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It does use floating point. I think the slide was misleading. http://www.netlib.org/blas/blast-forum/cblas.h http://www.netlib.org/blas/blast-forum/cblas.h

by minimax 12y ago

acqq 12y ago
BLAS uses it, and Excel of course also uses floating point. On the first look, it appears a dubious presentation anyway. The examples don't have much sense too: you can't actually calculate properly sin( 10e22 ) in binary floating point format because both exponent and mantissa are binary: the exponent is 2^76 and in 4-bytes floats you have 23 bits, in 8-byte doubles 53 bits, so you can't even represent the starting number with the enough bits to calculate meaningful sin. You'd need a two parameter function to be even able to pass what you actually want to pass. So calling sin( 10e22 ) in the languages with 4 or 8-bytes binary FP of course can't be expected to produce any meaningful result. But maybe all this was spoken, not written, and it's just misleading to read it without knowing the comments. "Who is NOT using: Excel, BLAS" could maybe then mean that author wanted to say "Excel, BLAS, they use them too"? (If we want to believe that he had any idea what he wrote about). Definitely not good to give this presentation to somebody who doesn't already know more. Confusion guaranteed.
- stephencanon 12y ago
  Paul Zimmermann certainly knows that BLAS and Excel use floating-point. I assume that the spoken content of the presentation made the meaning of those slides much clearer; it’s too bad that the slides are being discussed in a vacuum. Also 1e22 (note: not 10e22) is exactly representable in double (though not in float). Specifically, it is exactly equal to: 1.000011110000110011110000011001001101110101011001001 * 2^73 which requires only a 52 bit significand.
  - acqq 12y ago
    You are absolutely right, 1e22 fits in the double, exactly with the bit pattern you showed. And it doesn't fit in the float. Thanks. One more proof that PDF alone is too little of the presentation and that it's easy for the reader to remain confused. I consider your reply "a missing slide" between p 15 and p 16. So the author is: http://en.wikipedia.org/wiki/Paul_Zimmermann http://en.wikipedia.org/wiki/Paul_Zimmermann

It does use floating point. I think the slide was misleading. http://www.netlib.org/blas/blast-forum/cblas.h http://www.netlib.org/blas/blast-forum/cblas.h

by minimax 12y ago

It does use floating point. I think the slide was misleading. http://www.netlib.org/blas/blast-forum/cblas.h http://www.netlib.org/blas/blast-forum/cblas.h

acqq 12y ago

BLAS uses it, and Excel of course also uses floating point. On the first look, it appears a dubious presentation anyway. The examples don't have much sense too: you can't actually calculate properly sin( 10e22 ) in binary floating point format because both exponent and mantissa are binary: the exponent is 2^76 and in 4-bytes floats you have 23 bits, in 8-byte doubles 53 bits, so you can't even represent the starting number with the enough bits to calculate meaningful sin. You'd need a two parameter function to be even able to pass what you actually want to pass. So calling sin( 10e22 ) in the languages with 4 or 8-bytes binary FP of course can't be expected to produce any meaningful result. But maybe all this was spoken, not written, and it's just misleading to read it without knowing the comments. "Who is NOT using: Excel, BLAS" could maybe then mean that author wanted to say "Excel, BLAS, they use them too"? (If we want to believe that he had any idea what he wrote about). Definitely not good to give this presentation to somebody who doesn't already know more. Confusion guaranteed.

stephencanon 12y ago
Paul Zimmermann certainly knows that BLAS and Excel use floating-point. I assume that the spoken content of the presentation made the meaning of those slides much clearer; it’s too bad that the slides are being discussed in a vacuum. Also 1e22 (note: not 10e22) is exactly representable in double (though not in float). Specifically, it is exactly equal to: 1.000011110000110011110000011001001101110101011001001 * 2^73 which requires only a 52 bit significand.
- acqq 12y ago
  You are absolutely right, 1e22 fits in the double, exactly with the bit pattern you showed. And it doesn't fit in the float. Thanks. One more proof that PDF alone is too little of the presentation and that it's easy for the reader to remain confused. I consider your reply "a missing slide" between p 15 and p 16. So the author is: http://en.wikipedia.org/wiki/Paul_Zimmermann http://en.wikipedia.org/wiki/Paul_Zimmermann