
            2<\/span> <\/p><\/div>\n<\/div>\n
[ad_2]<\/p>\n
solved Why does this float have 2 different values? <\/p>\n","protected":false},"excerpt":{"rendered":"
[ad_1] Your code isn’t C, but this is: #include <stdio.h> int main () { float add = 0; int count[] = { 3, 2, 1, 3, 1, 2, 3, 3, 1, 2, 1 }; for (int i = 0; i < 11; i++) { add += 1 \/ ((float) count[i] + 1); } printf(“%f\\n”, add); … Read more<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[320],"tags":[324,359,652],"class_list":["post-20267","post","type-post","status-publish","format-standard","hentry","category-solved","tag-c","tag-floating-point","tag-int"],"yoast_head":"\n[Solved] Why does this float have 2 different values? - JassWeb<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/jassweb.com\/solved\/solved-why-does-this-float-have-2-different-values\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"[Solved] Why does this float have 2 different values? - JassWeb\" \/>\n<meta property=\"og:description\" content=\"[ad_1] Your code isn’t C, but this is: #include <stdio.h> int main () { float add = 0; int count[] = { 3, 2, 1, 3, 1, 2, 3, 3, 1, 2, 1 }; for (int i = 0; i < 11; i++) { add += 1 \/ ((float) count[i] + 1); } printf("%fn", add); ... 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