No, as far as I am aware we did not invent some secret engineering sauce in the 1970's or whenever to suddenly annul the cost difference of a multiplication unit and a bit shifter. A general multiplication, in terms of logical gates, and certainly in terms of logical operations, is still more complex than a shift with a barrel shifter in many scenarios, on many architectures. How this translates into overall runtime on a desktop computer may be a bit opaque. I do not know for sure how they are implemented in specific processors, but here is an explanation of a multiplication: Is integer multiplication really same speed as addition on modern CPUIs integer multiplication really same speed as addition on modern CPU
No, as far as I am aware we did not invent some secret engineering sauce in the 1970's or whenever to suddenly annul the cost difference of a multiplication unit and a bit shifter. A general multiplication, in terms of logical gates, and certainly in terms of logical operations, is still more complex than a shift with a barrel shifter in many scenarios, on many architectures. How this translates into overall runtime on a desktop computer may be a bit opaque. I do not know for sure how they are implemented in specific processors, but here is an explanation of a multiplication: Is integer multiplication really same speed as addition on modern CPU
No, as far as I am aware we did not invent some secret engineering sauce in the 1970's or whenever to suddenly annul the cost difference of a multiplication unit and a bit shifter. A general multiplication, in terms of logical gates, and certainly in terms of logical operations, is still more complex than a shift with a barrel shifter in many scenarios, on many architectures. How this translates into overall runtime on a desktop computer may be a bit opaque. I do not know for sure how they are implemented in specific processors, but here is an explanation of a multiplication: Is integer multiplication really same speed as addition on modern CPU
So what if the shift is faster than the multiplication? There are certainly indications why that would be true. GCC, as you can see above, appears to think (even without optimization) that avoiding direct multiplication in favor of other instructions is a good idea. The "Intel 64 and IA-32 Architectures Optimization Reference Manual"
http://www.intel.com/content/www/us/en/processors/architectures-software-developer-manuals.html Intel 64 and IA-32 Architectures Optimization Reference Manual will give you an idea of the relative cost of CPU instructions. Another resource, more focused on instruction latency and throughput, is http://www.agner.org/optimize/instruction_tables.pdf. Note that they are not a good predicator of absolute runtime, but of performance of instructions relative to each other. In a tight loop, as your test is simulating, the metric of "throughput" should be most relevant. It is the number of cycles that an execution unit will typically be tied up for when executing a given instruction.
No, as far as I am aware we did not invent some secret engineering sauce in the 1970's or whenever to suddenly annul the cost difference of a multiplication unit and a bit shifter. A general multiplication, in terms of logical gates, and certainly in terms of logical operations, is still more complex than a shift with a barrel shifter in many scenarios, on many architectures. How this translates into overall runtime on a desktop computer may be a bit opaque. I do not know for sure how they are implemented in specific processors, but here is an explanation of a multiplication:
http://stackoverflow.com/questions/21819682/is-integer-multiplication-really-same-speed-as-addition-on-modern-cpu While here is an explanation of a Barrel Shifter: http://en.wikipedia.org/wiki/Barrel_shifter. The documentsNo, as far as I have referencedam aware we did not invent some secret engineering sauce in the previous paragraph give another view on1970's or whenever to suddenly annul the relative cost difference of operationsa multiplication unit and a bit shifter. A general multiplication, by proxyin terms of CPU instructionslogical gates, and certainly in terms of logical operations, is still more complex than a shift with a barrel shifter in many scenarios, on many architectures. The engineers over at Intel frequently seem to get similar questionsHow this translates into overall runtime on a desktop computer may be a bit opaque. I do not know for sure how they are implemented in specific processors, but here is an explanation of a multiplication: Is integer multiplication really same speed as addition on modern CPU
https://software.intel.com/en-us/forums/topic/299987?language=it While here is an explanation of a Barrel Shifter. The documents I have referenced in the previous paragraph give another view on the relative cost of operations, by proxy of CPU instructions. The engineers over at Intel frequently seem to get similar questions: intel developer zone forums clock cycles for integer multiplication and addition in core 2 duo processor
So what if the shift is faster than the multiplication? There are certainly indications why that would be true. GCC, as you can see above, appears to think (even without optimization) that avoiding direct multiplication in favor of other instructions is a good idea. The "Intel 64 and IA-32 Architectures Optimization Reference Manual"
http://www.intel.com/content/www/us/en/processors/architectures-software-developer-manuals.html will give you an idea of the relative cost of CPU instructions. Another resource, more focused on instruction latency and throughput, is http://www.agner.org/optimize/instruction_tables.pdf. Note that they are not a good predicator of absolute runtime, but of performance of instructions relative to each other. In a tight loop, as your test is simulating, the metric of "throughput" should be most relevant. It is the number of cycles that an execution unit will typically be tied up for when executing a given instruction.
No, as far as I am aware we did not invent some secret engineering sauce in the 1970's or whenever to suddenly annul the cost difference of a multiplication unit and a bit shifter. A general multiplication, in terms of logical gates, and certainly in terms of logical operations, is still more complex than a shift with a barrel shifter in many scenarios, on many architectures. How this translates into overall runtime on a desktop computer may be a bit opaque. I do not know for sure how they are implemented in specific processors, but here is an explanation of a multiplication:
http://stackoverflow.com/questions/21819682/is-integer-multiplication-really-same-speed-as-addition-on-modern-cpu While here is an explanation of a Barrel Shifter: http://en.wikipedia.org/wiki/Barrel_shifter. The documents I have referenced in the previous paragraph give another view on the relative cost of operations, by proxy of CPU instructions. The engineers over at Intel frequently seem to get similar questions:
https://software.intel.com/en-us/forums/topic/299987?language=it So what if the shift is faster than the multiplication? There are certainly indications why that would be true. GCC, as you can see above, appears to think (even without optimization) that avoiding direct multiplication in favor of other instructions is a good idea. The Intel 64 and IA-32 Architectures Optimization Reference Manual will give you an idea of the relative cost of CPU instructions. Another resource, more focused on instruction latency and throughput, is http://www.agner.org/optimize/instruction_tables.pdf. Note that they are not a good predicator of absolute runtime, but of performance of instructions relative to each other. In a tight loop, as your test is simulating, the metric of "throughput" should be most relevant. It is the number of cycles that an execution unit will typically be tied up for when executing a given instruction.
No, as far as I am aware we did not invent some secret engineering sauce in the 1970's or whenever to suddenly annul the cost difference of a multiplication unit and a bit shifter. A general multiplication, in terms of logical gates, and certainly in terms of logical operations, is still more complex than a shift with a barrel shifter in many scenarios, on many architectures. How this translates into overall runtime on a desktop computer may be a bit opaque. I do not know for sure how they are implemented in specific processors, but here is an explanation of a multiplication: Is integer multiplication really same speed as addition on modern CPU
While here is an explanation of a Barrel Shifter. The documents I have referenced in the previous paragraph give another view on the relative cost of operations, by proxy of CPU instructions. The engineers over at Intel frequently seem to get similar questions: intel developer zone forums clock cycles for integer multiplication and addition in core 2 duo processor
No, as far as I am aware we did not invent some secret engineering sauce in the 1970's or whenever to suddenly annul the cost difference of a multiplication unit and a bit shifter. MultiplicationA general multiplication, in terms of logical gates, and certainly in terms of logical operations, is still more complex than a shift with a barrel shifter in many scenarios, on many architectures. How this translates into overall runtime on a desktop computer may be a bit opaque. I do not know for sure how they are implemented in specific processors, but here is an explanation of a multiplication:
No, as far as I am aware we did not invent some secret engineering sauce in the 1970's or whenever to suddenly annul the cost difference of a multiplication unit and a bit shifter. Multiplication, in terms of logical gates, and certainly in terms of logical operations, is still more complex than a shift. How this translates into overall runtime on a desktop computer may be a bit opaque. I do not know for sure how they are implemented in specific processors, but here is an explanation of a multiplication:
No, as far as I am aware we did not invent some secret engineering sauce in the 1970's or whenever to suddenly annul the cost difference of a multiplication unit and a bit shifter. A general multiplication, in terms of logical gates, and certainly in terms of logical operations, is still more complex than a shift with a barrel shifter in many scenarios, on many architectures. How this translates into overall runtime on a desktop computer may be a bit opaque. I do not know for sure how they are implemented in specific processors, but here is an explanation of a multiplication:
Loading
lang-c